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From: liz@poppyrecords.invalid.invalid (Liz Tuddenham)
Newsgroups: sci.electronics.design
Subject: Re: programmable circuit breaker
Date: Thu, 6 Mar 2025 19:08:02 +0000
Organization: Poppy Records
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Lasse Langwadt <llc@fonz.dk> wrote:

> On 3/5/25 17:39, john larkin wrote:
> > On Wed, 5 Mar 2025 16:22:21 +0000, liz@poppyrecords.invalid.invalid
> > (Liz Tuddenham) wrote:
> > 
> >> john larkin <jl@650pot.com> wrote:
> >>
> >> [...]
> >>> Maybe I shouldn't diode clamp the relay coils. I'll have to test the
> >>> dropout time.
> >>
> >> Put a resistor in series with the clamp diode, the value can be chosen
> >> to keep the inductive spike just below the maximum allowable voltage and
> >> that will give the fastest turn-off.  By using higher voltage switching
> >> transistors you can have a higher voltage spike and a faster turn-off -
> >> but there is the risk that the spike might be capacitively coupled to
> >> somewhere vulnerable to damage.
> > 
> > Those little mosfets avalanche reliably. The only hazard would be
> > rapid cycling causing too much power dissipation.
> > 
> > The resistor is a good idea. Or clamp to some giant shared TVS zener.
> > 
> 
> or just diode to the 48V supply

As long as the supply can absorb current or is supplying a greater load
current than the relays can dump.


-- 
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk