LM723 Based Power Supply
Anand P. Paralkar
I need to build my own power supply. I need a proven circuit for 0 to
30V DC variable power supply with minimum 2.5 A current output.
I thought I had hit on something good here:
http://www.next.gr/inside-circuits/0-30-Volts-2-5A-Variable-Power-Supply-l4107.html
But then, I see some comments on this page saying that there could be
errors in the circuit.
Could some expert(s) please confirm that this circuit would work fine?
(Or point to something better.)
Thanks for your help.
Thanks,
Anand
John Fields
<anand.p...@gnospammale.com> wrote:
>Hi Everybody,
>
>I need to build my own power supply. I need a proven circuit for 0 to
>30V DC variable power supply with minimum 2.5 A current output.
---
So what's the maximum output current?
---
JF
Tim Wescott
As mentioned in the comments, the base drive transistor is reversed, the
current limit has no fold-back and therefore isn't safe if you have a
short circuit or very low impedance load, and you won't be getting the
most out of your pass transistor because you're driving your regulator
IC and base drive transistor from the same source as the collector of
your pass transistor.
I'd suggest you get a copy of the ARRL handbook, which has a number of
power supply designs presented along with explanations of _why_ things
are done the way they're done.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
Jim Thompson
wrote:
>On 10/18/2010 11:13 AM, Anand P. Paralkar wrote:
>> Hi Everybody,
>>
>> I need to build my own power supply. I need a proven circuit for 0 to
>> 30V DC variable power supply with minimum 2.5 A current output.
>>
>> I thought I had hit on something good here:
>>
>>
>> http://www.next.gr/inside-circuits/0-30-Volts-2-5A-Variable-Power-Supply-l4107.html
>>
>>
>> But then, I see some comments on this page saying that there could be
>> errors in the circuit.
>>
>> Could some expert(s) please confirm that this circuit would work fine?
>> (Or point to something better.)
>
>As mentioned in the comments, the base drive transistor is reversed, the
>current limit has no fold-back and therefore isn't safe if you have a
>short circuit or very low impedance load, and you won't be getting the
>most out of your pass transistor because you're driving your regulator
>IC and base drive transistor from the same source as the collector of
>your pass transistor.
>
>I'd suggest you get a copy of the ARRL handbook, which has a number of
>power supply designs presented along with explanations of _why_ things
>are done the way they're done.
Fold-back can be very tricky to implement and keep stable _and_ get
reliable start-up.
I prefer thermal or current-limit-induced snap-off, requiring a reset.
I don't know why people insist on using such crap as the 723, when you
can do much better with a TL431 and a few discrete transistors.
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I can see November from my house :-)
Rich Webb
<anand.p...@gnospammale.com> wrote:
The datasheet <http://www.national.com/mpf/LM/LM723.html#Overview> has
some example designs that can give you a place to start.
--
Rich Webb Norfolk, VA
Tim Wescott
Probably because of all the circuits out there based on the 723, and the
seductive power of a "one chip does all" application (never mind that
it's a "one chip does all in a mediocre way")
Nico Coesel
>Hi Everybody,
>
>I need to build my own power supply. I need a proven circuit for 0 to
>30V DC variable power supply with minimum 2.5 A current output.
>
>(Or point to something better.)
IIRC there is also an LM350. Much easier but it won't go below 1.25V.
Another problem is power dissipation. You probably need some circuitry
to switch the secondary transformer turns.
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------
Phil Hobbs
The 723 does have a buried-zener reference, though, so it's probably a
lot quieter than a TL431. I might have to switch to that as a jellybean
quiet reference if the LM329 goes away!
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
whit3rd
<anand.paral...@gnospammale.com> wrote:
> I need to build my own power supply. I need a proven circuit for 0 to
> 30V DC variable power supply with minimum 2.5 A current output.
If it needs to be 'proven', you need to BUY, not build.
30VDC output means at least 33V input, and at low-voltage
that puts out 33V x 2.5A = 82W, which means a single
inexpensive transistor isn't gonna handle the output.
There's a half dozen tricks that will help: the input power
can be transformer-tap-selected to lower the waste, or
the pass transistors can be substituted with regulator
ICs (which have inbuilt thermal limiting and won't burn up),
or you can use two regulators with different voltage
ranges, and diode-isolate so they share the output pin.
The easiest thing to do, though, is just to make a brute-force
DC power supply, and plug it into a Variac when you want to
adjust it. That works, it's efficient, and the Variac (variable
autotransformer) comes in handy for lots of other things.
Bill Bowden
>
> I need to build my own power supply. I need a proven circuit for 0 to
> 30V DC variable power supply with minimum 2.5 A current output.
>
> I thought I had hit on something good here:
>
>
> But then, I see some comments on this page saying that there could be
> errors in the circuit.
>
> Could some expert(s) please confirm that this circuit would work fine?
> (Or point to something better.)
>
> Thanks for your help.
>
> Thanks,
> Anand
You might try the LM338K adjustable regulator, 5 Amp, built in thermal
and current limiting. Adjusts from 1.2 to 30 volts with a few parts -
4 caps, 1 resistor and pot, bridge rectifier, and the 338 on a 100
watt heatsink.
http://www.aaroncake.net/circuits/supply1.gif
-Bill
whit3rd
wrote:
> You might try the LM338K adjustable regulator, 5 Amp, built in thermal
> and current limiting. Adjusts from 1.2 to 30 volts with a few parts -
> 4 caps, 1 resistor and pot, bridge rectifier, and the 338 on a 100
> watt heatsink.
Even with an infinite heatsink, this part cannot (there's a graph
in the data sheet) manage 2.5A if the in/out difference gets
as high as 25V. Reference accuracy is only about +/- 5% over
temperature, if that matters (the uA723 is better).
Richard Torrens (News)
>
> http://www.next.gr/inside-circuits/0-30-Volts-2-5A-Variable-Power-Supply-l4107.html
> Thanks for your help.
> Thanks,
> Anand
Have a look at
www.4QDTEC.com
Several power suppplies there.
--
------------------------------------------------------------------
Richard Torrens. News email address is valid - for a limited time only.
http://www.Torrens.org.uk for genealogy, natural history, wild food, walks, cats
and more!
Hammy
news:604e1c03-7fe6-4ba7-a59d-
936c89...@e14g2000yqe.googlegroups.co
m:
> On Oct 18, 11:13�am, "Anand P. Paralkar"
> <anand.paral...@gnospammale.com> wrote:
>
>> I need to build my own power supply. �I need a proven circuit for
>> 0 to 30V DC variable power supply with minimum 2.5 A current
>> output.
>
> If it needs to be 'proven', you need to BUY, not build.
> 30VDC output means at least 33V input, and at low-voltage
> that puts out 33V x 2.5A = 82W, which means a single
> inexpensive transistor isn't gonna handle the output.
For such small power pretty well any cheap bjt or fet in say a
to247,TO-3PN or ISOPLUS247 is fine you'll need two maybe three for
the pass device. Notice I didnt say T0-3 and similiar because
heatsinks are more widely avilable for the other packages. A $20 or
less heatsink should be good enough.Mount them on something like
this
http://canada.newark.com/h-s-marston/43dn-01000-a-200/heat-sink-
extrusion/dp/46WX664.
I was easily dissapateing 120W useing two T0-3PN fets on a heatsink
from a microwave oven with a $5 42CFM fan. The case temp was at
about 90C.The heatsink was less then half the size of the one in the
link.
The only time you are going to dissapate 82W would be in the event
of catastophic failure. The 723 has foldback protection if it fails
the supply should be fused anyway.
> There's a half dozen tricks that will help: the input power
> can be transformer-tap-selected to lower the waste, or
> the pass transistors can be substituted with regulator
> ICs (which have inbuilt thermal limiting and won't burn up),
> or you can use two regulators with different voltage
> ranges, and diode-isolate so they share the output pin.
>
> The easiest thing to do, though, is just to make a brute-force
> DC power supply, and plug it into a Variac when you want to
> adjust it. That works, it's efficient, and the Variac (variable
> autotransformer) comes in handy for lots of other things.
A 160VA or better variac is pretty pricey though and bulky, they are
definetly useful though.
David Eather
The tracking pre-regulator design on the data sheet might (p12)
Bill Bowden
And how much can a 2N3055 dissipate in the same TO-3 package with an
infinite heatsink? Probably depends on ambient temp? You could use a
center tapped xformer to select either full or half voltage input to
reduce heat. There should be some 12VAC (17 volt peak) battery charger
transformers using the SCR idea. I think they use a center taped
transformer so they only need 2 diodes. If you use a bridge and a
switch, you can select 17 volts peak or 34, which should be about
right for an adjustable 30 volt supply. Maybe DigiKey has something
that would work with a center tap?
-Bill
whit3rd
wrote:
> On Oct 18, 10:11 pm, whit3rd <whit...@gmail.com> wrote:
>
> > On Oct 18, 9:53 pm, Bill Bowden <bper...@bowdenshobbycircuits.info>
> > Even with an infinite heatsink, this part cannot (there's a graph
> > in the data sheet) manage 2.5A if the in/out difference gets
> > as high as 25V.
> And how much can a 2N3055 dissipate in the same TO-3 package with an
> infinite heatsink?
Enough power (spec sheet says 115W), but the safe-operating-area
limit for continuous 2.5A output is only 20V, at 25 C (i.e. with
infinite
heat sink in a warm room). That's called the 'second-breakdown'
limit.
It's a good, cheap transistor, but it'll take several in parallel to
do this job,
and/or a series transistor to take some of the voltage-drop burden.
Tim Williams
news:7edbfddf-3b37-461a...@g13g2000yqj.googlegroups.com...
> It's a good ... transistor
A laughable claim!
At least use MJ15001 for starters. 2N3055 is old and should be forgotten.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Hammy
news:i9mv68$udl$1...@news.eternal-september.org:
> "whit3rd" <whi...@gmail.com> wrote in message
> news:7edbfddf-3b37-461a...@g13g2000yqj.googlegroups.
> com...
>> It's a good ... transistor
>
> A laughable claim!
>
> At least use MJ15001 for starters. 2N3055 is old and should be
> forgotten.
>
> Tim
>
Whats wrong with a P-FET. $8 AT Digikey 3 pages of 300W plus
pacakages to choose from.
http://ixdev.ixys.com/DataSheet/DS99986A%28IXTH-T90P10P%29.pdf
IXYS makes a linear line of fets too,nice. ;-)
The next high power regulator I make is going to be N-FETS for the
pass device; much larger selection, cheaper heatsinks with a larger
selection and no stability concerns at least compared to a PFET or
PNP.
Jan Panteltje
<Ha...@hamster.ca> wrote in <Xns9E177ACE1CC4...@69.16.185.250>:
Has anybody mentioned switchers in this thread?
Seems so much 'cooler'.
Hammy
news:i9n445$khl$1...@news.albasani.net:
[snip]
>
> Has anybody mentioned switchers in this thread?
> Seems so much 'cooler'.
>
He wants 0-30 out I've seen variable output flybacks in that power
range but they cant vary that widely.
This one here is 18-24V @85W out.
http://www.onsemi.com/pub/Collateral/DN06038-D.PDF
You could use an SMPS on the front end to step down the line voltge.
That way you can save the size and expense of a 50/60Hz transformer.
Then just use an op-amp based regulator driving a fet pass device on a
brick heatsink for your variable output.
Given the size of some of the higher power 300W plus benchtop power
supplies today they have to be SMPS's at least the front end.
Jan Panteltje
<Ha...@hamster.ca> wrote in <Xns9E177F5E4F53...@69.16.185.250>:
>Jan Panteltje <pNaonSt...@yahoo.com> wrote in
>news:i9n445$khl$1...@news.albasani.net:
>
>[snip]
>>
>> Has anybody mentioned switchers in this thread?
>> Seems so much 'cooler'.
>>
>
>He wants 0-30 out I've seen variable output flybacks in that power
>range but they cant vary that widely.
But my SEPIC can:
http://panteltje.com/panteltje/pic/pwr_pic/
well at least to 24 V, with a bit more input, say 18V it could do 30 I think.
>This one here is 18-24V @85W out.
>
>http://www.onsemi.com/pub/Collateral/DN06038-D.PDF
Yes, nice.
>You could use an SMPS on the front end to step down the line voltge.
>That way you can save the size and expense of a 50/60Hz transformer.
>Then just use an op-amp based regulator driving a fet pass device on a
>brick heatsink for your variable output.
>
>Given the size of some of the higher power 300W plus benchtop power
>supplies today they have to be SMPS's at least the front end.
There actually is an other way, back in the sixties I did a linear
regulator with a thyristor pre-regulator.
That pre-regulator just kept about 5V over the series transistor at all times.
So dissipation was always rather low.
Very simple circuit, one UJT, about 5 transistors,
had current foldback too.
Hammy
> On a sunny day (Wed, 20 Oct 2010 16:31:13 GMT) it happened Hammy
> <Ha...@hamster.ca> wrote in
> <Xns9E177F5E4F53...@69.16.185.250>:
>
>>Jan Panteltje <pNaonSt...@yahoo.com> wrote in
>>news:i9n445$khl$1...@news.albasani.net:
>>
>>[snip]
>>>
>>> Has anybody mentioned switchers in this thread?
>>> Seems so much 'cooler'.
>>>
>>
>>He wants 0-30 out I've seen variable output flybacks in that power
>>range but they cant vary that widely.
>
> But my SEPIC can:
> http://panteltje.com/panteltje/pic/pwr_pic/
> well at least to 24 V, with a bit more input, say 18V it could do
> 30 I think.
Nice project. What is the ripple like?
I see your bench is nice and clean just like mine.;-)
>
>
>>This one here is 18-24V @85W out.
>>
>>http://www.onsemi.com/pub/Collateral/DN06038-D.PDF
>
> Yes, nice.
>
>>You could use an SMPS on the front end to step down the line
>>voltge. That way you can save the size and expense of a 50/60Hz
>>transformer. Then just use an op-amp based regulator driving a fet
>>pass device on a brick heatsink for your variable output.
>>
>>Given the size of some of the higher power 300W plus benchtop
>>power supplies today they have to be SMPS's at least the front
>>end.
>
> There actually is an other way, back in the sixties I did a linear
> regulator with a thyristor pre-regulator.
> That pre-regulator just kept about 5V over the series transistor
> at all times. So dissipation was always rather low.
> Very simple circuit, one UJT, about 5 transistors,
> had current foldback too.
That is the ideal minimze the Vi-Vout difference.The only thing is
you still need that big 50/60Hz transformer. They get really big and
expensive once you get into the 500VA range for say a 300W output.
I've been noticing a lot of the newer variable output benchtop
supplies are now SMPS. I'm guessing they just use the SMPS as a
tracking pre-regulator feed that to an opamp based linear regulator.
Jan Panteltje
<Ha...@hamster.ca> wrote in <Xns9E179C0FB16A...@69.16.185.247>:
>I've been noticing a lot of the newer variable output benchtop
>supplies are now SMPS. I'm guessing they just use the SMPS as a
>tracking pre-regulator feed that to an opamp based linear regulator.
Feed it into a SEPIC?
whit3rd
> "Tim Williams" <tmoran...@charter.net> wrote innews:i9mv68$udl$1...@news.eternal-september.org:
>
> > "whit3rd" <whit...@gmail.com> wrote in message
> >news:7edbfddf-3b37-461a...@g13g2000yqj.googlegroups.
> > com...
> > At least use MJ15001 for starters. 2N3055 is old and should be
> > forgotten.
Yep, a MJ15001 would do the job with one pass element.
> Whats wrong with a P-FET. $8 AT Digikey
2N3055: four for $8; MJ15001: two for $8
Also, to get a low-voltage output (2V at 2.5A) your drive
requirement on that high-side pass PMOS transistor would require
a negative power supply (-10V to be safe) in addition to the
positive one. To use an NMOS, your 30V output would require drive
power 40V or so.
Michael A. Terrell
whit3rd wrote:
>
> On Oct 20, 9:04 am, Hammy <Ha...@hamster.ca> wrote:
> > "Tim Williams" <tmoran...@charter.net> wrote innews:i9mv68$udl$1...@news.eternal-september.org:
> >
> > > "whit3rd" <whit...@gmail.com> wrote in message
> > >news:7edbfddf-3b37-461a...@g13g2000yqj.googlegroups.
> > > com...
>
> > > At least use MJ15001 for starters. 2N3055 is old and should be
> > > forgotten.
>
> Yep, a MJ15001 would do the job with one pass element.
>
> > Whats wrong with a P-FET. $8 AT Digikey
>
> 2N3055: four for $8; MJ15001: two for $8
What if you have hundreds of surplus 2N3055 you got for nothing?
--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
Jim Thompson
<mike.t...@earthlink.net> wrote:
>
>whit3rd wrote:
>>
>> On Oct 20, 9:04 am, Hammy <Ha...@hamster.ca> wrote:
>> > "Tim Williams" <tmoran...@charter.net> wrote innews:i9mv68$udl$1...@news.eternal-september.org:
>> >
>> > > "whit3rd" <whit...@gmail.com> wrote in message
>> > >news:7edbfddf-3b37-461a...@g13g2000yqj.googlegroups.
>> > > com...
>>
>> > > At least use MJ15001 for starters. 2N3055 is old and should be
>> > > forgotten.
>>
>> Yep, a MJ15001 would do the job with one pass element.
>>
>> > Whats wrong with a P-FET. $8 AT Digikey
>>
>> 2N3055: four for $8; MJ15001: two for $8
>
>
> What if you have hundreds of surplus 2N3055 you got for nothing?
I don't have "hundreds" but I have a few that I've had forever ;-)
Hammy
news:1c8a2acd-cb63-4462-9036-bbae582f9ba3
@n13g2000vbn.googlegroups.co
m:
> On Oct 20, 9:04�am, Hammy <Ha...@hamster.ca> wrote:
>> "Tim Williams" <tmoran...@charter.net> wrote
>> innews:i9mv68$udl$1...@news.ete
> rnal-september.org:
>>
>> > "whit3rd" <whit...@gmail.com> wrote in message
>> >news:7edbfddf-3b37-461a-a6b2-57349f82e4c3
@g13g2000yqj.googlegroup
>> >s.
>> > com...
>
>> > At least use MJ15001 for starters. �2N3055 is old and should be
>> > forgotten.
>
> Yep, a MJ15001 would do the job with one pass element.
>
>> Whats wrong with a P-FET. $8 AT Digikey
>
> 2N3055: four for $8; MJ15001: two for $8
>
> Also, to get a low-voltage output (2V at 2.5A) your drive
> requirement on that high-side pass PMOS transistor would require
> a negative power supply (-10V to be safe) in addition to the
> positive one.
How so? The gate voltage is derived from the input voltage not the
output. The drain is connected to the load.
You will need a negative voltage anyways though if you want to get
down to 0V other then into a short.
I did some more looking their are some P-FETS at digikey in 300W or
greater packages at $4.
> To use an NMOS, your 30V output would require
> drive power 40V or so.
Charge pump IC's are cheap you can even use a 555 timer. Granted its
a few more components but it will give better performance and will
give you a much wider selection in pass devices. I think their are
even some integrated highside N-FET LDO controllers out their that
can be used.
Michael A. Terrell
Jim Thompson wrote:
>
> On Wed, 20 Oct 2010 16:41:30 -0400, "Michael A. Terrell"
> <mike.t...@earthlink.net> wrote:
>
> >
> >whit3rd wrote:
> >>
> >> On Oct 20, 9:04 am, Hammy <Ha...@hamster.ca> wrote:
> >> > "Tim Williams" <tmoran...@charter.net> wrote innews:i9mv68$udl$1...@news.eternal-september.org:
> >> >
> >> > > "whit3rd" <whit...@gmail.com> wrote in message
> >> > >news:7edbfddf-3b37-461a...@g13g2000yqj.googlegroups.
> >> > > com...
> >>
> >> > > At least use MJ15001 for starters. 2N3055 is old and should be
> >> > > forgotten.
> >>
> >> Yep, a MJ15001 would do the job with one pass element.
> >>
> >> > Whats wrong with a P-FET. $8 AT Digikey
> >>
> >> 2N3055: four for $8; MJ15001: two for $8
> >
> >
> > What if you have hundreds of surplus 2N3055 you got for nothing?
>
> I don't have "hundreds" but I have a few that I've had forever ;-)
Not all are marked 2N3055 but I've scrapped a lot of linear power
supplies with really odd form factors, or very high currents. Mostly
from old minicomputers. I have seen whole trays of new 2N3055 sell for
less than 25 cents each at a hamfest. The guy had over a hundred trays
of 100. You could get 10 trays for $150, which was 15 cents each.
who where
<mike.t...@earthlink.net> wrote:
>
>Jim Thompson wrote:
>>
>> On Wed, 20 Oct 2010 16:41:30 -0400, "Michael A. Terrell"
>> <mike.t...@earthlink.net> wrote:
>> > What if you have hundreds of surplus 2N3055 you got for nothing?
>>
>> I don't have "hundreds" but I have a few that I've had forever ;-)
>
>
> Not all are marked 2N3055 but I've scrapped a lot of linear power
>supplies with really odd form factors, or very high currents. Mostly
>from old minicomputers. I have seen whole trays of new 2N3055 sell for
>less than 25 cents each at a hamfest. The guy had over a hundred trays
>of 100. You could get 10 trays for $150, which was 15 cents each.
Still overpriced. The Hfe drops off so fast as Ic rises that they are
at best .... useless. No, wait, they might be useful as heater
elements if you have enough drive.
Jim Thompson
Poor baby! I've designed ignition systems (500V NPN's) where Beta was
around 3 at 5A, yet got very accurate performance.
Making do with what you have available separates the men from the boys
:-)
Bill Bowden
wrote:
I've bought a few desk top computer switching power supplies (working)
for a dollar each at swap meets. Nowadays, I can get the whole
computer P4 (Win xP) for $35. Keyboards are a dollar extra.
-Bill
David Eather
The tracking pre-regulator design on the data sheet *will* do the job (p12)
http://www.national.com/ds/LM/LM138.pdf
Michael A. Terrell
Bill Bowden wrote:
>
> On Oct 20, 2:29 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
> wrote:
> > Jim Thompson wrote:
> >
> > > On Wed, 20 Oct 2010 16:41:30 -0400, "Michael A. Terrell"
> > > <mike.terr...@earthlink.net> wrote:
> >
> > > >whit3rd wrote:
> >
> > > >> On Oct 20, 9:04 am, Hammy <Ha...@hamster.ca> wrote:
> > > >> > "Tim Williams" <tmoran...@charter.net> wrote innews:i9mv68$udl$1...@news.eternal-september.org:
> >
> > > >> > > "whit3rd" <whit...@gmail.com> wrote in message
> > > >> > >news:7edbfddf-3b37-461a...@g13g2000yqj.googlegroups.
> > > >> > > com...
> >
> > > >> > > At least use MJ15001 for starters. 2N3055 is old and should be
> > > >> > > forgotten.
> >
> > > >> Yep, a MJ15001 would do the job with one pass element.
> >
> > > >> > Whats wrong with a P-FET. $8 AT Digikey
> >
> > > >> 2N3055: four for $8; MJ15001: two for $8
> >
> > > > What if you have hundreds of surplus 2N3055 you got for nothing?
> >
> > > I don't have "hundreds" but I have a few that I've had forever ;-)
> >
> > Not all are marked 2N3055 but I've scrapped a lot of linear power
> > supplies with really odd form factors, or very high currents. Mostly
> > from old minicomputers. I have seen whole trays of new 2N3055 sell for
> > less than 25 cents each at a hamfest. The guy had over a hundred trays
> > of 100. You could get 10 trays for $150, which was 15 cents each.
>
> for a dollar each at swap meets.
Quite often not wort the dollar. :(
> Nowadays, I can get the whole
> computer P4 (Win xP) for $35.
You pay for them? I pick them up for free.
> Keyboards are a dollar extra.
You pay for keyboards? Can you use 150 or so? How about 75 mice?
Michael A. Terrell
Drop off at DC? They aren't useless unless you don't know shit about
linear power supplies. There were literally millions of linear power
supplies built with 2N3055. A lot of companies made their entire income
from the LM723 & 2N3055.
Bill Bowden
The fan was worth the dollar.
> > Nowadays, I can get the whole
> > computer P4 (Win xP) for $35.
>
> You pay for them? I pick them up for free.
>
> > Keyboards are a dollar extra.
>
> You pay for keyboards? Can you use 150 or so? How about 75 mice?
>
I pay nowadays if I need one. The keyboard I use is dirty, so I'm
debating spending time cleaning the keys, or just throwing it out and
buying another one.
> --
> Politicians should only get paid if the budget is balanced, and there is
> enough left over to pay them.
-Bill
Michael A. Terrell
Not when you have 15 bannana boxes full of old power supplies and
boxes of used fans.
> > > Nowadays, I can get the whole
> > > computer P4 (Win xP) for $35.
> >
> > You pay for them? I pick them up for free.
> >
> > > Keyboards are a dollar extra.
> >
> > You pay for keyboards? Can you use 150 or so? How about 75 mice?
> >
>
> I pay nowadays if I need one. The keyboard I use is dirty, so I'm
> debating spending time cleaning the keys, or just throwing it out and
> buying another one.
Keyboards are easy to clean. Stand it against the wall and spray a
fine mist of household ammonia or Windex. Bet it stand there a few
minutes and spray it again. A few more minutes and spray it with tap
water, or even better, use distilled water. Let it air dry oer night
and it should be as clean as new. I've done hundreds this way.
Tim Williams
> Also, to get a low-voltage output (2V at 2.5A) your drive
> requirement on that high-side pass PMOS transistor would require
> a negative power supply (-10V to be safe) in addition to the
> positive one. To use an NMOS, your 30V output would require drive
> power 40V or so.
Nahh, PFET is an LDO style thing. Annoying to compensate, but that's just
something to do.
Tim Williams
news:X4qdnWfKJKueySLR...@earthlink.com...
> What if you have hundreds of surplus 2N3055 you got for nothing?
Scrap iron is doing good these days. ;-)
Michael A. Terrell
Tim Williams wrote:
>
> "Michael A. Terrell" <mike.t...@earthlink.net> wrote in message
> news:X4qdnWfKJKueySLR...@earthlink.com...
> > What if you have hundreds of surplus 2N3055 you got for nothing?
>
> Scrap iron is doing good these days. ;-)
Iron? These are mostly tinned copper.
who where
<mike.t...@earthlink.net> wrote:
>
>who where wrote:
>>
>> On Wed, 20 Oct 2010 17:29:30 -0400, "Michael A. Terrell"
>> <mike.t...@earthlink.net> wrote:
>>
>> >
>> >Jim Thompson wrote:
>> >>
>> >> On Wed, 20 Oct 2010 16:41:30 -0400, "Michael A. Terrell"
>> >> <mike.t...@earthlink.net> wrote:
>>
>> >> > What if you have hundreds of surplus 2N3055 you got for nothing?
>> >>
>> >> I don't have "hundreds" but I have a few that I've had forever ;-)
>> >
>> >
>> > Not all are marked 2N3055 but I've scrapped a lot of linear power
>> >supplies with really odd form factors, or very high currents. Mostly
>> >from old minicomputers. I have seen whole trays of new 2N3055 sell for
>> >less than 25 cents each at a hamfest. The guy had over a hundred trays
>> >of 100. You could get 10 trays for $150, which was 15 cents each.
>>
>> Still overpriced. The Hfe drops off so fast as Ic rises that they are
>> at best .... useless. No, wait, they might be useful as heater
>> elements if you have enough drive.
>
>
> Drop off at DC? They aren't useless unless you don't know shit about
>linear power supplies. There were literally millions of linear power
>supplies built with 2N3055. A lot of companies made their entire income
>from the LM723 & 2N3055.
Yes, with massive heatsinks covered with huge numbers of 3055's - saw
many of them in mainframe pooter stuff. I've done PSU's with them,
but rapidly grew tired of the heatsink real estate they consumed.
In relation to the O/P topic - but not a solution - I have one PSU I
built with a 723 driving a single PNP TO3 that gives 12A continuous
over 2-15V on a heatsink about 6" x4".
who where
<To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>On Thu, 21 Oct 2010 07:48:41 +0800, who where <no...@home.net> wrote:
>
>>On Wed, 20 Oct 2010 17:29:30 -0400, "Michael A. Terrell"
>><mike.t...@earthlink.net> wrote:
>>
>>>
>>>Jim Thompson wrote:
>>>>
>>>> On Wed, 20 Oct 2010 16:41:30 -0400, "Michael A. Terrell"
>>>> <mike.t...@earthlink.net> wrote:
>>
>>>> > What if you have hundreds of surplus 2N3055 you got for nothing?
>>>>
>>>> I don't have "hundreds" but I have a few that I've had forever ;-)
>>>
>>>
>>> Not all are marked 2N3055 but I've scrapped a lot of linear power
>>>supplies with really odd form factors, or very high currents. Mostly
>>>from old minicomputers. I have seen whole trays of new 2N3055 sell for
>>>less than 25 cents each at a hamfest. The guy had over a hundred trays
>>>of 100. You could get 10 trays for $150, which was 15 cents each.
>>
>>Still overpriced. The Hfe drops off so fast as Ic rises that they are
>>at best .... useless. No, wait, they might be useful as heater
>>elements if you have enough drive.
>
>Poor baby! I've designed ignition systems (500V NPN's) where Beta was
>around 3 at 5A, yet got very accurate performance.
>
>Making do with what you have available separates the men from the boys
>:-)
Indeed. Maybe I was just lucky to not get stuck witha huge stockpile
of them, so I was free to select devices that best suited the task -
and the 3055 rarely got a look in on that basis OR on bang-for-buck.
As always, YMMV.
Tim Williams
>> > What if you have hundreds of surplus 2N3055 you got for nothing?
>>
>> Scrap iron is doing good these days. ;-)
>
> Iron? These are mostly tinned copper.
Even better. I'll pay you 10% over shipping for the whole load. :)
Jim Thompson
I'm talking back when that device was all you had to work with, not
necessarily now.
whit3rd
wrote:
> Tim Williams wrote:
>
> > "Michael A. Terrell" <mike.terr...@earthlink.net> wrote in message
> >news:X4qdnWfKJKueySLR...@earthlink.com...
> > > What if you have hundreds of surplus 2N3055 you got for nothing?
>
> > Scrap iron is doing good these days. ;-)
>
> Iron? These are mostly tinned copper.
My magnet says steel. The copper-slug '3055 items in my
collection are the plastic-package gizmos that don't have
that nice high 200C operating temperature limit.
Michael A. Terrell
Fred Abse wrote:
>
> On Wed, 20 Oct 2010 21:21:43 -0400, Michael A. Terrell wrote:
>
> > Drop off at DC? They aren't useless unless you don't know shit about
> > linear power supplies. There were literally millions of linear power
> > supplies built with 2N3055. A lot of companies made their entire income
> > from the LM723 & 2N3055.
>
> three megs up". Layout was everything, otherwise the only cure was to
> reduce the loop gain and to hell with the degradation in regulation.
>
> Glad to be rid of both devices.
I've worked with 5V 1000A linear supplies built with them that were
rock solid. Of course, that power supply was in a $250,000 piece of
broadcast equipment.
Michael A. Terrell
I built several 5 to 17 volt high curent supplies biult from a 7805
and a bank of surplus 2N3055 about 30 years ago for two way radio repair
benches. Stable and clean. I had to repair a started motor for one of
my service trucks one day. It ran fine on one of those supplies.
Michael A. Terrell
Then yours are newer than mine.
F. Bertolazzi
> Keyboards are easy to clean. Stand it against the wall and spray a
> fine mist of household ammonia or Windex. Bet it stand there a few
> minutes and spray it again. A few more minutes and spray it with tap
> water, or even better, use distilled water. Let it air dry oer night
> and it should be as clean as new. I've done hundreds this way.
Have you ever tried http://tinyurl.com/25kgvxf moist with plain water?
--
Saluti
Michael A. Terrell
The full link:
I use ammonia to remove body oils from the keycaps. How are you
going to use a cleaning cloth to clean between the keys without spending
hours? I can clean a dozen at a time with my method.
Jan Panteltje
Terrell" <mike.t...@earthlink.net> wrote in
<27adnc0CVdTQJFzR...@earthlink.com>:
>
>"F. Bertolazzi" wrote:
>>
>> Michael A. Terrell:
>>
>> > Keyboards are easy to clean. Stand it against the wall and spray a
>> > fine mist of household ammonia or Windex. Bet it stand there a few
>> > minutes and spray it again. A few more minutes and spray it with tap
>> > water, or even better, use distilled water. Let it air dry oer night
>> > and it should be as clean as new. I've done hundreds this way.
>>
>> Have you ever tried http://tinyurl.com/25kgvxf moist with plain water?
>
> The full link:
>
><http://solutions.3m.com/wps/portal/3M/en_US/Marine/Home/Products/Catalog/?PC_7_RJH9U5230GE3E02LECIE20S4K7_nid=7WN0Q227GJbeC8M57V
>BG46gl>
>
> I use ammonia to remove body oils from the keycaps. How are you
>going to use a cleaning cloth to clean between the keys without spending
>hours? I can clean a dozen at a time with my method.
I work much more precise:
ftp://panteltje.com/pub/key_soup_img_1853.jpg
using normal dishwashing detergent.
You have to know where to put them back tough :-)
Jim Thompson
<mike.t...@earthlink.net> wrote:
>
>"F. Bertolazzi" wrote:
>>
>> Michael A. Terrell:
>>
>> > Keyboards are easy to clean. Stand it against the wall and spray a
>> > fine mist of household ammonia or Windex. Bet it stand there a few
>> > minutes and spray it again. A few more minutes and spray it with tap
>> > water, or even better, use distilled water. Let it air dry oer night
>> > and it should be as clean as new. I've done hundreds this way.
>>
>> Have you ever tried http://tinyurl.com/25kgvxf moist with plain water?
>
> The full link:
>
><http://solutions.3m.com/wps/portal/3M/en_US/Marine/Home/Products/Catalog/?PC_7_RJH9U5230GE3E02LECIE20S4K7_nid=7WN0Q227GJbeC8M57VBG46gl>
>
> I use ammonia to remove body oils from the keycaps. How are you
>going to use a cleaning cloth to clean between the keys without spending
>hours? I can clean a dozen at a time with my method.
Denatured alcohol, knocked down with a little water, in a sink,
slosh... slosh... slosh.
Dry in minutes.
F. Bertolazzi
> The full link:
>
> <http://solutions.3m.com/wps/portal/3M/en_US/Marine/Home/Products/Catalog/?PC_7_RJH9U5230GE3E02LECIE20S4K7_nid=7WN0Q227GJbeC8M57VBG46gl>
Useful onli for big, big screens. ;-)
> I use ammonia to remove body oils from the keycaps.
That cloth is incredibly effective with finger grease.
Also very useful if you are victim of friends and colleagues that have the
need of pointing at the screen with oily fingers.
> How are you going to use a cleaning cloth to clean between the keys
> without spending hours? I can clean a dozen at a time with my method.
I only have two keyboards. :-)
--
Saluti
Jan Panteltje
Terrell" <mike.t...@earthlink.net> wrote in
<a5KdnQ4D0tj5IVzR...@earthlink.com>:
> Why remove the keycaps when there is no need?
Did you ever look under the keycaps?
Rich Grise
> "F. Bertolazzi" wrote:
>> Michael A. Terrell:
>>
>> > Keyboards are easy to clean. Stand it against the wall and spray a
>> > fine mist of household ammonia or Windex. Bet it stand there a few
>> > minutes and spray it again. A few more minutes and spray it with tap
>> > water, or even better, use distilled water. Let it air dry oer night
>> > and it should be as clean as new. I've done hundreds this way.
>>
>> Have you ever tried http://tinyurl.com/25kgvxf moist with plain water?
>
> The full link:
>
> <http://solutions.3m.com/wps/portal/3M/en_US/Marine/Home/Products/Catalog/?PC_7_RJH9U5230GE3E02LECIE20S4K7_nid=7WN0Q227GJbeC8M57VBG46gl>
>
> I use ammonia to remove body oils from the keycaps. How are you
> going to use a cleaning cloth to clean between the keys without spending
> hours? I can clean a dozen at a time with my method.
I've used dish soap and a brush with long bristles. Well, first I blow out
the dust and ashes with shop air, then scrub with dish soap, rinse with
clear water, blow dry with shop air, and let it sit for a day. Works
like a champ!
Cheers!
Rich
Michael A. Terrell
No need to, unless you type on the bottoms. :)
Michael A. Terrell
Jim Thompson wrote:
>
> On Fri, 22 Oct 2010 12:18:02 -0400, "Michael A. Terrell"
> <mike.t...@earthlink.net> wrote:
>
> >
> >"F. Bertolazzi" wrote:
> >>
> >> Michael A. Terrell:
> >>
> >> > Keyboards are easy to clean. Stand it against the wall and spray a
> >> > fine mist of household ammonia or Windex. Bet it stand there a few
> >> > minutes and spray it again. A few more minutes and spray it with tap
> >> > water, or even better, use distilled water. Let it air dry oer night
> >> > and it should be as clean as new. I've done hundreds this way.
> >>
> >> Have you ever tried http://tinyurl.com/25kgvxf moist with plain water?
> >
> > The full link:
> >
> ><http://solutions.3m.com/wps/portal/3M/en_US/Marine/Home/Products/Catalog/?PC_7_RJH9U5230GE3E02LECIE20S4K7_nid=7WN0Q227GJbeC8M57VBG46gl>
> >
> > I use ammonia to remove body oils from the keycaps. How are you
> >going to use a cleaning cloth to clean between the keys without spending
> >hours? I can clean a dozen at a time with my method.
>
> Denatured alcohol, knocked down with a little water, in a sink,
> slosh... slosh... slosh.
>
> Dry in minutes.
Ammonia is cheaper, and I can wait overnight. :)
Michael A. Terrell
I have hundreds.
Michael A. Terrell
Why work harder than you have to?
Jan Panteltje
Terrell" <mike.t...@earthlink.net> wrote in
<LMWdnXaONe7MRVzR...@earthlink.com>:
>> >> > I use ammonia to remove body oils from the keycaps. How are you
>> >> >going to use a cleaning cloth to clean between the keys without spending
>> >> >hours? I can clean a dozen at a time with my method.
>> >>
>> >> I work much more precise:
>> >> ftp://panteltje.com/pub/key_soup_img_1853.jpg
>> >> using normal dishwashing detergent.
>> >> You have to know where to put them back tough :-)
>> >
>> >
>> > Why remove the keycaps when there is no need?
>>
>> Did you ever look under the keycaps?
>
>
> No need to, unless you type on the bottoms. :)
Then it is possible your lunch is still there.
:-)
You can actually test this, if your hear that crunching noise whan you press a key.
Rich Grise
> Rich Grise wrote:
>>
>> I've used dish soap and a brush with long bristles. Well, first I blow out
>> the dust and ashes with shop air, then scrub with dish soap, rinse with
>> clear water, blow dry with shop air, and let it sit for a day. Works
>> like a champ!
>
> Why work harder than you have to?
I needed the scrub brush because the keytops were so thick with finger
crud that you couldn't see the letters. I touch-type, so it was no big
deal to me, but one day I had to have everybody come into my office to
set their email password, and they uniformly complained about not being
able to see the keys.
And the brush was definitely less work than popping and cleaning
individual key tops. ;-)
Cheers!
Rich
F. Bertolazzi
> "F. Bertolazzi" wrote:
>> Useful onli [sic. !] for big, big screens. ;-)
>> I only have two keyboards. :-)
>
> I have hundreds.
Bigger and "plentyer". What a guy! ;-)
--
Saluti
Michael A. Terrell
I am a 100% disabled US Army Veteran. The VA has declared that I can
never work again, so I collect & repair computers to give away as a
hobby. I get a lot morre keyboards than I do computers, and very few
are defective so I always have more than I need.
Michael A. Terrell
Don't you have good enough manners not to eat over a keyboard?
Michael A. Terrell
So is the ammonia.
Bill Bowden
wrote:
I used to work for an IT place driving my truck doing pickups/
delivery. When customers would upgrade, we ended up hauling all the
old stuff away and storing it at the office until we had 100 or so
systems, keyboards, mice, printers, etc.
They finally decided to just scrap the stuff and I hauled several
truckloads to the recycle place. I saved 3 systems and took them home
plus a few extra keyboards and mice. But I'm still using a P3 machine
and a dial-up connection.
But on the better investment side, I found a bagfull of 2N110 point
contact transistors from the 1950s at a garage sale for a couple
bucks. I sold one on ebay to some guy in Australia who paid $12 just
for shipping. I only made $2 and haven't tried the second sale yet.
I like to collect small stuff where I can fit a few hundred in a bag.
-Bill
Rich Grise
>
> Rich Grise wrote:
>>
>> On Fri, 22 Oct 2010 14:32:48 -0400, Michael A. Terrell wrote:
>> > Rich Grise wrote:
>> >>
>> >> I've used dish soap and a brush with long bristles. Well, first I blow out
>> >> the dust and ashes with shop air, then scrub with dish soap, rinse with
>> >> clear water, blow dry with shop air, and let it sit for a day. Works
>> >> like a champ!
>> >
>> > Why work harder than you have to?
>>
>> I needed the scrub brush because the keytops were so thick with finger
>> crud that you couldn't see the letters. I touch-type, so it was no big
>> deal to me, but one day I had to have everybody come into my office to
>> set their email password, and they uniformly complained about not being
>> able to see the keys.
>>
>> And the brush was definitely less work than popping and cleaning
>> individual key tops. ;-)
>
>
> So is the ammonia.
:-)
Michael A. Terrell
I do the computers to help people, and for the exercise. :)
Jan Panteltje
Terrell" <mike.t...@earthlink.net> wrote in
<-8KdnZ2iSdJIsF_R...@earthlink.com>:
>> >> > Why remove the keycaps when there is no need?
>> >>
>> >> Did you ever look under the keycaps?
>> >
>> >
>> > No need to, unless you type on the bottoms. :)
>>
>> Then it is possible your lunch is still there.
>> :-)
>> You can actually test this, if your hear that crunching noise whan you press a key.
>
>
> Don't you have good enough manners not to eat over a keyboard?
No
But I clean what I spill.
Bet other's lunches are still present in yours.
My shortest lived keyboard was a 10 guilders (4 $ or so at the time?) new keyboard.
I spilled tea in it in the first 2 minutes.
It had a foil membrane, and the tea got between the layers immediately.
Somehow it no longer made contact after that.
I use a Logitech keyboard these days, many a cup of coffee went into it,
no problem, just take it apart and clean it.
Not the most perfect keys to type, but very good quality keyboard.
Why need so many? This is now about 10 years old and still 100%.
Michael A. Terrell
Jan Panteltje wrote:
>
> On a sunny day (Fri, 22 Oct 2010 20:35:16 -0400) it happened "Michael A.
> Terrell" <mike.t...@earthlink.net> wrote in
> <-8KdnZ2iSdJIsF_R...@earthlink.com>:
>
> >> >> > Why remove the keycaps when there is no need?
> >> >>
> >> >> Did you ever look under the keycaps?
> >> >
> >> >
> >> > No need to, unless you type on the bottoms. :)
> >>
> >> Then it is possible your lunch is still there.
> >> :-)
> >> You can actually test this, if your hear that crunching noise whan you press a key.
> >
> >
> > Don't you have good enough manners not to eat over a keyboard?
>
> No
> But I clean what I spill.
> Bet other's lunches are still present in yours.
How much? I still have new keyboards that are still in sealed boxes.
> My shortest lived keyboard was a 10 guilders (4 $ or so at the time?) new keyboard.
> I spilled tea in it in the first 2 minutes.
> It had a foil membrane, and the tea got between the layers immediately.
> Somehow it no longer made contact after that.
>
> I use a Logitech keyboard these days, many a cup of coffee went into it,
> no problem, just take it apart and clean it.
> Not the most perfect keys to type, but very good quality keyboard.
> Why need so many? This is now about 10 years old and still 100%.
I have had more failures because of doing web design. Bad cords,
worn out switches and the occasion smashed keyboard when someone walks
in with a heavy item and plops it on a keyboard. I've had a few that
start sending random garbage to the computer in the last 15 years.
Warren
news:i9mv68$udl$1...@news.eternal-september.org:
> "whit3rd" <whi...@gmail.com> wrote in message
> news:7edbfddf-3b37-461a...@g13g2000yqj.google
> groups.com...
>> It's a good ... transistor
>
> A laughable claim!
>
> At least use MJ15001 for starters. 2N3055 is old and
> should be forgotten.
>
> Tim
Mouser lists MJ15001 as "End of Life: Scheduled for
obsolescence and will be discontinued by the supplier.".
I suspect that the 2N3055 will still be around still, long
after it is gone. :)
Warren
Phil Allison
"Warren"
> Mouser lists MJ15001 as "End of Life: Scheduled for
> obsolescence and will be discontinued by the supplier.".
** That remark applies to all ON Semi TO3 pack devices - all they are doing
is replacing them with Pb free versions.
The MJ15001G is such a device as is their 2N3055G.
That aside, TO3 packs are definitely getting rare as plastic packs have
virtually taken over in all consumer applications.
Do the Chinese even know what a TO3 pack looks like ??
.... Phil
who where
wrote:
Maybe so, but it's still a poor choice for PSU's. The gain falls off
dramatically at any decent Ic. I wince whenever I see designs with
these devices.