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View Full Version : Total current capability of the ULN2803 chip



Vern Graner
08-09-2005, 07:26 AM
Ok, either I'm not reading the right sheet (http://www.rentron.com/Files/uln2803.pdf), or something.. but I can't seem to find what the total maximum current draw is on the ULN2803a. I know it is mentioned that you can sink 500ma per channel, and there are 8 channels, but does this mean I can sink 500ma per channel on ALL channels at the same time? http://forums.parallax.com/images/smilies/confused.gif

If so, that would mean I'd be passing FOUR AMPS through that little chip. I imagine the trace size on the PROP-1 may play into this equation as well? Anyway, is there a maximum current draw when all channels are driven at the same time? FWIW, I am trying to set up a PROP-1 to control a 24v motor at up to 1amp of current.

Vern

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Vern Graner CNE/CNA/SSE | "If the network is down, then you're
Senior Systems Engineer | obviously incompetent so why are we
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Post Edited (Vern) : 8/8/2005 11:42:15 PM GMT

Newzed
08-09-2005, 07:41 AM
I would suggest you switch tothe TIP120 Darlington transistor.· They will handle 5 amps and cost about $0.55.

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Sid Weaver
Do you have a Stamp Tester yet?
http://hometown.aol.com/newzed/index.html

·

Vern Graner
08-09-2005, 09:10 AM
Newzed said...
I would suggest you switch tothe TIP120 Darlington transistor. They will handle 5 amps and cost about $0.55.


Thats an idea, however, I am planning to use the ParallaxEFX PROP-1 (http://www.parallax.com/detail.asp?product_id=31101) and it already has a socketed ULN2803 on it ready to go... I'd rather use what's there, unless it won't work for this application..?

Vern

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Vern Graner CNE/CNA/SSE | "If the network is down, then you're
Senior Systems Engineer | obviously incompetent so why are we
Texas Information Services | paying you? Of course,if the network
http://www.txis.com | is up, then we obviously don't need
Austin Office 512 328-8947 | you, so why are we paying you?" İVLG

Chris Savage
08-09-2005, 09:13 AM
Sid,

·· The ULN2803 is built on to the Prop-1, so you can't substitute it for TIP120's.· Vern, to answer your question the way I am reading the datasheet you can have all channels driving 350mA X 8 at an appropriate duty cycle.· This also means there's no simple answer as it also talks about ambient temp, cooling, etc.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)