Re: DC relay latching voltage

On 2024-08-23 4:59 a.m., Pimpom wrote:

On 23-08-2024 04:46 pm, piglet wrote:

Pimpom <Pimpom@invalid.invalid> wrote:

A quick question:
Is it reasonable to assume that most small general-purpose DC relays
will not engage at 50% or the rated coil voltage? If not, how about 40%?
(This is *not* about the release voltage).

That roughly fits my observations but I don’t think it can be trusted ,
aging, vibration or temperatures outside room temp could make it pull in
earlier. You might need to characterise the relays you have in mind.

Thanks for the reply. Actually, my calculations indicate that less than
25% of the nominal voltage will appear across the coil for  some tens of
milliseconds when it should be disengaged. This is caused by a decaying
supply voltage, not an inductive spike.

I'd suggest using a power supply at the maximum decay voltage you expect
then bang the relay a bit to see if it will engage. I assume you have
the normal back diode across the coil for clamping the ringing voltage.
You could use the NO contacts in the relay to keep it energized (Hold)
if it momentarily closes during testing.

John :-#)#

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