Repaired Harbor Freight digital caliper

[P E Schoen]

I have two Harbor Freight digital calipers, item #47257, and I've had
problems with one of them especially, where the display will go blank. It
seemed to work sometimes if I squeezed the enclosure, and I thought it was a
bad battery or bad connection. But a fresh battery didn't work.

So I took it apart, which meant peeling off a foil backing to expose four
small phillips head screws, which removed the electronics module, and then I
removed the PC board with four even smaller phillips screws. The LCD display
connects to the board with a flexible conductive strip, which relies on
pressure to maintain contact. I cleaned it and the mating contacts on the
PCB, reassembled it, and it now works fine!

My house is always very humid and I think that's what caused the problem.
It's hell on all my tools. Everything is rusty or mildewed.

It's quite interesting to see the mechanism that is used to make
measurements. There is an array of PCB traces that are aligned with an array
of stripes along the length of the caliper, and (I assume) these create
pulses that are counted as the head is moved. But it also needs to know
which way the head is being moved. Probably something like a quadrature
encoder as used for rotary position sensing. I'll have to look it up.

Paul

[Jim Yanik]

"P E Schoen" <pa...@pstech-inc.com> wrote in
news:a4_xq.6861$ov2....@newsfe10.iad:

use Boeing Boeshield T-9 to prevent the rusting of your tools.

I wonder if Cramolin/DeOxit would work on the conductive strip?

--
Jim Yanik
jyanik
at
localnet
dot com

[Jeff Liebermann]

On Sat, 19 Nov 2011 22:19:11 -0600, Jim Yanik <jya...@abuse.gov>
wrote:

>I wonder if Cramolin/DeOxit would work on the conductive strip?

<http://siber-sonic.com/electronics/caig.html>
Sorta. The original Cramolin contained about 5% oleic acid, which is
great for removing surface oxidation, but is also mildly corrosive to
copper. The current version is DeOxit from Caig Labs. It comes in an
amazing variety of forms, and is allegedly non-corrosive.
<http://store.caig.com/s.nl/sc.2/.f>
The MSDS data shows the active ingredients as a "trade secret". Oh
well.

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[N_Cook]

P E Schoen <pa...@pstech-inc.com> wrote in message
news:a4_xq.6861$ov2....@newsfe10.iad...

++++

It is usually a Moire fringe counting mechanism. The system like when you
move along a street and look through a set of railings to another set of
railings and you see a moving "interference" pattern. Set 2 fine grills over
one another at slight relative angle and these fringes become wide enough to
be reliably counted by a relatively large opto device, 10 or more times
wider than the spacing between the grating lines

[William Sommerwerck]

"Jim Yanik" <jya...@abuse.gov> wrote in message
news:Xns9FA2ED4AFED51...@216.168.3.44...

> I wonder if Cramolin/DeOxit would work on the conductive strip?

I assume the strip is carbon-impregnated rubber (or some synthetic polymer).
Cramolin/DeOxit remove surface oxidation. I don't the latter as being
compatible with the former.

[amdx]

On 11/19/2011 9:01 PM, P E Schoen wrote:
> I have two Harbor Freight digital calipers, item #47257, and I've had
> problems with one of them especially, where the display will go blank.
> It seemed to work sometimes if I squeezed the enclosure, and I thought
> it was a bad battery or bad connection. But a fresh battery didn't work.
>

That's why I like the Dial calipers vs Digital Calipers, no concern
about batteries or electronics.
(Dial Calipers, Item # 66541, Out of Stock)

Although a couple years ago HF had the 6" Digital calipers on sale for
$9.99, I bought two. They are still in the boxes and I use my Dial
calipers. I think I might give one away as a Christmas present.
Mikek

[N_Cook]

amdx <am...@knologynotthis.net> wrote in message
news:4756b$4ec8f55d$18ec6dd7$12...@KNOLOGY.NET...

I've never used the new-fangled ones - do you have to do a clean jaws, close
jaws, zero calibration check/0 reset ,every time you use them ? as the count
must be lost each time it is switched off

[Stormin Mormon]

Cleaned, how? Trichlor? WD? Cotton swab?

Have you considered something to reduce the humidity, like
vent fan, central AC, or dehumidifier?

--
Christopher A. Young
Learn more about Jesus
www.lds.org
.

"P E Schoen" <pa...@pstech-inc.com> wrote in message
news:a4_xq.6861$ov2....@newsfe10.iad...

[Dave Plumpe]

Not only do they remember where Zero is, they even keep track of any
movement that occurs while they're turned off. Smart little devils.

I find myself more & more reaching for the digital ones for the ease of
swapping between inches & millimeters.

-Dave
--
http://plumpe.home.mindspring.com
email: last...@mindspring.com
ANTI-SPAM: To email, replace "lastname" with "plumpe"
"N_Cook" <div...@tcp.co.uk> wrote in message
news:jaatmo$4n4$1...@dont-email.me...

[sta...@prolynx.com]

On Nov 20, 6:03 am, "N_Cook" <dive...@tcp.co.uk> wrote:
> amdx <a...@knologynotthis.net> wrote in message

Used to be, they've improved things. On at least some, the count is
kept live and just the display is switched off. It all goes away when
batteries are switched, but that can be lived with.

Stan

[gree...@neo.rr.com]

On Sun, 20 Nov 2011 06:41:03 -0600, amdx <am...@knologynotthis.net>
wrote:

I bought one of those and really like it. It seems comparable to
calipers costing many time more. The only problem is I have to remove
the battery when I am done using it or it is dead the next time I get
it out. I have a feeling that is why they were selling them for
$9.99. Fortuneately, it is easy to remove and reinsert the battery.

[N_Cook]

Dave Plumpe <last...@mindspring.com> wrote in message
news:dcCdnbxH1tldnVTT...@earthlink.com...

An engineer told me never close the jaws of a micrometer or vernier calipers
for storage, leave the jaws open slightly. Do these digitally things require
the jaws closing before switching off ? How do they know of any movement of
the jaws when switched off elsewise?

[N_Cook]

<sta...@prolynx.com> wrote in message
news:0156c7a7-8bb2-4f32...@u6g2000vbg.googlegroups.com...

+++

So that explains , down thread, the drawback of dying batteries when
switched "off"

[Jamie]

I have the HF digital calipers and I need to pull the battery when not
in use other wise, it'll be dead next time I need it. It seems to drain
quite fast.

Other than that, it seems to work very nicely..
Jamie

[Jamie]

And the engineer was correct in saying so.

Jamie

[Doug White]

gree...@neo.rr.com wrote in
news:e70ic7h9g57un7sii...@4ax.com:

The battery life in even high end calipers is highly variable. I have a
couple Mitutoyo calipers that are pretty good, but some of their
micrometers are terrible. I have an SPI micrometer that looks
suspiciously like a Chinese cheapo I have. They both need to have the
battery removed if you aren't actively using them. The SPI is a 24" job,
so it rarely gets used. There is no way the battery would last if I left
it in palce.

I discovered the hard way that the little cube electronic levels also eat
batteries, and they require a diet of the larger more expensive coin
cells (2032?). Most of my electronic measuring widgets use 357 style
button cells, and I buy them in quantity off eBay. Radio Shack is a real
ripoff for those things.

Doug White

[Jeff Liebermann]

On Sun, 20 Nov 2011 13:38:36 -0000, "N_Cook" <div...@tcp.co.uk>
wrote:

>An engineer told me never close the jaws of a micrometer or vernier calipers
>for storage, leave the jaws open slightly.

True. With gear type calipers, the lubricating grease tends to
migrate to that position. If a sufficiently filthy environment, an
lump of dirt encrusted grease will be left in that position. If it
happens to be at 0.0, then it will be difficult to accurately
calibrate the mechanism. There are also some minor reasons, such as
the tendency for two parallel surfaces to trap moisture between them
and rust.

>Do these digitally things require
>the jaws closing before switching off ?

No.

>How do they know of any movement of
>the jaws when switched off elsewise?

Only the display is turned off. The pulse counting mechanism is still
operating and functional. The downside is that the battery will be
dead in about 6-9 months. Most include a spare LR44 battery. I had
to buy a pile of them to keep my calipers going. Somehow, the battery
is usually dead when I need to use them.

50 batteries for $3.75
<http://www.ebay.com/itm/220751739681>

I have an expensive set of Starett calipers (both metric and US). I
use them more often than the electronic variety, mostly out of habit.
My most useful measuring tools are my 6" pocket steel scale and a tape
measure.

[Bob Engelhardt]

Jamie wrote:
> I have the HF digital calipers and I need to pull the battery when not
> in use other wise, it'll be dead next time I need it. It seems to drain
> quite fast.

...

I have one & the battery lasts quite a while (doesn't get used much).
Maybe a different model. Or a different batch. Or different spots on
the quality curve <G>.

Bob

[dagmarg...@yahoo.com]

http://www.biotele.com/digital_caliper.htm

--
Cheers,
James Arthur

[Martin Riddle]

"amdx" <am...@knologynotthis.net> wrote in message
news:4756b$4ec8f55d$18ec6dd7$12...@KNOLOGY.NET...

I have a vernier Calipe. I never need to set the dial, cause there isn't
one ;)

Cheers

[dagmarg...@yahoo.com]

Silver oxide batteries cost a bunch more, but last twice as long.

Full details: http://www.fliptronics.com/tip0006.html

--
Cheers,
James Arthur

[Gunner Asch]

On Sun, 20 Nov 2011 08:29:39 -0500, "Dave Plumpe"
<last...@mindspring.com> wrote:

>Not only do they remember where Zero is, they even keep track of any
>movement that occurs while they're turned off. Smart little devils.
>
>I find myself more & more reaching for the digital ones for the ease of
>swapping between inches & millimeters.
>
>-Dave

As do I.

My Mitytoyo digital mics..never could figure out how they work
though..Ive got one thats had the same battery in it for 4 yrs so
far..still reading just fine and its always displaying whenever I open
the box

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

[Gunner Asch]

On Sun, 20 Nov 2011 16:23:32 GMT, Doug White <gwh...@alum.mit.edu>
wrote:

>I discovered the hard way that the little cube electronic levels also eat
>batteries, and they require a diet of the larger more expensive coin
>cells (2032?).

Just a heads up..a lot of the local 99c stores sell a card with 3 to 5
of the 2032s for ....99c

I buy a couple cards every year just to have them on hand

[Too_Many_Tools]

Interesting..it sounds like you may have a serious mold problem.

It can destroy a house if left untended.

TMT

[mike]

Gunner Asch wrote:
> On Sun, 20 Nov 2011 08:29:39 -0500, "Dave Plumpe"
> <last...@mindspring.com> wrote:
>
>> Not only do they remember where Zero is, they even keep track of any
>> movement that occurs while they're turned off. Smart little devils.
>>
>> I find myself more & more reaching for the digital ones for the ease of
>> swapping between inches & millimeters.
>>
>> -Dave
>
> As do I.
>
> My Mitytoyo digital mics..never could figure out how they work
> though..Ive got one thats had the same battery in it for 4 yrs so
> far..still reading just fine and its always displaying whenever I open
> the box
>
> Gunner

Same here.
I bought several of the Harbor Freight ones back when they were on sale.
They're always dead. I have to take the battery out when not in use.
PITA, but I'm gonna have to replace it anyway if I leave it in.

My Mitutoyo has been going strong for years on the same battery.

[P E Schoen]

"Stormin Mormon" wrote in message news:jaaun0$a9m$1...@dont-email.me...

> Cleaned, how? Trichlor? WD? Cotton swab?

I used rubbing alcohol, which I also use for defluxing PCBs. I also scraped
the surface and dried it with a paper towel.

> Have you considered something to reduce the humidity,
> like vent fan, central AC, or dehumidifier?

I've lived with the problem for a long time. I have two houses, adjacent to
each other, and the lower levels have a stone foundations built into a hill.
It is worse in the house where I have my workshop and storage. And the
houses are in a low-lying area under lots of trees and the water table is
close to the surface. I've also had leaks in the foundation as well as the
roof so moisture has gotten in. Some time ago I basically gutted both houses
and replaced the old rotten frame studs and mud sills with new
pressure-treated lumber, but did not add vapor barrier, insulation, or new
drywall, until recently, and only partially. Being below grade, it's like
being in a cave, and it's often so cold that a dehumidifier freezes up. And
without insulation and vapor barrier, it's almost futile to try.

You can see my houses, and some of the work I've done (and some of my
tools), on youtube:
http://www.youtube.com/PaulAndMuttley#p/u/50/oxKL2p8O3EM
(there are also part 2 and part 3)

Paul
www.muttleydog.com

[gregz]

Jeff Liebermann <je...@cruzio.com> wrote:
> On Sat, 19 Nov 2011 22:19:11 -0600, Jim Yanik <jya...@abuse.gov>
> wrote:
>
>> I wonder if Cramolin/DeOxit would work on the conductive strip?
>
> <http://siber-sonic.com/electronics/caig.html>
> Sorta. The original Cramolin contained about 5% oleic acid, which is
> great for removing surface oxidation, but is also mildly corrosive to
> copper. The current version is DeOxit from Caig Labs. It comes in an
> amazing variety of forms, and is allegedly non-corrosive.
> <http://store.caig.com/s.nl/sc.2/.f>
> The MSDS data shows the active ingredients as a "trade secret". Oh
> well.

I never have been able to get much visible effect of so called corrosion
removers. Oleic acid probably being best, but supposedly the cramolin
chemist also had input on making deoxit. On a short term test I can visibly
wipe off oxide with an alcohol swipe, being just as effective. Most of the
removing is mechanical in nature, and any liquid helps.

Greg

[Ron D.]

I have a cheap Caliper too and it recently went flakey.

I did my standard trick: Remove battery. Short battery contacts:
Insert new battery. Worked.

Mine uses an LR44 and you HAVE TO use an LR44, not a substitute
battery that you can get a Radio Shack.
Mechanically they are not the same.

[Rich Webb]

On Sun, 20 Nov 2011 23:47:58 +0000 (UTC), gregz <ze...@comcast.net>
wrote:

I tried a paste of cream of tartar from the spice rack in the kitchen on
the battery terminals on a long forgotten remote control that had spewed
its battery guts to make a nasty, green mess of the copper-nickel
strips. Worked amazingly well, better than anything else I've tried for
that particular problem. YMMV, of course.

--
Rich Webb Norfolk, VA

[Jeff Liebermann]

On Sun, 20 Nov 2011 23:47:58 +0000 (UTC), gregz <ze...@comcast.net>
wrote:

The oleic acid is only about 5% of the contact cleaner. Over a period
of time, it will help remove any oxide deposits. However, at such a
low concentration, it should not be expected to dissolve a substantial
oxide accumulation. Basically, any detergent will do as well if you
can live with the residue.

More on Cramolin:
<http://www.pitt.edu/~szekeres/caigcram.htm>
<http://siber-sonic.com/electronics/caig.html>

Cleaning brass clocks. Note the section on oleic acid.
<http://www.abbeyclock.com/brass2.html>
The oleic acid therefore has two functions: to remove
the oxide layer from the metals and to act as a soap
to remove the dirt and oils. The cleaning solution
has about 90% ammonia solution with about 5% oleic
acid and 5% acetone added, thereby leaving plenty
of excess ammonia molecules to keep the solution
alkaline.
The acetone is to accelerate evaporation. Oleic acid also has the
advantage of being common, cheap, and non-toxic. It's a by product of
corn and veggie oil production.

<http://www.dialcover.com/components.html>
Scroll down to "Cease and Desist" contact cleaner. Much the same as
my home made formula except I won't use acetone because it eats
plastic. Ordinary isopropyl alcohol is safer.

Homebrew cleaners and protectors:
<http://www.pitt.edu/~szekeres/cleaner.htm>
The comments on the effects of silicones plus salt in WD40 are
interesting.

[Jeff Liebermann]

On Sun, 20 Nov 2011 16:47:25 -0800 (PST), "Ron D."
<ron.d...@gmail.com> wrote:

>I have a cheap Caliper too and it recently went flakey.
>
>I did my standard trick: Remove battery. Short battery contacts:
>Insert new battery. Worked.

My cheap electronic caliper goes nuts when I transmit on UHF anywhere
near it. However, it doesn't require the battery removal ordeal to
recover. I just reset to zero and continue.

>Mine uses an LR44 and you HAVE TO use an LR44, not a substitute
>battery that you can get a Radio Shack.
>Mechanically they are not the same.

I beg to differ. The general package name is LR44 in an 11.6mm dia x
5.4mm thick package alkaline cell. There are slight variations, but
the IEC LR1154 equivalents (LR44/LR154, A76, 157/303/357) are all the
same size. Where you can have problems is that the SR44/SR1154 silver
oxide cells come in the same package. They have about 50% more
capacity and a much flatter discharge curve. Some of the cheapo
calipers crap out below about 1.4V. The alkaline battery has plenty
of capacity left at 1.4V, but the caliper doesn't want to run. If
your caliper cames with a silver-oxide cell, it should probably use
silver oxide batteries. If it came with alkaline and has a short
battery life, it might be worthwhile trying silver-oxide. If you're
ambitious, it might be useful to run the caliper off a bench power
supply and check how low a voltage will work.

[Spehro Pefhany]

Be sure to check how high a voltage too, and report back. ;-)



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

[dagmarg...@yahoo.com]

On Nov 20, 8:45 pm, Jeff Liebermann <je...@cruzio.com> wrote:

> On Sun, 20 Nov 2011 16:47:25 -0800 (PST), "Ron D." wrote:

> >I have a cheap Caliper too and it recently went flakey.
>
> >I did my standard trick:  Remove battery.  Short battery contacts:
> >Insert new battery.  Worked.
>
> My cheap electronic caliper goes nuts when I transmit on UHF anywhere
> near it.  However, it doesn't require the battery removal ordeal to
> recover.  I just reset to zero and continue.
>
> >Mine uses an LR44 and you HAVE TO use an LR44, not a substitute
> >battery that you can get a Radio Shack.
> >Mechanically they are not the same.
>
> I beg to differ.  The general package name is LR44 in an 11.6mm dia x
> 5.4mm thick package alkaline cell.  There are slight variations, but
> the IEC LR1154 equivalents (LR44/LR154, A76, 157/303/357) are all the
> same size.  Where you can have problems is that the SR44/SR1154 silver
> oxide cells come in the same package.  They have about 50% more
> capacity and a much flatter discharge curve.  Some of the cheapo
> calipers crap out below about 1.4V.  The alkaline battery has plenty
> of capacity left at 1.4V, but the caliper doesn't want to run.  If
> your caliper cames with a silver-oxide cell, it should probably use
> silver oxide batteries.  If it came with alkaline and has a short
> battery life, it might be worthwhile trying silver-oxide.  If you're
> ambitious, it might be useful to run the caliper off a bench power
> supply and check how low a voltage will work.

I just measured a Harbor Freight (Chinese) 8-incher.

Drain: 13.5uA (off), 14.5uA (on)
Battery low threshold (blinking display): 1.37V
Lowest operating voltage: 1.01V

So, it's clearly made for silver-oxide cells. The battery low
threshold is set appropriately for a silver oxide cell (e.g. SR-44).

It's a lousy threshold for using alkalines--they're barely broken in
at that voltage.

14.5uA means a year from a silver oxide cell--that's not horrible.

--
Cheers,
James Arthur

[dagmarg...@yahoo.com]

You can get the silver oxide cells occasionally from Big Lots, a card
of 5 goes for something like $2.50. Other than that, drugstores have
'em for something like $3-5, per cell (!).

And yes, they're mechanically the same.

--
Cheers,
James Arthur

[Martin Riddle]

<dagmarg...@yahoo.com> wrote in message
news:07d0ac35-1cf3-4ed1...@p2g2000vbj.googlegroups.com...

Why bother including an on off switch?

Cheers

[DoN. Nichols]

On 2011-11-20, amdx <am...@knologynotthis.net> wrote:

> On 11/19/2011 9:01 PM, P E Schoen wrote:
>> I have two Harbor Freight digital calipers, item #47257, and I've had
>> problems with one of them especially, where the display will go blank.
>> It seemed to work sometimes if I squeezed the enclosure, and I thought
>> it was a bad battery or bad connection. But a fresh battery didn't work.
>>
>

> That's why I like the Dial calipers vs Digital Calipers, no concern
> about batteries or electronics.

But -- dial calipers are vulnerable to two problems.

1) Drop or bump them and the pinion will disengage from the
rack and shift to give a wrong reading. You can work around
that by rotating the dial to re-zero it, but past a certain
point, it gets to be awkward to read.

2) Small chips can get engaged in the rack and the zero point
will shift every time you pass that point.

Vernier calipers don't have these problems, but are more
difficult to read with aging eyes and poor light.

Yes -- there are ways to fix both, but a lot more fiddly than
fixing an exhausted battery on the digital calipers.

And the digital calipers have two other advantages over dial and
Vernier calipers:

a) Switch between metric and inch modes at the push of a button,
even converting readings already locked in. (Actually, some
Vernier calipers have both scales, so this does not apply.)

b) Ability to reset the zero where-ever you want, so you can set
it to zero on a target dimension, and then read how much you
need to machine off in a lathe to see how many passes before
you are close enough to do serious measurements. You can even
keep a calculator handy to divide by two depending on whether
your cross-feed dial reads in diameter or radius.

c) (O.K. Three for some people. :-) -- the ability to transfer the
measurement to a computer (without typing errors) for statistics
or other similar processing.

> (Dial Calipers, Item # 66541, Out of Stock)
>
> Although a couple years ago HF had the 6" Digital calipers on sale for
> $9.99, I bought two. They are still in the boxes and I use my Dial
> calipers. I think I might give one away as a Christmas present.

I have three 6" (150 mm) digital calipers, and a 12" (300 mm)
digital caliper. (Not counting two old B&S 6" ones which require
mercury cells for power, which are made of unobtanium.)

I also have a two dial calipers -- a 6" Phase-II, and a 150 mm
Starrett.

And two Vernier calipers -- a 6"/150mm and a 24" (I forget
whether that one has metric units as well.)

However -- the ones which I reach for most of the time are the
digital ones -- because of the memory feature and the ability to switch
measurement systems to match what I am working on and with.

One 6" digital stays near the main lathe (12x24" Clausing) and
one near the little CNC lathe in the opposite corner of the shop. The
cheapest digital ($18.00 at a hamfest) lives up here by the computer for
when I want to measure something quickly.

I keep a spare cell (or set as appropriate) in the case of each
digital, so I am not out of operation for very long if the cells in the
caliper go bad.

The dial or the Vernier get used when I expect to be away from
batteries for a while -- or in case the production of batteries ceases
thanks to some apocalypse. :-) (Or the 24" one for when I need to
measure beyond the range of the 12" digital.)

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: <BPdnic...@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

[DoN. Nichols]

On 2011-11-20, N_Cook <div...@tcp.co.uk> wrote:
> amdx <am...@knologynotthis.net> wrote in message
> news:4756b$4ec8f55d$18ec6dd7$12...@KNOLOGY.NET...

>> On 11/19/2011 9:01 PM, P E Schoen wrote:
>> > I have two Harbor Freight digital calipers, item #47257, and I've had
>> > problems with one of them especially, where the display will go blank.
>> > It seemed to work sometimes if I squeezed the enclosure, and I thought
>> > it was a bad battery or bad connection. But a fresh battery didn't work.
>> >
>>
>> That's why I like the Dial calipers vs Digital Calipers, no concern
>> about batteries or electronics.

>> (Dial Calipers, Item # 66541, Out of Stock)
>>
>> Although a couple years ago HF had the 6" Digital calipers on sale for
>> $9.99, I bought two. They are still in the boxes and I use my Dial
>> calipers. I think I might give one away as a Christmas present.

>> Mikek

>
>
>
> I've never used the new-fangled ones - do you have to do a clean jaws, close
> jaws, zero calibration check/0 reset ,every time you use them ? as the count
> must be lost each time it is switched off

Most of the newer ones dont really switch off -- just the
display is blanked to save power, so the reading is preserved. (But,
the battery life is not as good. On the Starrett ones which I have, the
battery holder slides in and out, and by sliding it less than 1/16" you
can disconnect the battery (thus extending the life) at the cost of
having to re-zero when you power them back on. I normally do exactly
this.

The Mitutoyo is not as convenient to disconnect the batteries,
so I live with it -- but it also has an extra feature. Aside from
remembering when turned off -- it can remember two zeros -- the absolute
zero, and the incremental zero (say you zero it to tell how much left to
remove in the lathe), and by pushing a button, you go back to the
absolute zero without having to clean the jaws and check.

[DoN. Nichols]

On 2011-11-20, Jamie <jamie_ka1lpa_not_v...@charter.net> wrote:
> N_Cook wrote:
>
>> <sta...@prolynx.com> wrote in message
>> news:0156c7a7-8bb2-4f32...@u6g2000vbg.googlegroups.com...

[ ... ]

>>>I've never used the new-fangled ones - do you have to do a clean jaws,
>>
>> close
>>
>>>jaws, zero calibration check/0 reset ,every time you use them ? as the
>>
>> count
>>
>>>must be lost each time it is switched off
>>
>>
>> Used to be, they've improved things. On at least some, the count is
>> kept live and just the display is switched off. It all goes away when
>> batteries are switched, but that can be lived with.
>>
>> Stan
>>
>> +++
>>
>> So that explains , down thread, the drawback of dying batteries when
>> switched "off"
>>
>>
> I have the HF digital calipers and I need to pull the battery when not
> in use other wise, it'll be dead next time I need it. It seems to drain
> quite fast.

How fast it dies is in part a function of the quality of the
batteries used. There are two series, "44" and "357" which are
interchangeable (and both magnum handgun calipers, FWIW) which can be
either Alkaline cells, or Silver Oxide cells. The Silver Oxide (usually
a "SR" prefix to the number) gives *much* better life -- at a
significantly higher cost. However, those more expensive ones are the
ones which I tend to use. The same in the digital micrometers, which
read down to 0.00005" or 0.001 mm.

> Other than that, it seems to work very nicely..

They are nice to have -- and typically the more expensive ones
*do* work better.

[DoN. Nichols]

Or different quality of battery as I just posted above. :-)

[dagmarg...@yahoo.com]

On Nov 20, 9:55 pm, "Martin Riddle" <martin_...@verizon.net> wrote:
> <dagmargoodb...@yahoo.com> wrote in message

> Why bother including an on off switch?

It's really not worth it for 1uA.

If I designed these, I'd shoot for 2uA active draw, like the
Mitutoyos, and set the battery low threshold at 1.1V (for alkalines).
The battery consumption is the biggest fault with these. Apart from
that, they're impressive.

I sometimes think about wiring up a "AAA" or solar cell and just
forgetting it, but for $0.50 a year it's not worth the trouble.

--
Cheers,
James Arthur

[Jeff Liebermann]

On Sun, 20 Nov 2011 19:57:32 -0500, Rich Webb
<bbe...@mapson.nozirev.ten> wrote:

>I tried a paste of cream of tartar from the spice rack in the kitchen on
>the battery terminals on a long forgotten remote control that had spewed
>its battery guts to make a nasty, green mess of the copper-nickel
>strips. Worked amazingly well, better than anything else I've tried for
>that particular problem. YMMV, of course.

Cream of tartar is potassium bitartrate. Mix the powder with some
white vinegar or any weak acid and you get a paste that can be used as
a cleaner:
<http://www.ehow.com/how_5758669_clean-vinegar-cream-tartar.html>

For cleaning up the green slime left after a battery exceeds its
warranty, I use ammonia cleaner. I also like the foam it produces.
Copper (cupric) oxide is soluble in ammonium hydroxide, but not in
water.

[DoN. Nichols]

On 2011-11-20, N_Cook <div...@tcp.co.uk> wrote:

> Dave Plumpe <last...@mindspring.com> wrote in message
> news:dcCdnbxH1tldnVTT...@earthlink.com...

>> Not only do they remember where Zero is, they even keep track of any
>> movement that occurs while they're turned off. Smart little devils.
>>
>> I find myself more & more reaching for the digital ones for the ease of
>> swapping between inches & millimeters.

[ ... ]

>> "N_Cook" <div...@tcp.co.uk> wrote in message
>> news:jaatmo$4n4$1...@dont-email.me...

>> >
>> > I've never used the new-fangled ones - do you have to do a clean jaws,
>> > close
>> > jaws, zero calibration check/0 reset ,every time you use them ? as the
>> > count
>> > must be lost each time it is switched off
>> >
>>
>>
>

> An engineer told me never close the jaws of a micrometer or vernier calipers
> for storage, leave the jaws open slightly.

A micrometer should never be stored closed. (Thermal changes in
dimensions can stress the components and reduce accuracy. Vernier
calipers should not have a problem as long as you don't *lock* them
closed -- either with the slide or the fine adjust slide.

> Do these digitally things require

> the jaws closing before switching off ? How do they know of any movement of

> the jaws when switched off elsewise?

Most modern digital calipers only shut off the display, and keep
the counters and sensors powered up, so they can know where they are
when the display is switched back on -- and some will even switch the
display back on when it senses motion above some minimum value.

[gregz]

Yes, some old navy guy contacted me and I stuck it in there. Have not
updated anything for a while.

Greg szekeres

[DoN. Nichols]

On 2011-11-20, Jeff Liebermann <je...@cruzio.com> wrote:

> On Sun, 20 Nov 2011 13:38:36 -0000, "N_Cook" <div...@tcp.co.uk>
> wrote:
>>An engineer told me never close the jaws of a micrometer or vernier calipers
>>for storage, leave the jaws open slightly.
>

> True. With gear type calipers, the lubricating grease tends to
> migrate to that position. If a sufficiently filthy environment, an
> lump of dirt encrusted grease will be left in that position. If it
> happens to be at 0.0, then it will be difficult to accurately
> calibrate the mechanism.

But he said "Vernier calipers" which have no such mechanism.
Though people tend to lock the slides, so thermal stress distortion
could be a problem with them stored closed and locked.

> There are also some minor reasons, such as
> the tendency for two parallel surfaces to trap moisture between them
> and rust.

Assuming non stainless steel jaws. (I've never seen calipers
with carbide faced jaws, unlike good micrometers.)

[ ... ]

>>How do they know of any movement of
>>the jaws when switched off elsewise?
>

> Only the display is turned off. The pulse counting mechanism is still
> operating and functional. The downside is that the battery will be
> dead in about 6-9 months. Most include a spare LR44 battery. I had
> to buy a pile of them to keep my calipers going. Somehow, the battery
> is usually dead when I need to use them.
>
> 50 batteries for $3.75
><http://www.ebay.com/itm/220751739681>

There is your problem -- cheap cells. Don't use the LR44 (those
are alkaline batteries), use the SR44 and SR357 (Silver Oxide cells,
with much longer life). Then things will probably last at least six
months in storage. The SR44 and SR357 are pretty much interchangeable.
I don't even know why there are the two series -- though you will often
find them with both designators marked on the same cell or packaging. :-)

> I have an expensive set of Starett calipers (both metric and US). I
> use them more often than the electronic variety, mostly out of habit.
> My most useful measuring tools are my 6" pocket steel scale and a tape
> measure.

While I tend to use the digital calipers by preference. Half as
many calipers needed to cover the metric and inch measurements.

[gregz]

I bought some oleic acid from bill. I tried diluting it with isopropyl
alcohol, seems to mix well.

My old cans of spray of Contaclean got all sticky and the metal was looking
bad where it contacted the fluid build up. I think it also gummed up pots.
Contaclean is Cramolins replacement for cramolin. I'm not trying to order
it anymore because it costs watt too much to ship into the states.
Interesting though, my old vial of cramolin never gummed up on the injector
tube. The can of Contaclean clearly states to remove before operating, with
a cleaner. Gummy!!
I can't remember if I dried pure oleic acid to test for gumminess. Probably
does.
Deoxit does not gum. Never tried to dry up pure red caig in the vial
injector.
Deoxit is only 5% concentration in the spray.

Greg

[DoN. Nichols]

I've ignored the "Followup-To: " header, because I believe that this
also belongs in at least rec.crafts.metalworking, where I am following
it, and I would miss my own followup and any responses if it were kept
to a single group as requested.

On 2011-11-20, Fred Abse <excret...@invalid.invalid> wrote:

> On Sun, 20 Nov 2011 06:41:03 -0600, amdx wrote:
>
>> That's why I like the Dial calipers vs Digital Calipers, no concern
>> about batteries or electronics.
>

> I prefer a "proper" vernier. At least you can verify those by eye.

Depends on how old the eye is and how good the illumination is.

> I never
> did trust digital calipers to hold their zero and not skip under workshop
> conditions, Half a lifetime dealing with incremental encoders has made me
> wary.

The old B&S ones, which used glass encoders in the slot where
the rack gear would otherwise be were sensitive to coolant in the slot.
But the modern units seem to be quite good at not skipping.

> I *might* trust a Mitutoyo digital caliper or height gage in inspection
> room conditions.

I trust them (as much as a caliper *can* be trusted compared to
a micrometer) in shop conditions as well.

> Dial calipers have all sorts of racks and gears to go sloppy.

Agreed -- or to pick up bits of swarf and skip.

> I suppose nobody under fifty knows how to read a real vernier, or a slide
> rule for that matter ;-(

I know how to use both -- but then I am (well) over fifty. :-)

But there have been verniers on the thimbles of the better
micrometers much more recently than that, so presumably some of the
younger crowd know.

[Jeff Liebermann]

On Mon, 21 Nov 2011 03:33:20 +0000 (UTC), gregz <ze...@comcast.net>

Oh, those are your pages. Nice info and thanks.

The silicone and salt atmosphere problem is real. It forms sodium
silicate, which is water soluable. Add almost any acid, and you get
silicic acid. Heat and dry that you get silica gel, which is quite
hard and not very soluable in anything. It takes a while, but it does
happen.

I used to work for a marine radio manufactory in the 1970's. Customers
would sometimes use various lubricants loaded with silicone to clean
pots and switches. It would work, but about a year later, we would
get the radios back with seriously intermittent pots and switches. No
amount of solvent cleaning would fix them, so we just replaced them.
We just assumed they were internally corroded or salt encrusted. I
didn't discover the silicone and salt atmosphere problem until many
years later (when I repeated the mistake on a consulting project).

[Jeff Liebermann]

On Mon, 21 Nov 2011 03:57:48 +0000 (UTC), gregz <ze...@comcast.net>
wrote:

>I bought some oleic acid from bill. I tried diluting it with isopropyl
>alcohol, seems to mix well.

Olive oil works almost as well. It's about 50% oleic acid. My
solution is mostly Coleman fuel (naphtha), some olive oil, and a
little alcohol. It works and leaves the radio smelling "organic".

>My old cans of spray of Contaclean got all sticky and the metal was looking
>bad where it contacted the fluid build up. I think it also gummed up pots.

Well yes. Such cleaners (and Cramolin) are mostly mineral oil. Remove
the volatiles and antioxidants, and what's left is mineral oil. There
are different types of mineral oils: paraffin, naphtha, various
petroleum distillates, and mixtures. The paraffin residue left after
evaporation might be the gum that you're seeing.

>Contaclean is Cramolins replacement for cramolin. I'm not trying to order
>it anymore because it costs watt too much to ship into the states.

It appears that Contaclean is the same as the old Cramolin Red
(R-100). Mostly mineral oil (hexane) and isopropyl alcohol. MSDS:
<http://www.farnell.com/datasheets/1493224.pdf>
Hmmm... looks like the oleic acid was removed.

>Interesting though, my old vial of cramolin never gummed up on the injector
>tube. The can of Contaclean clearly states to remove before operating, with
>a cleaner. Gummy!!
>I can't remember if I dried pure oleic acid to test for gumminess. Probably
>does.

I would blame the mineral oil instead, especially since there doesn't
seem to be any oleic acid in the Contaclean reformulation. Oleic acid
is much like corn oil or olive oil. It will leave a gummy residue
under the correct conditions. However, there is only 5% oleic acid in
the bottle, which isn't enough to leave much residue. If there's
plenty of residue, it's probably the mineral oil.

>Deoxit does not gum. Never tried to dry up pure red caig in the vial
>injector.
>Deoxit is only 5% concentration in the spray.
>
>Greg

[Jeff Liebermann]

On Sun, 20 Nov 2011 22:41:49 -0800, Jeff Liebermann <je...@cruzio.com>
wrote:

>It appears that Contaclean is the same as the old Cramolin Red
>(R-100). Mostly mineral oil (hexane) and isopropyl alcohol. MSDS:
><http://www.farnell.com/datasheets/1493224.pdf>
>Hmmm... looks like the oleic acid was removed.

Oops. It's still there, but well hidden. It's listed as an
"aliphatic hydrocarbon", which includes fatty acids such as oleic
acid.

[Gunner Asch]

On 21 Nov 2011 03:24:37 GMT, "DoN. Nichols" <BPdnic...@d-and-d.com>
wrote:

>On 2011-11-20, Bob Engelhardt <bobeng...@comcast.net> wrote:
>> Jamie wrote:
>>> I have the HF digital calipers and I need to pull the battery when not
>>> in use other wise, it'll be dead next time I need it. It seems to drain
>>> quite fast.
>> ...
>>
>> I have one & the battery lasts quite a while (doesn't get used much).
>> Maybe a different model. Or a different batch. Or different spots on
>> the quality curve <G>.
>
> Or different quality of battery as I just posted above. :-)
>
> Enjoy,
> DoN.

Many 99c stores sell a flatpack of 5-10 standard 357 batteries for a
dollar.

So I use 2 batteries a year. Or even 3. Im still way ahead of the curve
when SR44s are $3 each

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

[N_Cook]

Spehro Pefhany <spef...@interlogDOTyou.knowwhat> wrote in message
news:2ddjc7tt4m10a6q7k...@4ax.com...

If I had one of these I'd fit onto the calipers a small solar cell and diode
to trickle charge the original battery ie not specifically rechargeable ,
and replace the lid of its casing with a glass panel and leave on a bright
position .

[J.B. Wood]

On 11/19/2011 11:19 PM, Jim Yanik wrote:

> use Boeing Boeshield T-9 to prevent the rusting of your tools.

>
> I wonder if Cramolin/DeOxit would work on the conductive strip?
>

Hello, and DeoxIT is the best thing I've ever come across for cleaning
and de-oxidizing electrical contacts. It also does wonders with
scratchy volume and tone pots and it'll be long while before you have to
apply it again. Sincerely,


--
J. B. Wood e-mail: arl_1...@hotmail.com

[William Sommerwerck]

> I never have been able to get much visible effect of so called corrosion

> removers. Oleic acid probably being best, but supposedly the Cramolin

> chemist also had input on making deoxit. On a short term test I can
visibly
> wipe off oxide with an alcohol swipe, being just as effective. Most of the
> removing is mechanical in nature, and any liquid helps.

I'm inclined to disagree. Cramolin/DeOxit definitely work on tin- and
nickel-plated surfaces. They are not as effective on gold-plated surfaces;
ProGold does a better job. It isn't just a matter of mild abrasion; a
chemical reaction of some sort is needed.

[Jim Yanik]

Jeff Liebermann <je...@cruzio.com> wrote in
news:ff9jc7h30fqjm073j...@4ax.com:

> Homebrew cleaners and protectors:
><http://www.pitt.edu/~szekeres/cleaner.htm>
> The comments on the effects of silicones plus salt in WD40 are
> interesting.
>

WD-40 is mostly kerosene.

--
Jim Yanik
jyanik
at
localnet
dot com

[Jeff Liebermann]

On Mon, 21 Nov 2011 10:36:03 -0600, Jim Yanik <jya...@abuse.gov>
wrote:

>Jeff Liebermann <je...@cruzio.com> wrote in
>news:ff9jc7h30fqjm073j...@4ax.com:
>
>
>> Homebrew cleaners and protectors:
>><http://www.pitt.edu/~szekeres/cleaner.htm>
>> The comments on the effects of silicones plus salt in WD40 are
>> interesting.
>>
>
>WD-40 is mostly kerosene.

Close. It's mostly Stoddard Solvent, also known as mineral spirits.
<http://www.snopes.com/inboxer/household/wd-40.asp>
<http://en.wikipedia.org/wiki/WD-40>
<http://en.wikipedia.org/wiki/Stoddard_solvent>
50% Stoddard solvent (i.e., mineral spirits: primarily hexane,
somewhat similar to kerosene)
25% Liquefied petroleum gas (presumably as a propellant; carbon
dioxide is now used instead to reduce WD-40's considerable
flammability)
15+% Mineral oil (light lubricating oil)
10-% Inert ingredients

Reverse engineering at its best:
<http://www.wired.com/science/discoveries/magazine/17-05/st_whatsinside>

USA MSDS sheet:
<http://www.wd40company.com/files/pdf/msds-wd494716385.pdf>

The key ingredient is a sulfactant (wetting agent), to reduce surface
tension and make it "cling" to objects and "puddle" water. My
guess(tm) the reason it took 40 trys is that they had a difficult time
finding one that would work in a solvent solution.

[Ron D.]

Th 357 and the LR44 ARE NOT quite the same in experience, The LR44
seems to have a slightly domed top and it seems to make a difference
in all of my products that use them. I can't find evident to support
my claim, but experience, unfortunately.

In general, the LF357's fit a little looser in the holder and the
LF44's are easier to insert.

[gregz]

Good info. Darn, I liked to use the can as a flame thrower to kill pests
with the flammable propellant. Bags worms met their doom.

Greg

[P E Schoen]

"Gunner Asch" wrote in message
news:aa0kc750e2tsad302...@4ax.com...

> Many 99c stores sell a flatpack of 5-10 standard 357 batteries
> for a dollar.

I'm not sure I'd trust them in something any more expensive than a
flashlight. I have seen them corrode and leak. And the only thing the 99
cent store might be willing to do is give you another pack or refund your

dollar.

> So I use 2 batteries a year. Or even 3. Im still way ahead of the
> curve when SR44s are $3 each

I just purchased four genuine SR44s from an eBay store, for $3, including
first class mail shipping. The same company also has larger packs for quite
a bit less.
http://stores.ebay.com/RL-batterydepot?_trksid=p4340.l2563

I also measured the current draw on my calipers, and it's about 12.5 uA
either on or off. It seems to spike a bit when turned on. (So do I :)

They are specified at about 175 mAhr, according to http://www.sr44.com/, so
lifetime should be about 14000 hrs or 1.5 years, but the spec is for a low
voltage of 1.3V, which is probably below the limit of the electronics in the
caliper, at least for the low battery indicator.

Here is a handy list of the various sizes with different chemistry and their
mA-hr capacities: http://en.wikipedia.org/wiki/List_of_battery_sizes

Paul
www.pstech-inc.com

[amdx]

Harbor Freight Has the 6" dial Caliper on sale 11/24

http://www.harborfreight.com/preview-thanksgiving.html?utm_medium=email&utm_campaign=4711a&utm_source=1003

Mikek

[Jamie]

Nice, I like the metal cutting saw they have there just off to the right..

Think I'll do a stop in for that.

Jamie

[amdx]

Do note, it is pneumatic.
Fine if your setup for it.
Mikek

[DoN. Nichols]

On 2011-11-21, Martin Riddle <marti...@verizon.net> wrote:
>
><dagmarg...@yahoo.com> wrote in message
> news:07d0ac35-1cf3-4ed1...@p2g2000vbj.googlegroups.com...
>> On Nov 20, 8:45 pm, Jeff Liebermann <je...@cruzio.com> wrote:

>>> On Sun, 20 Nov 2011 16:47:25 -0800 (PST), "Ron D." wrote:
>>
>>> >I have a cheap Caliper too and it recently went flakey.

[ ... ]

>>> same size. Where you can have problems is that the SR44/SR1154
>>> silver
>>> oxide cells come in the same package. They have about 50% more
>>> capacity and a much flatter discharge curve. Some of the cheapo
>>> calipers crap out below about 1.4V. The alkaline battery has plenty
>>> of capacity left at 1.4V, but the caliper doesn't want to run. If
>>> your caliper cames with a silver-oxide cell, it should probably use
>>> silver oxide batteries. If it came with alkaline and has a short
>>> battery life, it might be worthwhile trying silver-oxide. If you're
>>> ambitious, it might be useful to run the caliper off a bench power
>>> supply and check how low a voltage will work.
>>

>> I just measured a Harbor Freight (Chinese) 8-incher.
>>
>> Drain: 13.5uA (off), 14.5uA (on)
>> Battery low threshold (blinking display): 1.37V
>> Lowest operating voltage: 1.01V
>>
>> So, it's clearly made for silver-oxide cells. The battery low
>> threshold is set appropriately for a silver oxide cell (e.g. SR-44).
>>
>> It's a lousy threshold for using alkalines--they're barely broken in
>> at that voltage.
>>
>> 14.5uA means a year from a silver oxide cell--that's not horrible.

[ ... ]

> Why bother including an on off switch?

It is an off switch to turn the *display* (only) back on. They
sometimes make it also turn the display back off to make people feel
better. :-)

The auto-turn-off time of the display is usually good enough.

[DoN. Nichols]

On 2011-11-21, dagmarg...@yahoo.com <dagmarg...@yahoo.com> wrote:
> On Nov 20, 9:55 pm, "Martin Riddle" <martin_...@verizon.net> wrote:
>> <dagmargoodb...@yahoo.com> wrote in message
>>
>> news:07d0ac35-1cf3-4ed1...@p2g2000vbj.googlegroups.com...
>>
>>
>>

>> > I just measured a Harbor Freight (Chinese) 8-incher.
>>
>> > Drain: 13.5uA (off), 14.5uA (on)
>> > Battery low threshold (blinking display): 1.37V
>> > Lowest operating voltage: 1.01V

[ ... ]

>> Why bother including an on off switch?
>
> It's really not worth it for 1uA.
>
> If I designed these, I'd shoot for 2uA active draw, like the
> Mitutoyos, and set the battery low threshold at 1.1V (for alkalines).
> The battery consumption is the biggest fault with these. Apart from
> that, they're impressive.
>
> I sometimes think about wiring up a "AAA" or solar cell and just
> forgetting it, but for $0.50 a year it's not worth the trouble.

Actually -- there *are* some "solar powered" ones -- by Mitutoyo
IIRC. They would probably be excellent used daily in a well-illuminated
shop. In my shop, often dark for days at a time, until a project lures
me there, the replaceable batteries are a better choice.

I did recently get an auto-darkening welding hood from Harbor
Freight which is solar powered, and based on what I have read about them
dying if not used regularly, I've put mine on a folding workstool facing
out the window so it sees daylight to maintain the charge. I'll proably
eventually have to perform surgery and replace the rechargeable cells in
there. There is a temptation to provide a connection for an AC-powered
trickle charger so I can store it more conveniently. What would be
particularly nice would be an induction coupled charger like those for
electric toothbrushes. Just put it on a stand and expect it to be fully
charged when I come back.

If the charge is good enough to work on the first strike, it
should work fine for the rest of the day, because it will be getting a
charge boost from the arc -- close enough to vigorous sunlight. :-)

[DoN. Nichols]

On 2011-11-22, P E Schoen <pa...@pstech-inc.com> wrote:
> "Gunner Asch" wrote in message
> news:aa0kc750e2tsad302...@4ax.com...
>
>> Many 99c stores sell a flatpack of 5-10 standard 357 batteries
>> for a dollar.
>
> I'm not sure I'd trust them in something any more expensive than a
> flashlight.

Well ... I've paid more for *some* flashlights (typically
multi-LED ones) than for *some* digital calipers (import from a
hamfest), so it is a toss-up there. :-)

> I have seen them corrode and leak. And the only thing the 99
> cent store might be willing to do is give you another pack or refund your
> dollar.

If you are going to leave the calipers for more than a week,
pull the cell(s) and store them separately -- perhaps in a small zip-loc
baggie, so they don't damage anything else when leaking.

FWIW I've not seen the Silver Oxide ("SR" prefix) ones leak in anything
in which I have used them.

[dagmarg...@yahoo.com]

On Nov 21, 9:08 pm, "DoN. Nichols" <BPdnichol...@d-and-d.com> wrote:

> On 2011-11-21, dagmargoodb...@yahoo.com <dagmargoodb...@yahoo.com> wrote:
>
> > On Nov 20, 9:55 pm, "Martin Riddle" <martin_...@verizon.net> wrote:
> >> <dagmargoodb...@yahoo.com> wrote in message
>
> >>news:07d0ac35-1cf3-4ed1...@p2g2000vbj.googlegroups.com...
>
> >> > I just measured a Harbor Freight (Chinese) 8-incher.
>
> >> > Drain: 13.5uA (off), 14.5uA (on)
> >> > Battery low threshold (blinking display): 1.37V
> >> > Lowest operating voltage: 1.01V
>
>         [ ... ]
>
> >> Why bother including an on off switch?
>
> > It's really not worth it for 1uA.
>
> > If I designed these, I'd shoot for 2uA active draw, like the
> > Mitutoyos, and set the battery low threshold at 1.1V (for alkalines).
> > The battery consumption is the biggest fault with these.  Apart from
> > that, they're impressive.
>
> > I sometimes think about wiring up a "AAA" or solar cell and just
> > forgetting it, but for $0.50 a year it's not worth the trouble.
>
>         Actually -- there *are* some "solar powered" ones -- by Mitutoyo
> IIRC.  They would probably be excellent used daily in a well-illuminated
> shop.

I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
resisted. Something about having a glass window on a machine tool
close to all that hard steel just didn't sit well--it brought up
memories of scratched and broken watch crystals.

OTOH, I paid $10 for most of my HF calipers. Those you can take
chances with. Using the 8x25mm solar panel from a $1 calculator, a
super capacitor for storage, and an LED as a regulator diode was my
notion. $2 in parts, $500 labor ;-).

I fitted one to the lathe carriage--best thing I ever did.
Removable. I fitted another to the tailstock ram. With it you can
bore to 0.002" depth every time without even trying. Magic.

>  In my shop, often dark for days at a time, until a project lures
> me there, the replaceable batteries are a better choice.
>
>         I did recently get an auto-darkening welding hood from Harbor
> Freight which is solar powered, and based on what I have read about them
> dying if not used regularly, I've put mine on a folding workstool facing
> out the window so it sees daylight to maintain the charge.  I'll proably
> eventually have to perform surgery and replace the rechargeable cells in
> there.  There is a temptation to provide a connection for an AC-powered
> trickle charger so I can store it more conveniently.  What would be
> particularly nice would be an induction coupled charger like those for
> electric toothbrushes.  Just put it on a stand and expect it to be fully
> charged when I come back.
>
>         If the charge is good enough to work on the first strike, it
> should work fine for the rest of the day, because it will be getting a
> charge boost from the arc -- close enough to vigorous sunlight. :-)

Sounds like a LiIon cell. If so, those can't be allowed to go dead,
as you've surmised.

--
Cheers,
James Arthur

[P E Schoen]

"DoN. Nichols" wrote in message
news:slrnjclve8.op...@Katana.d-and-d.com...

> On 2011-11-21, Martin Riddle <marti...@verizon.net> wrote:

>> Why bother including an on off switch?

> It is an off switch to turn the *display* (only) back on. They
> sometimes make it also turn the display back off to make
> people feel better. :-)

> The auto-turn-off time of the display is usually good enough.

Still, there's no benefit to turning off the display, in this case. Might
just as well have it display "OFF".

I bought a high-end headlamp from Coleman a few years ago
http://www.coleman.com/coleman/ColemanCom/detail.asp?CategoryID=1116&product_id=2000000265#
and every time I went to use it the batteries (4 AA) were dead. I measured
the current draw when turned off, and it was something like 300 uA, which
should have provided 8000 hours (almost one year) for the 2500 mA-hr
batteries. But I was getting only a few weeks before finding them exhausted.
Maybe the current increased as the battery voltage dropped. I usually used
rechargeable NiMH and they might have been old and tired. But, still, there
is no reason for 300 uA standby current on a flashlight. Even if it had a
microcontroller, a typical PIC18F2420 draws only 11 uA while running, and
only 100 nanoamps in sleep mode! So, I just pop out one of the batteries
while I'm not using it. There's no easy place to install a switch.

Paul
www.muttleydog.com

[P E Schoen]

"DoN. Nichols" wrote in message

news:slrnjcm1ee.op...@Katana.d-and-d.com...

> Well ... I've paid more for *some* flashlights (typically
> multi-LED ones) than for *some* digital calipers (import
> from a hamfest), so it is a toss-up there. :-)

Yes, the Coleman headlamp I mentioned elsewhere lists for $50, and I paid
probably $20 on clearance, so I agree, in that case. But most flashlights
with coin cells are pretty much disposable.

> If you are going to leave the calipers for more than a week,
> pull the cell(s) and store them separately -- perhaps in a small
> zip-loc baggie, so they don't damage anything else when leaking.

That's what I am going to do. There is a cutout in the foam of the caliper
case for a spare. I also put the other three cells in their original
packaging in there. I plan to use the calipers more now that I can depend on
them (and know how to fix them). Usually I don't do much precision
machining, and I have a cheap plastic dial caliper that is good to about
0.01" and is immune to humidity and most abuse.

> FWIW I've not seen the Silver Oxide ("SR" prefix) ones leak in
> anything in which I have used them.

I think the original cell in the HF caliper was actually alkaline, and
fortunately I had removed it (but kept in the case) when I had tried to fix
them a few years ago with no joy. When I opened it recently, the cell was
rusty and there was some liquid that had oozed out. I've also had some NiMH
AA cells that leaked. But probably the silver cells are better made and the
chemicals may be less aggressive. Now that I've found an on-line source with
good pricing I think I'll stick with them, although it's tempting to get the
Chinese copies for 10 cents each.

Paul

[dagmarg...@yahoo.com]

On Nov 21, 9:34 pm, "P E Schoen" <p...@pstech-inc.com> wrote:
> "DoN. Nichols"  wrote in message
>
> news:slrnjclve8.op...@Katana.d-and-d.com...
>

> > On 2011-11-21, Martin Riddle <martin_...@verizon.net> wrote:
> >> Why bother including an on off switch?
> > It is an off switch to turn the *display* (only) back on.  They
> > sometimes make it also turn the display back off to make
> > people feel better. :-)
> > The auto-turn-off time of the display is usually good enough.
>
> Still, there's no benefit to turning off the display, in this case. Might
> just as well have it display "OFF".
>

> I bought a high-end headlamp from Coleman a few years agohttp://www.coleman.com/coleman/ColemanCom/detail.asp?CategoryID=1116&...

> and every time I went to use it the batteries (4 AA) were dead. I measured
> the current draw when turned off, and it was something like 300 uA, which
> should have provided 8000 hours (almost one year) for the 2500 mA-hr
> batteries. But I was getting only a few weeks before finding them exhausted.
> Maybe the current increased as the battery voltage dropped. I usually used
> rechargeable NiMH and they might have been old and tired. But, still, there
> is no reason for 300 uA standby current on a flashlight. Even if it had a
> microcontroller, a typical PIC18F2420 draws only 11 uA while running, and
> only 100 nanoamps in sleep mode! So, I just pop out one of the batteries
> while I'm not using it. There's no easy place to install a switch.
>
> Paulwww.muttleydog.com

I measured some ordinary NiMH cells' self-discharge, 1,600mAH, @ 1.6mA
IIRC. The high-capacity rechargeables are wickedly worse. I've got
one set that won't hold a charge much over two weeks, no kidding,
even brand-new. Self-discharge current on the order of 5-7mA.

There are low-self-discharge NiMH that hold a charge much longer,
sometimes up to a year. Highly recommended. Ray-O-Vac Hybrids, Sanyo
Eneloop, and Duracell has some too.

--
Cheers,
James Arthur

[Gunner Asch]

On Mon, 21 Nov 2011 19:32:51 -0500, "P E Schoen" <pa...@pstech-inc.com>
wrote:

>

>I just purchased four genuine SR44s from an eBay store, for $3, including
>first class mail shipping. The same company also has larger packs for quite
>a bit less.
>http://stores.ebay.com/RL-batterydepot?_trksid=p4340.l2563

Thanks!!!

Ill check em out and stock up!!

[Michael A. Terrell]

P E Schoen wrote:
>
> I've also had some NiMH AA cells that leaked.

I have the control panel & 'Rabbit Semiconductor' RCM2000 computer
board from an Ineco Basic tubing bender that was damaged by a leaking
3.6 V 80 mAh NiMH battery. That leak cost a local business $700 for a
failed $5 battery. The tool was eight years old. I called them
yesterday and told them to log the date the board was installed, and to
have me replace it in two years as PM. The symptoms were that the
machine started bending the wrong angles, and different angles without
changing the setup. A trace below the battery was eaten by the leaking
chemicals. I'll try to get a good photo before I return it to them. It
might save someone else a wad of cash, or convince a shop owner to let
you check for leaking batteries. The machine was used on a regular
business, a few days per week, so it wasn't caused by long term storage.


--
You can't have a sense of humor, if you have no sense.

[Jim Yanik]

Jeff Liebermann <je...@cruzio.com> wrote in

news:m80lc75dhftjsj5n4...@4ax.com:

I'd not go by Wikipedia,I'd go by the actual WD-40 MSDS.
if you read the MSDS -for each ingredient- listed for WD-40 on the WD-
40 MSDS(like I did),you'll see that it's mostly kerosene.

[Dave Platt]

In article <Xns9FA57C50659FC...@216.168.3.44>,

Jim Yanik <jya...@abuse.gov> wrote:

>> USA MSDS sheet:
>><http://www.wd40company.com/files/pdf/msds-wd494716385.pdf>
>>
>> The key ingredient is a sulfactant (wetting agent), to reduce surface
>> tension and make it "cling" to objects and "puddle" water. My
>> guess(tm) the reason it took 40 trys is that they had a difficult time
>> finding one that would work in a solvent solution.
>>
>
>
>I'd not go by Wikipedia,I'd go by the actual WD-40 MSDS.
>if you read the MSDS -for each ingredient- listed for WD-40 on the WD-
>40 MSDS(like I did),you'll see that it's mostly kerosene.

I don't see either kerosene, or Stoddard solvent, by name in the MSDS.

Rather, I see "Aliphatic hydrocarbon" (CAS #64742-47-8) as the
ingredient with the highest concentration. Commonest synonym seems to
be "Hydrotreated light petroleum distillates." Usable as fuel oil or
solvent.

If I understand correctly, all of these petroleum distillates form a
continuum - most are mixtures of hydrocarbons with differing molecular
weights. I don't think there's a sharp physical cutoff between what
constitutes a "kerosene" and a "solvent" - it's all a matter of
convention.

According to the MSDS, WD-40 is a bit more than half solvent (about an
eighth is "LVP", presumably slower to evaporate?), about a quarter
light lubricating oil, a couple of percent of the secret-sauce
surfactant that Jeff was alluding to, CO2 for pressurization, and 10%
mixed "non-hazardous ingredients."

--
Dave Platt <dpl...@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

[Jeff Liebermann]

On Tue, 22 Nov 2011 11:30:34 -0800, dpl...@radagast.org (Dave Platt)
wrote:

Well, let's dive a bit deeper into the contents. The CAS number
identifies the exact ingredients. We have:
CAS % by weight
Aliphatic Hydrocarbon 64742-47-8 45-50%
That would be:
<http://www.cdc.gov/niosh/ipcsneng/neng1379.html>
Low odor paraffinic solvent, Dearomatized kerosine, Deodorized
kerosene. In other words, lamp oil as used in a kerosene lamp.

Petroleum Base Oil <25%
64742-58-1 Recycled motor oil
64742-53-6 Distillates(petroleum), hydrotreated light naphthenic.
Also known as Coleman fuel
64742-56-9 Solvent-dewaxed light paraffinic.
64742-65-0 Solvent-dewaxed heavy paraffinic.

LVP Aliphatic Hydrocarbon 12-18%
64742-47-8 Same as the first item. Kerosene.
My guess is that LVP means "low vapor pressure" which for solvents
means that it's slow to evaporate.

(gotta run...)

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com je...@cruzio.com
# http://www.LearnByDestroying.com AE6KS

[DoN. Nichols]

On 2011-11-22, dagmarg...@yahoo.com <dagmarg...@yahoo.com> wrote:
> On Nov 21, 9:08 pm, "DoN. Nichols" <BPdnichol...@d-and-d.com> wrote:
>> On 2011-11-21, dagmargoodb...@yahoo.com <dagmargoodb...@yahoo.com> wrote:

[ ... ]

>> > I sometimes think about wiring up a "AAA" or solar cell and just
>> > forgetting it, but for $0.50 a year it's not worth the trouble.
>>
>>         Actually -- there *are* some "solar powered" ones -- by Mitutoyo
>> IIRC.  They would probably be excellent used daily in a well-illuminated
>> shop.
>
> I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
> resisted. Something about having a glass window on a machine tool
> close to all that hard steel just didn't sit well--it brought up
> memories of scratched and broken watch crystals.

I've seen them only new, and decided that in my shop conditions,
they would not work very well. :-)

> OTOH, I paid $10 for most of my HF calipers. Those you can take
> chances with. Using the 8x25mm solar panel from a $1 calculator, a
> super capacitor for storage, and an LED as a regulator diode was my
> notion. $2 in parts, $500 labor ;-).

O.K. Do you know the maximum voltage that the solar panel is
likely to produce? And the voltage drop on the LED? I know that
silicon diodes are typically between 600 mV and 750 mV. Also, any clues
as to the maximum voltage that the calipers can tolerate long term?

[ ... ]

>>         I did recently get an auto-darkening welding hood from Harbor
>> Freight which is solar powered, and based on what I have read about them
>> dying if not used regularly, I've put mine on a folding workstool facing
>> out the window so it sees daylight to maintain the charge.  I'll proably
>> eventually have to perform surgery and replace the rechargeable cells in
>> there.  There is a temptation to provide a connection for an AC-powered
>> trickle charger so I can store it more conveniently.  What would be
>> particularly nice would be an induction coupled charger like those for
>> electric toothbrushes.  Just put it on a stand and expect it to be fully
>> charged when I come back.
>>
>>         If the charge is good enough to work on the first strike, it
>> should work fine for the rest of the day, because it will be getting a
>> charge boost from the arc -- close enough to vigorous sunlight. :-)
>
> Sounds like a LiIon cell. If so, those can't be allowed to go dead,
> as you've surmised.

And -- they are supposedly not replaceable according to the
manual. :-) (You've got to cut the package apart to get to them.) There
is a web page describing how someone opened one up and set a holder for
two AA cells outside the package. I'm really tempted to go for the
induction charger when I finally have to dig into mine. But it is
significantly less expensive than auto-darkening ones from MSC -- to the
point where three HF ones match the cost of one from MSC. :-)

[DoN. Nichols]

On 2011-11-22, P E Schoen <pa...@pstech-inc.com> wrote:

> "DoN. Nichols" wrote in message
> news:slrnjcm1ee.op...@Katana.d-and-d.com...

[ ... ]

>> If you are going to leave the calipers for more than a week,
>> pull the cell(s) and store them separately -- perhaps in a small
>> zip-loc baggie, so they don't damage anything else when leaking.
>
> That's what I am going to do. There is a cutout in the foam of the caliper
> case for a spare. I also put the other three cells in their original
> packaging in there. I plan to use the calipers more now that I can depend on
> them (and know how to fix them). Usually I don't do much precision
> machining, and I have a cheap plastic dial caliper that is good to about
> 0.01" and is immune to humidity and most abuse.

Except for certain solvents. :-)

Good Luck,

[dagmarg...@yahoo.com]

On Nov 22, 9:21 pm, "DoN. Nichols" <BPdnichol...@d-and-d.com> wrote:

> On 2011-11-22, dagmargoodb...@yahoo.com <dagmargoodb...@yahoo.com> wrote:

> > I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
> > resisted.  Something about having a glass window on a machine tool
> > close to all that hard steel just didn't sit well--it brought up
> > memories of scratched and broken watch crystals.
>
>         I've seen them only new, and decided that in my shop conditions,
> they would not work very well. :-)
>
> > OTOH, I paid $10 for most of my HF calipers.  Those you can take
> > chances with.  Using the 8x25mm solar panel from a $1 calculator, a
> > super capacitor for storage, and an LED as a regulator diode was my
> > notion. $2 in parts, $500 labor ;-).
>
>         O.K.  Do you know the maximum voltage that the solar panel is
> likely to produce?  And the voltage drop on the LED?  I know that
> silicon diodes are typically between 600 mV and 750 mV.  Also, any clues
> as to the maximum voltage that the calipers can tolerate long term?

The max. solar panel voltage doesn't matter--the LED regulator clamps
the solar panel voltage, taking care of that.

Here's a sketch:

D1
.--|>|--+-----+----> (+) to caliper
+ | | |
.------. + | |
| | --- ---
| ---- | --- \ / ~~>
| | C1| ---
| ---- | | | LED (red)
| | | |
'------' | |
- | PV | |
'--------+-----+---> (-) to caliper


C1 - A capacitor to power the caliper during momentary outages.
Optionally a super-cap., e.g. http://www.goldmine-elec-products.com/prodinfo.asp?number=G13133
(Note1: The PV will take HOURS of bright light to charge a super-
cap, so you might want to precharge the cap, then let the PV just
float it.)
(Note2: Super-caps have significant electrical leakage. If your
cap is too leaky, it'll never charge, and you'll be disappointed. I
haven't measured the above-linked PAS920 to see if this is the case.)

PV - http://www.goldmine-elec-products.com/prodinfo.asp?number=G17448,
or, stolen from the cheapest solar-powered calculator you can find.
Walmart and the dollar stores have some good candidates.
LED - shunt-regulates the PV output to a safe voltage.
D1 - 1n4148, prevents PV from draining a super-cap C1 when dark,
possibly not needed. (Depends on PV panel's dark leakage current.)


To set the voltage you'd choose an LED with a forward voltage of, say
1.6-1.8v. Three ordinary small-signal silicon diodes in series (e.g.
1n4148) wouldn't be a bad choice either. With surface-mount parts,
the ckt can be tiny.

If the voltage is too high it's not a matter of "long-term," the
caliper will die instantly. I don't know what that voltage is, but
I'd easily wager one of *my* $10 calipers that 2v is okay, and I'd
wager one of *yours* that 2.5v might be okay too. ;-)

--
Cheers,
James Arthur

[Bob Engelhardt]

dagmarg...@yahoo.com wrote:
...

>
> D1
> .--|>|--+-----+----> (+) to caliper
> + | | |
> .------. + | |
> | | --- ---
> | ---- | --- \ / ~~>
> | | C1| ---
> | ---- | | | LED (red)
> | | | |
> '------' | |
> - | PV | |
> '--------+-----+---> (-) to caliper
>

...

Doncha' need a current limiter on the LED?

Bob

[John S]

Not if the PV cell's rated SC current is less than the max LED current
rating.

[Winston]

Nup. It's a 'shunt regulator'.
http://en.wikipedia.org/wiki/Linear_regulator#Simple_zener_regulator

--Winston

[Winston]

dagmarg...@yahoo.com wrote:

(...)

> I saw a solar-powered Mitutoyo at a flea market and was intrigued, but
> resisted.

Next time, advise jump on it before someone else does.

I have two of those. They just keep working without
any issues. Well, except for turning off in low-light
situations. I just charge it up with the flashlight
and it works just fine. 'Way better than having to
run to the store for a $5 battery! They are fine tools
and have my highest recommendation.

--Winston

[dagmarg...@yahoo.com]

On Nov 23, 3:05 pm, Bob Engelhardt <bobengelha...@comcast.net> wrote:

Nope. These little PV panels barely manage 1 or 2 mA even in
sunlight, 20uA under fluorescent. The LED's good for 10x the PV's
max. output.

I dragged an old calculator panel out[*] and connected it to one of
those 0.6F super caps. It's charging the cap 1mV/8s, with no load.

[*] this panel is 10x55mm--much larger than the one I referenced. I
have several of the smaller ones, but they're all still working hard
in $1 Walmart calculators.


It's pretty impractical (clunky, delicate), but fun.


--
Cheers,
James Arthur

[dagmarg...@yahoo.com]

On Nov 23, 4:03 pm, Winston <Wins...@BigBrother.net> wrote:

Yes, but I got one of the HF's and hacked it up with a Dremel tool, to
mount to the lathe.

Can't do that with a Mitutoyo!

--
Cheers,
James Arthur

[Bob Engelhardt]

John S wrote:
> On 11/23/2011 2:05 PM, Bob Engelhardt wrote:

>> Doncha' need a current limiter on the LED?

>

> Not if the PV cell's rated SC current is less than the max LED current
> rating.

Isn't the capacitor's rated current MUCH more than the LED's? Bob

[Bob Engelhardt]

Winston wrote:

> Bob Engelhardt wrote:
>> Doncha' need a current limiter on the LED?

> Nup. It's a 'shunt regulator'.
> http://en.wikipedia.org/wiki/Linear_regulator#Simple_zener_regulator

The wiki ckt has a current-limiting resistor in series with the voltage
source. Not so the posted ckt.

Bob

[Winston]

dagmarg...@yahoo.com wrote:

(...)

> Yes, but I got one of the HF's and hacked it up with a Dremel tool, to
> mount to the lathe.
>
> Can't do that with a Mitutoyo!

And hold one's head up in public, that is. :)

--Winston

[Winston]

It *is* in the posted circuit.
Sort of. :)

As James mentions, the internal resistance of the PV
cell is the current-limiting resistor.

--Winston <--The BSA B50T POS used a single power
zener across the battery as it's only
voltage regulator.

[Bob Engelhardt]

Winston wrote:
> Bob Engelhardt wrote:
>> The wiki ckt has a current-limiting resistor in series with the voltage
>> source. Not so the posted ckt.

> It *is* in the posted circuit.
> Sort of. :)
>
> As James mentions, the internal resistance of the PV
> cell is the current-limiting resistor.

I meant the capacitor voltage source. Is its internal resistance a
sufficient current limiter? I'm not familiar with super caps, but the
common ones that I am familiar with will supply huge currents, momentarily.

Bob

[Jamie]

Hey, that's one hell of an idea! :)

Jamie

[Winston]

This circuit, yes?

D1
.--|>|--+-----+----> (+) to caliper
+ | | |
.------. + | |
| | --- ---
| ---- | --- \ / ~~>
| | C1| ---
| ---- | | | LED (red)
| | | |
'------' | |
- | PV | |
'--------+-----+---> (-) to caliper

Under no circumstances would the voltage across
the LED (and capacitor) go above, say 1.8 V
because the LED turns any additional
voltage into current. In order for C1 to produce
a current large enough to endanger the LED or
the caliper, it would have to be allowed to charge
significantly above the 'zener point' of the LED.
It just cannot.


--Winston

[John S]

What has that to do with it? The voltage is clamped. What are you missing?

[Ron D.]

I get my LR44's and CR2032's here: http://www.infinitelights.com/alkalinewatchbatteries.html

Orders > $20 ship free. I use more CR2032's.

[Bob Engelhardt]

Winston wrote:
> This circuit, yes?
>
> D1
> .--|>|--+-----+----> (+) to caliper
> + | | |
> .------. + | |
> | | --- ---
> | ---- | --- \ / ~~>
> | | C1| ---
> | ---- | | | LED (red)
> | | | |
> '------' | |
> - | PV | |
> '--------+-----+---> (-) to caliper
>
>
> Under no circumstances would the voltage across
> the LED (and capacitor) go above, say 1.8 V
> because the LED turns any additional

> voltage into current. ...

Oh ... right ... yeah. Dope slap for me. Bob

[Winston]

Bob Engelhardt wrote:
> Winston wrote:
>> This circuit, yes?

(...)

>> Under no circumstances would the voltage across
>> the LED (and capacitor) go above, say 1.8 V
>> because the LED turns any additional
>> voltage into current. ...
>
> Oh ... right ... yeah.

We are all here to learn. :)

--Winston

[Jeff Liebermann]

On Wed, 23 Nov 2011 06:45:46 -0800 (PST), dagmarg...@yahoo.com
wrote:

>The max. solar panel voltage doesn't matter--the LED regulator clamps
>the solar panel voltage, taking care of that.

Yeah, but shunt regulators and leaky super-caps are not really
appropriate for micropower devices. They waste power.

In a previous message, James Arthur measured:
Drain: 13.5uA (off), 14.5uA (on)
Battery low threshold (blinking display): 1.37V
Lowest operating voltage: 1.01V

Nominal voltage on a silver oxide battery is 1.5V. Therefore, the
operating power is:
1.5VDC * 15uA = 22.5 microwatts.
From the standpoint of a resistive load, that's about:
1.5VDC / 15 uA = 100K ohms

The first question is whether a small solar cell will product 22.5
microwatts. Testing a somewhat oversized polycrystaline cell that I
found in my junk box (quality unknown), it produces 3.0VDC at 6ma with
a short circuit load (my milliamps guesser). My guess(tm) is that
this cell is about three times as big as will conveniently fit on the
calipers, so I'll just cut the current to 2ma . Delivered power with
my desk lamp is 6 milliwatts. Yeah, it will a 22.5 microwatt load.

The next question is for how long will it run? Assuming the calipers
can handle 3.0VDC without damage, how long will a junk 100UF
electrolytic cap run the calipers?
<http://www.kpsec.freeuk.com/capacit.htm>
From 1.37V is roughly 50% of full 3.0VDC charge. That's about 80% of
1RC time constant. 1RC is:
0.8 * 100K * 1000uF = 80 seconds
That's probably enough to make a few measurements. Any longer and a
super-cap will probably be needed. Picking 50% of full charge out of
the hat is rather convenient, as it makes the time to charge from zero
to the dropout point the same 80 seconds (yes, I'm lazy). Whether the
user really wants to wait 1.5 minutes under a desk lamp for the
calipers to be usable is dubious. Of course, a longer run time, means
a longer charge time. For example, a 1F 5V 1ua leakage super-cap,
will run the calipers for 80,000 seconds, but will also take 80,000
seconds to charge.

There are low voltage DC-DC boost/buck switching regulator chips
available that can tolerate a wide range of input voltages, and
deliver a constant 1.5VDC.

In my never humble opinion, what makes more sense is to do it exactly
like the typical solar powered calculator. They all have one or two
LR44 batteries inside. However, the solar cell does NOT charge the
battery. When you turn the calculator on, and there's enough light to
run from the solar cell, the battery is essentially disconnected. When
there's not enough light to run the calculator, it runs off the
battery. No waiting to charge a capacitor from the solar cell.

If you're into high tech, there are various energy scavenging devices
that can also power the calipers.
<http://en.wikipedia.org/wiki/Energy_harvesting>
With only 22.5 microwatts required, it might be possible to power the
device with a wind up key, piezo pressure, body heat, kinetic magnetic
generator, etc. I kinda like the idea of a wind up caliper.

Happy Day of the Turkeys.



--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[dagmarg...@yahoo.com]

On Nov 24, 5:20 pm, Jeff Liebermann <je...@cruzio.com> wrote:
> On Wed, 23 Nov 2011 06:45:46 -0800 (PST), dagmargoodb...@yahoo.com

> wrote:
>
> >The max. solar panel voltage doesn't matter--the LED regulator clamps
> >the solar panel voltage, taking care of that.
>
> Yeah, but shunt regulators and leaky super-caps are not really
> appropriate for micropower devices.  They waste power.

Small, cheap and simple are the main factors here. The r.c.m. guys
aren't going to be building switching regulators, and switching
regulators generally aren't more efficient at these power levels
anyhow--their quiescent current draw's too high.

(I've made a study of designing microwatt switchers, from scratch.
It's possible, but wholly inappropriate here.)

> In a previous message, James Arthur measured:
>   Drain: 13.5uA (off), 14.5uA (on)
>   Battery low threshold (blinking display): 1.37V
>   Lowest operating voltage: 1.01V
>
> Nominal voltage on a silver oxide battery is 1.5V.  Therefore, the
> operating power is:
>    1.5VDC * 15uA = 22.5 microwatts.
> From the standpoint of a resistive load, that's about:
>    1.5VDC / 15 uA = 100K ohms
>
> The first question is whether a small solar cell will product 22.5
> microwatts.  Testing a somewhat oversized polycrystaline cell that I
> found in my junk box (quality unknown), it produces 3.0VDC at 6ma with
> a short circuit load (my milliamps guesser).  My guess(tm) is that
> this cell is about three times as big as will conveniently fit on the
> calipers, so I'll just cut the current to 2ma .  Delivered power with
> my desk lamp is 6 milliwatts.  Yeah, it will a 22.5 microwatt load.

Not so fast... The advantage of the thin-film PV panels is that
(appropriate) panels excel at producing power even in dim light.
Polycrystalline silicon panels don't.

The array I suggested for experimentation is thin-film for that
reason--so it can work in indoor light levels.

> The next question is for how long will it run?  Assuming the calipers
> can handle 3.0VDC without damage, how long will a junk 100UF
> electrolytic cap run the calipers?

a) How long will it run? Not nearly long enough, and b) 3.0VDC is
waayyy too risky for my blood. 20uA will discharge 100uF from 2.0V to
1.35V in 3.25 seconds.

Of the setup I suggested, the most marginal part is the itty bitty PV
panel (its output is on the low side). Dark leakage on my much-larger
10x55mm calculator panel is about 8uA @ 1.7V bias.

The supercap works wonderfully well. Charge 0.6F to 1.8V, and you've
got 4 hours' runtime until you reach the 1.35V battery-low display-
starts-blinking level. (Assuming 20uA total draw, to allow for some
leakage.)

> <http://www.kpsec.freeuk.com/capacit.htm>
> From 1.37V is roughly 50% of full 3.0VDC charge.  That's about 80% of
> 1RC time constant.  1RC is:
>    0.8 * 100K * 1000uF = 80 seconds
> That's probably enough to make a few measurements.  Any longer and a
> super-cap will probably be needed.  Picking 50% of full charge out of
> the hat is rather convenient, as it makes the time to charge from zero
> to the dropout point the same 80 seconds (yes, I'm lazy).  Whether the
> user really wants to wait 1.5 minutes under a desk lamp for the
> calipers to be usable is dubious.  Of course, a longer run time, means
> a longer charge time.  For example, a 1F 5V 1ua leakage super-cap,
> will run the calipers for 80,000 seconds, but will also take 80,000
> seconds to charge.

Not 80,000s. Expose the PV to sunlight (or directly to a lamp), and
it'll charge (initially) >50x faster. You'd only have to do that
once. Indoors, the PV would keep it topped off, that's the idea.

Alternatively, an electrolytic works, but gives a caliper that quickly
quits if you accidentally shadow it.

There are much smaller supercaps--0.02F--used in cellphones. That's
another option / compromise. Leakage should be better too.

> There are low voltage DC-DC boost/buck switching regulator chips
> available that can tolerate a wide range of input voltages, and
> deliver a constant 1.5VDC.
>
> In my never humble opinion, what makes more sense is to do it exactly
> like the typical solar powered calculator.  They all have one or two
> LR44 batteries inside.  However, the solar cell does NOT charge the
> battery.  When you turn the calculator on, and there's enough light to
> run from the solar cell, the battery is essentially disconnected. When
> there's not enough light to run the calculator, it runs off the
> battery.  No waiting to charge a capacitor from the solar cell.

That uses the PV as, basically, a battery-extender. That's fine, but
complex--you need a micro-power switch to disconnect the battery, etc.
(A diode drops waayyy too much voltage.) That puts it out of the
realm of a simple project that can fit into the existing caliper.

> If you're into high tech, there are various energy scavenging devices
> that can also power the calipers.
> <http://en.wikipedia.org/wiki/Energy_harvesting>
> With only 22.5 microwatts required, it might be possible to power the
> device with a wind up key, piezo pressure, body heat, kinetic magnetic
> generator, etc.  I kinda like the idea of a wind up caliper.

Windup would be fun--steampunk.

The "real" solution is to design the caliper to draw less current in
the first place, like Mitutoyo and Starrett. If you've done that,
solar-powering is a snap, but then, if the battery lasts years, you
don't need solar power, do you?

--
Cheers,
James Arthur

[DoN. Nichols]

The capacitor gets its voltage from the PV cell. Assuming that
you don't put a switch between the LED and the cap (there is none shown
in the schematic), the cap will never charge high enough to be able to
damage the LED, because the LED will have already clamped the maximum
voltage based on the current limit of the PV cell. Not sure what would
happen with the PV cell close to an arc welding process like a TIG -- it
depends on the internal resistance of the PV cell and the peak voltage
which the PV cell can produce with such excessive illumination.

[Jeff Liebermann]

On Thu, 24 Nov 2011 18:13:15 -0800 (PST), dagmarg...@yahoo.com
wrote:

I found this, which calculates and measures caliper battery life:
<http://www.davehylands.com/Machinist/Caliper-Batteries/>

>Small, cheap and simple are the main factors here. The r.c.m. guys
>aren't going to be building switching regulators, and switching
>regulators generally aren't more efficient at these power levels
>anyhow--their quiescent current draw's too high.

True. However, switching regulators usually have some manner of load
shedding when the supply voltage is insufficient. Below that
threshold, the current drain is usually in nanoamps.

>(I've made a study of designing microwatt switchers, from scratch.
>It's possible, but wholly inappropriate here.)

You're ahead of me. I've never designed anything in that low power
class. Different world. Can you point me to a suitable (or close to
suitable) regulator chip?

>Not so fast... The advantage of the thin-film PV panels is that
>(appropriate) panels excel at producing power even in dim light.
>Polycrystalline silicon panels don't.
>The array I suggested for experimentation is thin-film for that
>reason--so it can work in indoor light levels.

Decisions, decisions, and more decisions. Polycrystaline has a cost
advantage and is more efficient than single layer thin-film. Well, if
I wanted to go cheap, I would use amorphous cells and mold them into
the plastic case. For small solar cells, the cost of monocrystaline
isn't all that much more (i.e. most of the cost is in packaging and
handling) but won't work well with indoor lighting. So, I guess
thin-film is the least disgusting.
<http://en.wikipedia.org/wiki/Solar_powered_calculator>
"Solar calculators may not work well in indoor
conditions under ambient lighting as sufficient lighting
is not available."

>> The next question is for how long will it run?  Assuming the calipers
>> can handle 3.0VDC without damage, how long will a junk 100UF
>> electrolytic cap run the calipers?
>
>a) How long will it run? Not nearly long enough, and b) 3.0VDC is
>waayyy too risky for my blood. 20uA will discharge 100uF from 2.0V to
>1.35V in 3.25 seconds.

I used 1000uF elsewhere in my calcs, but slipped here and used 100uF
instead. Sorry.

I think you might be a bit too conservative. 5ua leakage is high.
Most of the spec sheets I've skimmed show 1-2ua for a typical 1F 5.5V
super-cap.

>Of the setup I suggested, the most marginal part is the itty bitty PV
>panel (its output is on the low side). Dark leakage on my much-larger
>10x55mm calculator panel is about 8uA @ 1.7V bias.

The alternative is to lose approximately 0.3V in a series Schottky
diode. That's about 20% of the power budget, which is probably too
much.

>The supercap works wonderfully well. Charge 0.6F to 1.8V, and you've
>got 4 hours' runtime until you reach the 1.35V battery-low display-
>starts-blinking level. (Assuming 20uA total draw, to allow for some
>leakage.)

Ok. You've sold me. I was trying to see what could be done with
commodity electrolytic caps. Also, super-caps fail to appreciate high
humidity, which may become a problem.

>> <http://www.kpsec.freeuk.com/capacit.htm>
>> From 1.37V is roughly 50% of full 3.0VDC charge.  That's about 80% of
>> 1RC time constant.  1RC is:
>>    0.8 * 100K * 1000uF = 80 seconds
>> That's probably enough to make a few measurements.  Any longer and a
>> super-cap will probably be needed.  Picking 50% of full charge out of
>> the hat is rather convenient, as it makes the time to charge from zero
>> to the dropout point the same 80 seconds (yes, I'm lazy).  Whether the
>> user really wants to wait 1.5 minutes under a desk lamp for the
>> calipers to be usable is dubious.  Of course, a longer run time, means
>> a longer charge time.  For example, a 1F 5V 1ua leakage super-cap,
>> will run the calipers for 80,000 seconds, but will also take 80,000
>> seconds to charge.
>
>Not 80,000s. Expose the PV to sunlight (or directly to a lamp), and
>it'll charge (initially) >50x faster. You'd only have to do that
>once. Indoors, the PV would keep it topped off, that's the idea.

Yep. However, I screwed up. The discharge load is:
1.5VDC / 15uA = 100K ohms
However, the charging ESR is much less.
3.0VDC / 2ma = 1.5K
It will certainly be higher a lower illumination levels. Checking my
junk cell under random room lighting conditions, and again scaling for
size, I get:
0.333 * 0.55v / 0.02mA = 9.2K
I don't have a small thin film panel to test. (I have 90watt panel,
but that's a bit much for scaling to caliper size).

>Alternatively, an electrolytic works, but gives a caliper that quickly
>quits if you accidentally shadow it.

Not if you do exactly like it's done with a calculator. When the cell
is shaded, it runs on battery. A silver-oxide battery holds:
1.5v * 150 mA-Hr = 22.5 milliwatt-Hrs
and will deliver most of that before the voltage drops to unusable
levels.

The super cap will deliver (very roughly):
1.5v * 15uA * 4Hr = 90 microwatt-Hrs

>There are much smaller supercaps--0.02F--used in cellphones. That's
>another option / compromise. Leakage should be better too.

Overview of CDE super-caps:
<http://www.cde.com/catalogs/EDL.pdf>
Some interesting notes on charge time and lifetime near the bottom.

>> In my never humble opinion, what makes more sense is to do it exactly
>> like the typical solar powered calculator.  They all have one or two
>> LR44 batteries inside.  However, the solar cell does NOT charge the
>> battery.  When you turn the calculator on, and there's enough light to
>> run from the solar cell, the battery is essentially disconnected. When
>> there's not enough light to run the calculator, it runs off the
>> battery.  No waiting to charge a capacitor from the solar cell.
>
>That uses the PV as, basically, a battery-extender. That's fine, but
>complex--you need a micro-power switch to disconnect the battery, etc.
>(A diode drops waayyy too much voltage.) That puts it out of the
>realm of a simple project that can fit into the existing caliper.

There has to be a chip in the calipers anyway to count pulses, run the
display, and deal with the push buttons. Adding a power management
feature does not add much real estate or complexity. However, if
you're thinking of a retrofit, I suspect something could be done with
a separate switcher chip.

>> If you're into high tech, there are various energy scavenging devices
>> that can also power the calipers.
>> <http://en.wikipedia.org/wiki/Energy_harvesting>
>> With only 22.5 microwatts required, it might be possible to power the
>> device with a wind up key, piezo pressure, body heat, kinetic magnetic
>> generator, etc.  I kinda like the idea of a wind up caliper.
>
>Windup would be fun--steampunk.

In the late 1960's, I designed and built a paging receiver, that
produced the message output on a 1/4" wide roll of paper tape. Battery
power to the mechanics for such a portable device was impossible. So,
I went to a wind up coil spring mechanism. I've been somewhat of a
fan of spring power ever since.

>The "real" solution is to design the caliper to draw less current in
>the first place, like Mitutoyo and Starrett. If you've done that,
>solar-powering is a snap, but then, if the battery lasts years, you
>don't need solar power, do you?

Agreed. It would be like a digital watch, which typically has a 10
year battery life. However, the solar cell is still a problem because
of the dark current (reverse leakage). An isolating Schottky diode
can reduce that, but then the solar cell would need to be about 20%
larger to compensate for the added loss.

Another problem is that it would be no fun. Windup calipers offer a
far more entertaining problem to solve.

[Jeff Liebermann]

On Thu, 24 Nov 2011 21:46:48 -0800, Jeff Liebermann <je...@cruzio.com>
wrote:

>>> The next question is for how long will it run?  Assuming the calipers
>>> can handle 3.0VDC without damage, how long will a junk 100UF
>>> electrolytic cap run the calipers?
>>
>>a) How long will it run? Not nearly long enough, and b) 3.0VDC is
>>waayyy too risky for my blood. 20uA will discharge 100uF from 2.0V to
>>1.35V in 3.25 seconds.

Trying the same calc using the super-cap formula from Pg 6 of:
<http://www.cde.com/catalogs/EDL.pdf>

t = C delta V / I
t = C[V0-(i*R)-V1] / (i+iL)
where:
t: Back-up time (sec)
C: Capacitance of Type EDL (Farads)
V0: Applied voltage (Volts)
V1: Cut-off voltage (Volts)
i: Current during back-up (Amps)
iL: Leakage current (Amps)
R: Internal resistance (ohms) at 1 kHz

For this example, I'll use a 0.1F (type F) 5.5V 100 ohm cap.
The low end of the tolerance range might drop this to 0.08F.
V0 = 2.0V, V1 = 1.4V, i = 15uA, iL = 2uA

Plugging in:
t = C[V0-(i*R)-V1] / (i+iL)
t = 0.08F[2.0V-(15uA*100ohms)-1.4V]/(15uA+2uA)
t = 2800 sec = 47 minutes.
Not bad.

I guess the protective case that most calipers use will need a clear
plastic window to keep it charged. Maybe another window on top of my
toolbox.

[Gunner Asch]

On Thu, 24 Nov 2011 22:29:50 -0800, Jeff Liebermann <je...@cruzio.com>

http://www.judgetool.com/500seriessupercaliper-solarpoweredip67.aspx

http://www.widgetsupply.com/page/WS/PROD/caliper-digital/BAP30
(only 2 digits)

http://www.alibaba.com/showroom/solar-power-digital-caliper.html

Quite a number of them.....


One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch