How do I control a large motor without my power transistors getting hot as hell?
Jim Rogers
I'm trying to change the speed of a large motor (it came out of an
electric wheelchair). Anyway I have a small NPN BJT that
outputs a voltage between 0 and 24 V. I have an NPN BJ power
transistor with the collector tied to 24V, the base tied to the output
of the smaller transistor, and the emitter connected to one terminal
of the motor, with the other terminal of the motor connected to ground.
The problem I'm having is with the power transitor heating up. How
can I get around this? The transitor is rated with a collector current
of 30 amps, which is over what the motor can draw (resistance across
the terminals is about 1 ohm, so max current = 24V/1 ohm = 24 amps).
I realize I can just put a resistor in there, but this slows the motor
down. Is there another type of transistor configuration I can use that
would be more efficient? How about using the output of the small
transistor to control the pulse width of a square wave? This works
better, but I still have a heat problem at low RPM and I would like
to avoid the extra circuitry for pulsing if possible. Would using
an N-type enhancement MOSFET work better?
Thanks for any advice.
Jim
Reckless
Jim Rogers <ji...@ilinks.net> wrote:
>I'm trying to change the speed of a large motor (it came out of an
>electric wheelchair). Anyway I have a small NPN BJT that
>outputs a voltage between 0 and 24 V. I have an NPN BJ power
>transistor with the collector tied to 24V, the base tied to the output
>of the smaller transistor, and the emitter connected to one terminal
>of the motor, with the other terminal of the motor connected to ground.
>The problem I'm having is with the power transitor heating up. How
>can I get around this? The transitor is rated with a collector current
>of 30 amps, which is over what the motor can draw (resistance across
>the terminals is about 1 ohm, so max current = 24V/1 ohm = 24 amps).
If it's not on a heatsink (the power transistor), it needs to be. The
worst case would be a stall condition which would be 24V @ 24 amps or
576 watts to be dissipated by the transistor. That exceeds the
dissipation capability ot a TO-3 case even if it was on a huge
heatsink.
If you're operating the transistor in linear mode to make the control
electronics "simpler", you have the problem of dissipating the power
not delivered to the load (the motor). At half speed or 12V then
transistor must dump the same amount of power as the motor is using.
The slower the motor is expected to turn, the more voltage across the
transistor. You can also run into torque problems--not enought torque
at low rpms.
Going to PWM will solve most of your problems. Decent torque even at
low speeds, very low losses which will lead to longer battery life.
Going to mosfets, especially some of the high-current low
on-resistance units will make for the most efficient controller.
>I realize I can just put a resistor in there, but this slows the motor
>down. Is there another type of transistor configuration I can use that
>would be more efficient? How about using the output of the small
>transistor to control the pulse width of a square wave? This works
>better, but I still have a heat problem at low RPM and I would like
>to avoid the extra circuitry for pulsing if possible. Would using
>an N-type enhancement MOSFET work better?
>Thanks for any advice.
>Jim
Hope this helps,
Reckless
Eugene Blanchard
>I realize I can just put a resistor in there, but this slows the motor
>down. Is there another type of transistor configuration I can use that
>would be more efficient? How about using the output of the small
>transistor to control the pulse width of a square wave? This works
>better, but I still have a heat problem at low RPM and I would like
>to avoid the extra circuitry for pulsing if possible. Would using
>an N-type enhancement MOSFET work better?
>
If you are interested in MOSFET H-bridges as an alternative check out:
Richard Torrens
In article <329F85...@ilinks.net>, Jim Rogers <ji...@ilinks.net> wrote:
>
> I'm trying to change the speed of a large motor (it came out of an
Have a look at our www site: this type of motor is one of the ones our
controllers are designed for and (even if you don't want to buy a
controller) there is a lot of relevant info there.
A typical wheelchair motor will be rated at 24v 10amps: on stall it could
take 50 amps or more. There are plenty of simple controller circuits
around: and plenty of dead MOSFETs when the circuit didn't behave as
expected!
A suitable controller for this motor is probably not as expensive as you
think: prices are on the site.
--
/| Richard Torrens
/ |
/ | 4 Q D - 4...@argonet.co.uk
/ | |
/ /| | We manufacture
/ / | | MOSFET controllers for battery operated motors
/_/__| |____
/_____ ____\ See us on http://www.argonet.co.uk/users/4qd
/ _ \| | _ \ our www site also contains FAQ sheet on motors & controllers
| | | | | | | | and a selection of interesting circuit diagrams
| |_| | | |_| |
\__\_\ |____/ We use an Acorn StrongARM RISC-PC 32 bit computer.
Tony Hardman
In article <57o8u5$o...@news4.snfc21.pacbell.net>, Reckless <reckless@pac
bell.net.REMOVE.TO.REPLY> writes
>Jim Rogers <ji...@ilinks.net> wrote:
>
>>I'm trying to change the speed of a large motor (it came out of an
>>outputs a voltage between 0 and 24 V. I have an NPN BJ power
>>transistor with the collector tied to 24V, the base tied to the output
>>of the smaller transistor, and the emitter connected to one terminal
>>of the motor, with the other terminal of the motor connected to ground.
>>The problem I'm having is with the power transitor heating up. How
>>can I get around this? The transitor is rated with a collector current
>>of 30 amps, which is over what the motor can draw (resistance across
>>the terminals is about 1 ohm, so max current = 24V/1 ohm = 24 amps).
>
>If it's not on a heatsink (the power transistor), it needs to be. The
>worst case would be a stall condition which would be 24V @ 24 amps or
>576 watts to be dissipated by the transistor. That exceeds the
>dissipation capability ot a TO-3 case even if it was on a huge
>heatsink.
>
motor (1 ohm) looks and acts like a resistor. To got near 24v across it
the on resistance of a FET must be lower, or the forward voltave of the
transistor must be low (say 1 volt of my math). The heat dissipated is
23A * 1v = 23W which is OK (still needs a big heatsink).
The motor will have trouble disipating the other 500W for any time, so I
would consider some type of cut out (thermal, or voltage monitoring).
Sorry about being picky.. (even more sorry if I'm wrong <grin>). I agree
with your other comments completely.
[how fast can one of those wheel chairs go?]
good luck
>If you're operating the transistor in linear mode to make the control
>electronics "simpler", you have the problem of dissipating the power
>not delivered to the load (the motor). At half speed or 12V then
>transistor must dump the same amount of power as the motor is using.
>The slower the motor is expected to turn, the more voltage across the
>transistor. You can also run into torque problems--not enought torque
>at low rpms.
>
>Going to PWM will solve most of your problems. Decent torque even at
>low speeds, very low losses which will lead to longer battery life.
>Going to mosfets, especially some of the high-current low
>on-resistance units will make for the most efficient controller.
>
>>I realize I can just put a resistor in there, but this slows the motor
>>down. Is there another type of transistor configuration I can use that
>>would be more efficient? How about using the output of the small
>>transistor to control the pulse width of a square wave? This works
>>better, but I still have a heat problem at low RPM and I would like
>>to avoid the extra circuitry for pulsing if possible. Would using
>>an N-type enhancement MOSFET work better?
>
>>Thanks for any advice.
>
>>Jim
>
>Hope this helps,
>
>Reckless
>
>
--
Tony Hardman
Reckless
Tony Hardman <to...@f54x19.demon.co.uk> wrote:
>I failed to follow this one.. A stall condition to me means thet the
>motor (1 ohm) looks and acts like a resistor. To got near 24v across it
>the on resistance of a FET must be lower, or the forward voltave of the
>transistor must be low (say 1 volt of my math). The heat dissipated is
>23A * 1v = 23W which is OK (still needs a big heatsink).
Indeed you are correct. My experience with wheelchair motors shows
them at 0.1 ohm to 0.5 ohm. And I was using darlington bipolar
transistors (CE drop 1.2V-1.5V).
>The motor will have trouble disipating the other 500W for any time, so I
>would consider some type of cut out (thermal, or voltage monitoring).
Worst case for the controller would be 50% speed and heavily loaded.
At light loads back EMF reduces the effective voltage across the
motor. In this case you could have 12V at up to 12 amps (depending
upon load of course) with a peak dissipation of 144W. Still a lot.
Go PWM. At 50% power delivered to the load, the only dissipation on
the transistors will be from switching. MOSFETS are definitely the
way to go.
>Sorry about being picky.. (even more sorry if I'm wrong <grin>). I agree
>with your other comments completely.
>[how fast can one of those wheel chairs go?]
FWIW the machine I built would do about 12MPH and weighed about 120
pounds.
PS. another post indicates stall current on a wheelchair motor as high
as 50 amps@24 volts. Would be good to check the resistance of the
motor while turning the shaft. At some points the resistance will be
lower than others. A good way to check stall current is to put 6-12
volts across the motor and lock the rotor. Measure the current. Use
ohm's law to determine the effective resistance of the motor. Don't
try this at full voltage, you could burn up the brushes or windings.
-Reckless
Quentin Lewis
Jim Rogers wrote:
Jim....try looking at:
http://www.west.net/~rondoc/motfaq.html
For some PWM ideas.
-Quentin
Quentin Lewis
Jim Rogers wrote:
>
> I'm trying to change the speed of a large motor (it came out of an
> electric wheelchair). Anyway I have a small NPN BJT that
> outputs a voltage between 0 and 24 V. I have an NPN BJ power
> transistor with the collector tied to 24V, the base tied to the output
> of the smaller transistor, and the emitter connected to one terminal
> of the motor, with the other terminal of the motor connected to ground.
You are running the transistors in linear mode.....so you are dumping
the unused power (not on the motor) across the transistors. This is a
very inefficient way to do business...not only because you need big heat
sinks, but because you are losing so much power in heat.
PWM is the way to go. With eficient transistors, you should be able to
get about 80-90% of the power on the motor at all speeds.
> The problem I'm having is with the power transitor heating up. How
> can I get around this? The transitor is rated with a collector current
> of 30 amps, which is over what the motor can draw (resistance across
> the terminals is about 1 ohm, so max current = 24V/1 ohm = 24 amps).
>
Yes....the problem isn't current, its POWER! If the transistor is
saturated, and drops say 1v, your 30A of current means 30 WATTS! Thats a
pretty heavily heatsinked/cooled TO-3!
Look into simple PWM circuits.....look at small power supply control
chips. Single ship will not only give you the PWM control you need, but
also have the features you need for short circuit protection.
-Quentin
Tim Dicus
Jim Rogers wrote:
>
> I'm trying to change the speed of a large motor (it came out of an
> electric wheelchair). Anyway I have a small NPN BJT that
> outputs a voltage between 0 and 24 V. I have an NPN BJ power
> transistor with the collector tied to 24V, the base tied to the output
> of the smaller transistor, and the emitter connected to one terminal
> of the motor, with the other terminal of the motor connected to ground.
> can I get around this? The transitor is rated with a collector current
> of 30 amps, which is over what the motor can draw (resistance across
> the terminals is about 1 ohm, so max current = 24V/1 ohm = 24 amps).
>
> down. Is there another type of transistor configuration I can use that
> would be more efficient? How about using the output of the small
> transistor to control the pulse width of a square wave? This works
> better, but I still have a heat problem at low RPM and I would like
> to avoid the extra circuitry for pulsing if possible. Would using
> an N-type enhancement MOSFET work better?
>
> Thanks for any advice.
>
> Jim
Greetings from Destin, Florida!
If you are not going to use PWM, you are going to generate some serious
heat here.
Using a mosfet or IGBT or whatever, will not change the fact that if you
are going to use a transistor-type device as a voltage divider, you have
to deal with two formulas:
E=IR
P=IE
The bad part is not going to happen when the motor is "ON", but at
"HALF". If you drop the voltage across the motor to 12 volts (still one
ohm), current is 12 amps, heat is 144 watts on the motor. The voltage
drop across the transistor (virtually regardless of type) is also 12
volts at 12 amps. Heat developed in the transistor? 144 watts! Half your
power is being used to control the power.
If you use the transistor as a common-emitter, you can normally reduce
the voltage drop across the junction to less than .6 volts, which is as
good as you can do with common-collector. Just the .6 volt drop at 24
amps is going to generate over 14 watts.
The thing that mosfets and IGBTs will do for you over transistors is
lower the junction resistance, so when used in PWM circuits, they
generate relatively little heat.
My recommendation, mosfet International Rectifier IRLZ44, very small
capacitor to control flyback, and PWM. Oh, yes, and a heat sink!
Hope that helps.
See ya!
--
Tim
Destin, Florida
e-mail timo...@gnt.net
Brett Collins
Jim Rogers <ji...@ilinks.net> wrote:
>I'm trying to change the speed of a large motor (it came out of an
>electric wheelchair). Anyway I have a small NPN BJT that
>outputs a voltage between 0 and 24 V. I have an NPN BJ power
>transistor with the collector tied to 24V, the base tied to the output
>of the smaller transistor, and the emitter connected to one terminal
>of the motor, with the other terminal of the motor connected to ground.
>The problem I'm having is with the power transitor heating up. How
>can I get around this? The transitor is rated with a collector current
>of 30 amps, which is over what the motor can draw (resistance across
>the terminals is about 1 ohm, so max current = 24V/1 ohm = 24 amps).
Hi Jim,
The reason your transistor is getting so hot is because of the
voltage drop across it. For example, lets say your circuit is powered
by a 24 volt battery. Your circuit then supplies the motor with lets
say 15 volts at 5 amps. 24 minus 15 yields a voltage drop of 9 volts
across your transistor at 5 amps. 9 volts multiplied by 5 amps gives
us 45 watts that the transistor must dissipate in heat. (E * I = P)
This is why it gets HOT.
Find out what the Pd (power dissipation rating) is for your
transistor. If the Pd is say 130 watts, then figure half that to be
kinda safe.(I said just kinda safe guys, no flames)
It is common to parallel transistors to pass a heavy load for
dissipation limitation reasons. Be sure to use an adequate heatsink.
>I realize I can just put a resistor in there, but this slows the motor
>down. Is there another type of transistor configuration I can use that
>would be more efficient? How about using the output of the small
>transistor to control the pulse width of a square wave? This works
>better, but I still have a heat problem at low RPM and I would like
>to avoid the extra circuitry for pulsing if possible. Would using
>an N-type enhancement MOSFET work better?
Not clear on what you mean when you say using the output of a
transistor to control the width. I haven't built a PWM circuit yet.
If I remember right, you could take a 556 dual timer chip. Configure
first timer as a multivibrator to drive the second timer which would
configured as a one shot. The output of all this drives a mosfet.
If this doesn't work I'm sure someone will say so.
Later,
Brett
Terry King
Quentin Lewis wrote:
>
> Jim Rogers wrote:
> >
> > I'm trying to change the speed of a large motor (it came out of an
25 years ago I built a backyard electric car for my kids using a 6V
generator as a motor; last year I rebuilt that car using an electric
wheelchair (Electric Mobility) motor and transaxle.
I used two MOSFETS (about $4 each) in parallel and a switchmode
Pulsewidth Modulated controller controlled by a pot with a footpedal.
The control is very fine; the Grandchildren can move slowly out of the
garage without hitting anything, or spin the wheels on the dirt driveway.
I used an LM339 Comparator and two 555's: one as the oscillator with
a triangle wave output(constant frequency about 10Khz) and another
555 as the FET Gate driver (it was available and switches the gate
capacitance FAST). There's a 12V regulator to run the control stuff
off the raw 24v gelcels that power everything. Oh yeah, the transaxle has
an electric brake and I used a couple lm339 comparator sections for a
timer and to sense the throttle just coming off 'stop' to release the
brake.
Answer back here if you decide this is something you might want to do.
The schematic is hand-drawn in a notebook at home... It was cheap!
--
Regards, Terry King ...Second House After the Covered Bridge in
Vermont
Bob Wilson
Terry King (tk...@together.net) wrote:
Finally a post from someone who solved the problem by understanding
basic principles, instead of using a specific (and probably expensive
and hard to get) chip to make up for lack of understanding of the
basics. Good work.
Bob.
Terry King
Bob Wilson wrote:
>
> Terry King (tk...@together.net) wrote:
> : Quentin Lewis wrote:
> : >
> : > Jim Rogers wrote:
> : > >
> : > > I'm trying to change the speed of a large motor (it came out of an
> : > > electric wheelchair). Anyway I have a small NPN BJT that...
>
> : 25 years ago I built a backyard electric car for my kids using a 6V
> : generator as a motor; last year I rebuilt that car using an electric
> : wheelchair (Electric Mobility) motor and transaxle.
thread, but before I do something Newbie-Stupid:
-- What are common (even good?) ways of posting schematics on the
electronics newslists?? Right now all I probably have available
is scanned-to-TIFF file. Hmm..
Maybe I better start putting more schematics in electronic form. I have
ORCAD. Can put out PostScript and ZIP it I guess.
I don't want to revisit this too much if it's been discussed but I expect
to hang around here for a long time, and would like to get some of this
stuff figured out so I can contribute as well as ask for help...
Alan Schneider
Terry King <tk...@together.net> wrote:
_>OK; I've had a number of requests for the schematic. I know this is off-
_>thread, but before I do something Newbie-Stupid:
_> -- What are common (even good?) ways of posting schematics on the
_> electronics newslists?? Right now all I probably have available
_> is scanned-to-TIFF file. Hmm..
_>Maybe I better start putting more schematics in electronic form. I have
_>ORCAD. Can put out PostScript and ZIP it I guess.
_>I don't want to revisit this too much if it's been discussed but I expect
_>to hang around here for a long time, and would like to get some of this
_>stuff figured out so I can contribute as well as ask for help...
There is no good way to _post_ schematics to non-graphics
newsgroups. If you do have schematics which you want to
contribute to the group the best way is to set up a web site
(get the details on how to from your ISP), convert the schematics
to GIF format, link them into your web page(s) and then mention
the URL in your posts. That way anyone who is interested can
browse to your web pages and get the circuits and you don't
abuse the newsgroup (and get flamed for it, or worse).
GIF is probably the best graphics format to use as 1) almost
anyone can view it, 2) something like a schematic diagram
compresses very well, 3) it is not *TOO* lossy.
Don't try JPEG - it's hopeless if you're trying to transmit fine
detail and almost certainly won't compress as well as GIF for
this sort of material.
Cheers,
Alan
======================================================
Quantum Mechanics: The Dreams that Stuff is made of.
- Michael Sinz
======================================================
Tim Dicus
Terry King wrote:
>
> Bob Wilson wrote:
> >
> > Terry King (tk...@together.net) wrote:
> > : Quentin Lewis wrote:
> > : >
> > : > Jim Rogers wrote:
> > : > >
> > : > > I'm trying to change the speed of a large motor (it came out of an
> > : > > electric wheelchair). Anyway I have a small NPN BJT that...
> >
> > : 25 years ago I built a backyard electric car for my kids using a 6V
> > : generator as a motor; last year I rebuilt that car using an electric
> > : wheelchair (Electric Mobility) motor and transaxle.
>
> Maybe I better start putting more schematics in electronic form. I have
>
Greetings from Destin, Florida!
Use the smallest graphic you can get away with.
I use .GIF interlaced format for schematics. I draw them with Microsoft
Paint (comes with Windows95), and save them in 16 color (4 bit) format.
Convert to .GIF with Paint Shop Pro (from JASC). Shareware you can
download from the net.
Check the size of the finished picture. If it's larger than 20K, then you
should probably put it on your web page, place a URL in your document,
and let those who wish to see it do so.
Try not to send schematics as attachments unless words can't do it
properly. They kinda clog up the system if too many get into the system
at one time, so don't send one with every post.
Watch for awhile. You'll catch on.
Tim Theis
> -- What are common (even good?) ways of posting schematics on the
> electronics newslists?? Right now all I probably have available
> is scanned-to-TIFF file. Hmm..
>
> Maybe I better start putting more schematics in electronic form. I have
> ORCAD. Can put out PostScript and ZIP it I guess.
>
> I don't want to revisit this too much if it's been discussed but I expect
> to hang around here for a long time, and would like to get some of this
> stuff figured out so I can contribute as well as ask for help...
>
One way that a lot of electronic manufacturers are using for their catalogs
is using the Adobe Acrobat file format. The client is available for free
downloading that will make your web browser Acrobat File compatible (.pdf).
See http://www.adobe.com/acrobat. This is really pretty slick. However I
think the program to generate .pdf files is not free.
Marc
"Tim Theis" <tth...@mail.veda.com> wrote:
For small schematics I capture image from PSpice Eval version and convert to jpg
using microsoft imager. See example for 6N138 I just posted as a response. My
news reader, Free Agent, has a built in UUencoder/decoder so just a button press
and I can upload an UUencoded image and decode a UUencoded post.
Douglas P. McNutt
In Article <01bbe941$61a526e0$b9708ece@Garfield>, "Tim Theis"
<tth...@mail.veda.com> wrote:
>> -- What are common (even good?) ways of posting schematics on the
>> electronics newslists?? Right now all I probably have available
>> is scanned-to-TIFF file. Hmm..
>think the program to generate .pdf files is not free.
>
Distiller. Each will allow you to "print" from an application to a .pdf
file. They also have an option to create a file in 7 bit format which can be
sent over the net without UUencoding or the like.
I have a couple of sample schematics on
ftp://ftp.csn.net/macnauchtan/
The circuitry may not be so good, but the .pdf files are neat.
The problem is that it's difficult to sketch an answer to someone's problem
without going to a drawing program. What we really need is a quickie
blackboard program. Donno how but willing to work on it.
-> From the USA. The only socialist country that refuses to admit it. <-
John Lundgren
If you post a binary larger than 100k total (all sections) to a
non-binary newsgroup, the CANCELBOT will get it, and it will disappear,
and in its place will be a warning message. It's happened here recently.
Marc (mar...@li.net) wrote:
: "Tim Theis" <tth...@mail.veda.com> wrote:
: >> -- What are common (even good?) ways of posting schematics on the
: >> electronics newslists?? Right now all I probably have available
: >> is scanned-to-TIFF file. Hmm..
: >>
: >> Maybe I better start putting more schematics in electronic form. I have
: >> ORCAD. Can put out PostScript and ZIP it I guess.
: >>
: >> I don't want to revisit this too much if it's been discussed but I expect
: >> to hang around here for a long time, and would like to get some of this
: >> stuff figured out so I can contribute as well as ask for help...
: >>
: >One way that a lot of electronic manufacturers are using for their catalogs
: >is using the Adobe Acrobat file format. The client is available for free
: >downloading that will make your web browser Acrobat File compatible (.pdf).
: >See http://www.adobe.com/acrobat. This is really pretty slick. However I
: >think the program to generate .pdf files is not free.
: For small schematics I capture image from PSpice Eval version and convert to jpg
: using microsoft imager. See example for 6N138 I just posted as a response. My
: news reader, Free Agent, has a built in UUencoder/decoder so just a button press
: and I can upload an UUencoded image and decode a UUencoded post.
: Marc
: http://www.li.net/~marcsf
--
#===================================================================#
| John Lundgren - Elec Tech - Info Tech Svcs. | jlundgre@ |
| Rancho Santiago Community College District | deltanet.com |
| 17th St at Bristol \ Santa Ana, CA 92706 | http://www.rancho|
| My opinions are my own, and not my employer's. | .cc.ca.us |
| Most FAQs are available through Thomas Fine's WWW FAQ archive: |
|http://www.cis.ohio-state.edu:80/hypertext/faq/usenet/FAQ-List.html|
| "Babe Ruth struck out 1,330 times... keep on swinging." |
| says the lid on the jar of Laredo & Lefty's Picante Salsa |
! You MAY NOT use my email address for unsolicited Email or lists! !
#======P=G=P==k=e=y==a=v=a=i=l=a=b=l=e==u=p=o=n==r=e=q=u=e=s=t======#
Mark Zenier
: Tim Theis (tth...@mail.veda.com) wrote:
: > -- What are common (even good?) ways of posting schematics on the
: > electronics newslists?? Right now all I probably have available
: > is scanned-to-TIFF file. Hmm..
: >
: > Maybe I better start putting more schematics in electronic form. I have
: > ORCAD. Can put out PostScript and ZIP it I guess.
: >
: > I don't want to revisit this too much if it's been discussed but I expect
: > to hang around here for a long time, and would like to get some of this
: > stuff figured out so I can contribute as well as ask for help...
Read the Q&A section of the "Guide to the sci.electronics newsgroups"
FAQ that just got it's (roughly) regular monthly posting.
To summarize, the lower the common denominator the better. (Remember,
you want the maximum number of people to be able to see it. If you
don't, then email it.) Small (under 30k) encoded files are the
consensus. (Stuff over 30k gets you a copy of the FAQ in your mailbox,
unless the Bincancler ate it first.) Most people seem to get by under
10k char. GIFs seem to get the fewest complaints. (As opposed to
postscript or .pdf). Small pictures, black and white (two color).
Anything over 100k char will trigger the Bincancel system that will
send out a control message to cancel it worldwide. That means bitmaps
(.bmp) are a waste of your time, unless compressed.
Resist the urge to send pictures of some unknown widget. If it's got
numbers on it, the numbers are more useful than a blurry picture where
all you can say is "Yup, that's a 6 pin widget, all right".
Mark Zenier mze...@eskimo.com mze...@netcom.com
John Eaton
Douglas P. McNutt (dmc...@macnauchtan.com) wrote:
: >One way that a lot of electronic manufacturers are using for their catalogs
: >is using the Adobe Acrobat file format. This is really pretty slick. However I
: >think the program to generate .pdf files is not free.
: >
: You need Acrobat Exchange, circa $100, or it's higher priced cousin Acrobat
: Distiller. Each will allow you to "print" from an application to a .pdf
: file. They also have an option to create a file in 7 bit format which can be
: sent over the net without UUencoding or the like.
: I have a couple of sample schematics on
: ftp://ftp.csn.net/macnauchtan/
: The circuitry may not be so good, but the .pdf files are neat.
Local egghead surplus outlet is selling Acrobat exchange 2.1 for $29.95. I do
see more and more vendors supplying data sheets and manuals in pdf form and
find it easier and better than all those stupid hypertext viewers. If I don't
like the viewer then I can at least print off a decent looking manual.
John Eaton
dave anderson
John Lundgren (jlun...@delta1.deltanet.com) wrote:
: If you post a binary larger than 100k total (all sections) to a
: and in its place will be a warning message. It's happened here recently.
Amother plug for HPGL, vector drawings are a lot smaller then bitmaps.
--
dav...@li.net Triak #35 "Eleven" Happiness is flying an ama.
Michael Warner
Under the influence of mind-altering drugs, ala...@zip.com.au suggests...
>GIF is probably the best graphics format to use as 1) almost
>anyone can view it, 2) something like a schematic diagram
>compresses very well, 3) it is not *TOO* lossy.
How about PDF? I imagine most people have the reader by now, and I picked
up the writer (Exchange) from Linear Technology's CD, so I guess that
version at least is free. They're vector-based rather than bitmaps, so
they display and print ideally (in theory) on any device.
GIF is a non-lossy compression.
LOUIS L JR
For black and white (or any solid colors,) gif will give you the best
quality at the smallest file size. For "natural" images (a picture of a
dog for instance,) jpeg will give you the smallest file size at any given
quality.
John Lundgren
Mark Zenier (mze...@netcom.com) wrote:
: : Tim Theis (tth...@mail.veda.com) wrote:
: : > -- What are common (even good?) ways of posting schematics on the
: : > electronics newslists?? Right now all I probably have available
: : > is scanned-to-TIFF file. Hmm..
: : >
: : > Maybe I better start putting more schematics in electronic form. I have
: : > ORCAD. Can put out PostScript and ZIP it I guess.
: : >
: : > I don't want to revisit this too much if it's been discussed but I expect
: : > to hang around here for a long time, and would like to get some of this
: : > stuff figured out so I can contribute as well as ask for help...
: Read the Q&A section of the "Guide to the sci.electronics newsgroups"
: FAQ that just got it's (roughly) regular monthly posting.
: To summarize, the lower the common denominator the better. (Remember,
: you want the maximum number of people to be able to see it. If you
: don't, then email it.) Small (under 30k) encoded files are the
: consensus. (Stuff over 30k gets you a copy of the FAQ in your mailbox,
: unless the Bincancler ate it first.)
I haven't got that yet. Who sends that out? Another automaton? (mailbot)
Most people seem to get by under
: 10k char. GIFs seem to get the fewest complaints. (As opposed to
: postscript or .pdf). Small pictures, black and white (two color).
: Anything over 100k char will trigger the Bincancel system that will
: send out a control message to cancel it worldwide. That means bitmaps
: (.bmp) are a waste of your time, unless compressed.
: Resist the urge to send pictures of some unknown widget. If it's got
: numbers on it, the numbers are more useful than a blurry picture where
: all you can say is "Yup, that's a 6 pin widget, all right".
: Mark Zenier mze...@eskimo.com mze...@netcom.com