Wouter van Ooijen wrote:
>> If split-second timing is
>> important, remember that the solenoid will energize as quickly as
>> before, but it may hang up for a split-second before releasing.
>
> If timing is important you can use a zener in series with the diode,
> or even a resistor. The voltage at the 'low' side of the coil will be
> higher, so you must decide what the maximum voltage there can be.

Another trick to increase the response time of a relay is to put a parallel
capacitor and resistor in series with the relay coil.  Make sure the time
constant of R*C is less than half or so of the minimum relay on or off time,
then set the R so that the steady state current thru the coil is just the
"holding" current, but not the "pull in" current.  The capacitor initially
allows more current to flow when the relay is switched on, but the current
will fall to a lower level once it has been engaged.  This lower current and
therefore lower magnetic field is quicker to switch off.


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