Simple PWM Solenoid Driver?

Brianmcm

Is there a simple circuit to allow·the Basic Stamp to control a 12Vdc Solenoid using the PWM command? I understand that using PWM can vary the position of the solenoid plunger.
Any help would be greatly appreciated.

Thank you
Brian.

NoiseMantra

You might want to try something like the attached circuit.
However, solenoids aren't generally designed to actuate over a range of positions,
so it wouldn't surprise me if your solenoid just hummed or buzzed for a while and
then clicked all the way in once your PWM circuit reached a certain threshold.

Put the solenoid in place of the motor
and use a high current transistor,
preferably a darlington such as a TIP120.

Phil Pilgrim (PhiPi)

A Darlington will likely overheat if it's driven with the PWM command. The reason is that Darlingtons switch slowly — probably more slowly than the PWM pulses, which can be a short as 4us. As a consequence, the Darlington will spend a lot of time in its linear region for duty cycles of less than 100%. You can try it, but if the transistor gets too hot, you'll know the reason.

A better choice may be to use a MOSFET, like the IRL520 that Parallax sells.

BTW, I assume from your question that the solenoid has a spring return or some other force to oppose the pull from the coil, right?

-Phil

Brianmcm

Thank you so much for the info. The idea was based on an article I came across that was using the solenoid as part of a Pressure Balance Valve assembly. They article described a pull-in solenoid placed vertically where gravity was the return force. The solenoid is being used to control an air gap. I was intrigued and wanted to experiment.