On Sun, 13 Sep 2009 18:06:16 +0100, "ian field"
wrote:
"amdx" wrote in message
. ..
"ian field" wrote in message
...
"John Fields" wrote in message
...
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.
---
L di
E= ------,
dt
so the diode damping the "spark" when the driver went open would slow
down the opening of the contacts, maybe?
Or maybe the magnetic field building up and breaking down might affect
some nearby component?
Dunno...
JF
ISTR an appnote floating about on the net that recommends using a
combination of diode and zener to clamp the back emf, apparently if you
just clamp it with a single diode, the back emf drives a current round
the diode/solenoid circuit which causes hesitant unlatching.
Probably this one?
http://www.kilovac.com/appnotes/app_pdfs/13c3311.pdf
Note, life imitates life finds no wisdom in a ten year old document.
That's one of them, there's one that describes using a zener as well as a
back emf diode to prevent shunting the spike current back into the coil and
slowing down de-latching and one appropriately titled for the thread subject
line.
http://www.kilovac.com/appnotes/app_pdfs/13c3264.pdf
http://www.kilovac.com/appnotes/app_pdfs/13c3311.pdf
http://www.kilovac.com/appnotes/app_pdfs/13c3344.pdf
BTW: My A/C contactors have a magnet assembly to pull the arc out of
the contact gap. I understand there are literally contactors that
"blow" the arc away ;-)
...Jim Thompson
--
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