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From: Don Y <blockedofcourse@foo.invalid>
Newsgroups: sci.electronics.design
Subject: Re: programmable circuit breaker
Date: Wed, 5 Mar 2025 10:50:31 -0700
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On 3/5/2025 9:22 AM, Liz Tuddenham wrote:
> 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.

It's best to put a zener rated for the coil voltage.  This helps
the coil release faster.  A regular diode will slow the opening of
the contacts.

Relays 101