Re: relay coil inductance

On Tue, 08 Sep 2009 18:59:52 -0700, Archimedes' Lever
<OneBigLever@xxxxxxxxxxxxxxxxxx> wrote:

On Tue, 08 Sep 2009 08:35:45 -0700, John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sun, 06 Sep 2009 20:50:03 -0700, Archimedes' Lever
<OneBigLever@xxxxxxxxxxxxxxxxxx> wrote:

On Sun, 06 Sep 2009 17:04:19 -0700, John Larkin
<jjSNIPlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

On Sun, 6 Sep 2009 16:04:58 -0700 (PDT), MooseFET <kensmith@xxxxxxxxx>
wrote:

On Sep 6, 3:46 pm, Archimedes' Lever <OneBigLe...@xxxxxxxxxxxxxxxxxx>
wrote:
On Sun, 6 Sep 2009 12:23:11 -0700 (PDT), MooseFET <kensm...@xxxxxxxxx>
wrote:



On Sep 6, 10:23 am, Archimedes' Lever <OneBigLe...@xxxxxxxxxxxxxxxxxx>
wrote:
On Sun, 6 Sep 2009 09:09:38 -0700 (PDT), MooseFET <kensm...@xxxxxxxxx>
wrote:

On Sep 5, 1:58 pm, Archimedes' Lever <OneBigLe...@xxxxxxxxxxxxxxxxxx>
wrote:
On Sat, 05 Sep 2009 12:43:20 -0700, Jim Thompson

<To-Email-Use-The-Envelope-I...@xxxxxxxxxxxxxxx> wrote:

Dead-on, Tim!

                                       ...Jim Thompson

  Relay opening time on a mechanical relay is NOT electrically related.

 It is mechanical.  You can slow it down electrically, but there is
nothing you can do that makes the event occur any faster.

A capacitor across the coil makes the contacts open faster.  Try it,
it works.

  You cannot make it open any faster than a non-suppressed version.

Yes you can.  Try it in a real relay and see.  A small value capacitor
will make the contacts open sooner.  I will let you flounder about
trying to come up with why.

That's interesting. I'll have to think about that. But since
AlwaysWrong disagrees, I know it's true.

John

You just got done posting that one could slow it down. In ANY case, the
unsuppressed coil opens the contacts it has faster than any of the
suppressed methods.

One could go a little bit faster than open-circuit unsupressed, but it
wouldn't be worth the considerable trouble. The point is to get rid of
all armature magnetization as fast as possible.

The shunt capacitance thing might just work.

John


Riskier is to find the voltage that closure occurs at on say 50 units.
Just a tad over that threshold voltage is where you want your drivers to
fire at.

Cool. 5% won't pull in at all, and 25% won't pull in when the
temperature goes up.
Great idea.





Then, release will be as immediate as one can physically make it as the
closure plate will detach even before the voltage drops to zero.

In such a case, one could design a "soft release" in the driver pulse
signature that negates any back-emf spike since there is no high slew
rate fall-to-zero stimulus removal, which is the cause of the spike to
begin with.
The soft release will not slow the relay much if at all, because it is
already close to losing its closure.

No. There's a huge pullin-dropout hysteresis that makes your concept
not work.



Perhaps they should design a relay that has a coil to close it, and a
coil to aid in turn off velocity, and soak the back emf as well.

Dual-coil latching relay.

John

.

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