Re: programmable circuit breaker

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 ~
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www.poppyrecords.co.uk