NPN transistor array IC

Thread Starter

BReeves

Joined Nov 24, 2012
410
I thought this would be easy but Google wasn't much help.

I need to drive 7 relays from a micro with 5 volt outputs (Teensy 2.0). I'm driving 4 now with discreet 2n3904 transistors but need a smaller foot print. Was thinking it would be pretty easy to find a through hole IC that consisted of several NPN transistors which would take up less board space than 7 2n3904 transistors and associated resistors.

Looking for ideas from you guys on what I might use to drive the relays?
Thanks
 

ScottWang

Joined Aug 23, 2012
6,926
For a uln2003 or uln2004, the output current whatever for each pin or total is 500 mA, but considering the package and power consumption, using the current less 1/3(500 mA) is better.
 

Thread Starter

BReeves

Joined Nov 24, 2012
410
Just discovered I already have several ULN2803's in my collection. Looks to be the same basic configuration as the 2003. Not sure how I ended up with them but they will sure solve the problem.

Only one relay, maybe two is ever active at any given time and then only for milliseconds. If I use 5 volt DIP relays the coil current is only 40ma, current draw shouldn't be an issue.

Cool, sometimes things just work out...
 
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