On Sat, 05 Sep 2009 17:54:23 -0500, Tim Wescott
wrote:

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!

---
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".

More ****ing retarded bull**** from someone with no real argument that
is based in fact.

A relay will
_always_ turn off with some delay,

No ****, you retarded ****. It was *I* that said that you can slow the
opening, but will fail to make it faster than it already is.

first for the magnetic field to die
down,

Wrong. The closure plate begins to pull away as soon as the excitation
voltage is removed. A static field pulls in and holds the plate, a
collapsing field does not.

then for the contacts to physically move.

That is a function of how far BEFORE the plate closure point they MAKE
contact. They will always make contact before the plate is fully
clasped. They will always remain in contact as the plate pulls away,
until it reaches a specific point of opening.

Even if you don't care about turning off the magnetic field as fast as
possible,

First it has to matter. Nearly all designers remove excitation voltage
immediately. That means the field is removed immediately. That is also
what causes the spike.

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.

That is what the diode is for. There will be no current any further
back in the circuit if the diode does its job.