Electronics > Projects, Designs, and Technical Stuff
How to pick a transistor to switch a relay
TomS_:
Thanks everyone. Much to go over when I have some more time (something to do on the commute over the coming week, since I'll be stuck on a train instead of riding my motorbike as usual), but it would seem the general consensus at this point that I should ditch the BC547's and probably replace them with some BC337's.
sam[PS]:
Might be off topic here but might not :
If you have more than one relay to drive on the same board consider using a ULN2003 or similar, it's not a transistor it's an ic, but it's special purpose for that application, it doesn't cost much, can drive up to 8 relay and need no other external component (even flyback diode is already in there)...
Just my 2cts...
TomS_:
Interesting idea.
I've only got to control two relays, so for now I reckon these transistors will do the trick.
graybeard:
I have used an ULN2803A in many designs to drive relays. It has the transient suppressor diodes built in.
http://www.ti.com/lit/ds/symlink/uln2803a.pdf
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