relay coil inductance

Mouser has a bunch of them. Most have data sheets available. Some of the data sheets even have specs. including inductance, resitance, etc.

I'll have my customer measure one ;-)

...Jim Thompson

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?

Probably, Jim is designing an IC where every 'square' or 'hex' counts. So maybe he doesn't want to use more than he has to? Just a thought.

Jon

What would NymNoNuts know?

I'm working with an X-Fab BiCMOS process... nominally 5.5V max (7V absolute max).

Can't use a "flyback" diode... any "diode" will induce destructive substrate currents.

So I'm using an old design trick of mine from "eons" ago... active device turn-on to limit "flyback".

So I need the inductance to estimate device sizes.

What would NymNoNuts know? Heaven help us, but I estimate he's a technician in our "defense" industry :-( ...Jim Thompson

I suppose it is possible. I doubt much field is generated though.

The collapsing field gets pumped into the diode. One could design the firing circuit to "slow stop" as well. reducing any collapsing flux to minimal since it is created as a result of the slew rate at which it was collapsed.

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

What would a retard that replies the way you do know?

You should not fire them directly from the chip. They should ALL incorporate a driver AFTER the chip for each one. Diodes have been placed across the coils of relays for decades. There is a reason for that. The diode CLAMPS current, keeping it from the driver, idiot!

The flyback occurs at turn off, NOT turn on, idiot, and the diode is ONLY in play during turn off events, and is specifically for clamping that flyback event.

I think you are in overkill mode.

Likely far more than you.

That is another one of your problems. Your capacity to make a valid estimation died twenty years ago, and your capacity to make one in your senile condition is even less than it was when you were not senile. Even then, it was marginal, at best.

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.

Do you think that, with a diode across the relay to reduce the flyback voltage spike, that slow-er decaying current, and its associated magnetic field holding the relay in, does NOT slow down the relay opening ???

boB

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.

NymNoNuts has no CLUE ;-)

...Jim Thompson

"life imitates life"... as defined by yet another persona of NymNoNuts (and caught by my filters)... doesn't have a clue about coil energy that has to go somewhere. ...Jim Thompson

The coil's flux collapses and creates a spike. The diode clamping that spike does NOT slow the spring loaded return time of the plate which is attached to the contact(s) as it pulls away from the solenoid core end face.

So, the answer is NO. The magnetic field is collapsing, as in NOT "holding in" the relay any longer. The plate begins to pull away as soon as the power is removed, and the clamping diode does nothing to slow that process.

The field is collapsing, not being splayed out. There is no longer an attachment force as soon as the power is removed. The collapsing flux induces a current though the diode, but that diode does NOT slow the collapse rate. That rate was determined by the slew rate of the voltage change which was full voltage to zero in a practically square wave fall rate.

The collapsing flux makes the back EMF. The diode eats that current. The plate has already been released long before those events. Diode or not, the relay opens at the same rate. The diode is there to kill the spike, and that is all.

To slow the process, one needs to slow the rate at which the excitation voltage falls. Once it falls below a certain value, however, the relay will STILL "snap" open, so even that method does not "slow" things much.

Speeding one up, however, is what the engineers that designed it did. I doubt you will be able to improve on their works short of adding a solenoid to pull the relay off faster than the mechanical spring does. A push-pull relay where there are two solenoids operating it.

Otherwise, you are simply tied to the mechanics of the system.

Lighting your retarded ass up with a few fibrillation inducing jolts is well within the realm of my knowledge, and proves yet again that you have no clue about that which you spew.

Of course shit is not all that conductive, so I might have to up the juice quite a bit to have an effect on you.

pasticcio