On Sat, 05 Sep 2009 13:45:22 -0700, life imitates life wrote:

On Sat, 05 Sep 2009 14:01:59 -0500, Tim Wescott
wrote:

On Sat, 05 Sep 2009 11:03:51 -0700, life imitates life wrote:

On Sat, 05 Sep 2009 12:48:41 -0500, John Fields
wrote:

On Sat, 05 Sep 2009 09:41:06 -0700, Jim Thompson
wrote:

I haven't done a relay driver circuit for, literally, eons.

Where do I look for reed relays that work on 3.3V supplies with
specications for the coil inductance?

Thanks!

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That's a toughie.

I can't recall ever seeing inductance data on a spec sheet; I think
you'll probably have to go to the manufacturer for that one.

JF

Would not the real question be why would someone concern himself with
the solenoid inductance of a miniature relay? I could see it if it
were huge.

Jim designs custom IC's, so (I assume) he's concerning himself with it
so he can make the output stage of his circuit both economical and
robust. He may even care about making the relay turn off quickly.

It seems like a perfectly valid concern to me, even if the circuit in
question _isn't_ custom -- what if you're powering the relay from logic,
and want to insure fast & safe turn-off?


Turn off can be immediate. The contacts open before the solenoid
completes opening to the gap it was at when off.

That sounds like a bureaucrat's version of "immediate". A relay will
_always_ turn off with some delay, first for the magnetic field to die
down, then for the contacts to physically move.

Even if you don't care about turning off the magnetic field as fast as
possible, if you don't size your snubber circuit right the coil will take
out your output driver when you try to turn off the current.

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www.wescottdesign.com