At 02:03 AM 12/7/02 +1100, you wrote:
>Sorry to take the focus away from global warming and
>child aggression, but has anyone done open-loop
>solenoid driving, specifically to make a solenoid
>move SLOWLY by a simple PWM waveform??
>
>I need to make a solenoid either pull-in or drop-out
>(either is ok) but slowly.
>
>Assume a 12v solenoid with a simple spring and about
>6mm of travel. The solenoid armature and load have
>constant mass, spring tension will remain similar
>and friction is within a predictable small range.
>
>Is it feasable to just kill the solenoid current,
>wait a time for the armature to travel small distance,
>then give a short current pulse to halt armature
>movement, then repeat a couple of times? I'm guessing
>that a few correctly timed pulses would give an
>armature release of maybe 0.5 seconds compared to
>the normal release time of <0.1 seconds?

The problem is that the force is a nonlinear function
of the core position. A mechanical dash pot might be
easier. Though your idea is intriguing, I think that
the position would not be predictable enough with
variations in the spring, mass, etc. unless there was
some feedback of core position.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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