Using PWM for valve control
RichardF
Posts: 168
Do you think PWM will work to throttle operate a normally closed solenoid valve? I have an application where I want to control valve position so as to regulate a stream of fluid.
Thanks,
Richard
Thanks,
Richard
Comments
That's how purpose-built hydraulic and other fluid valves work. The big difference is they have been optimized for low inertia, minimum stiction, and fast response. Many are designed just like a speaker coil as opposed to a traditional winding.
If you do some tests with your valve, you can determine how fast it can cycle. (for a standard valve, I'm guessing a small valve might be able to open and close 2 or 3 times a second) Depending on your ultimate use, that might be sufficient.
Cheers,
Thanks, Tom. I will give it a try. What would be a good transistor to use for a buffer between the valve and my Stamp? Valve has a 12 volt solenoid drawing 1/2 amp. Anything come to mind?
Richard
I believe you success will be quite dependent on the type of valve. You say "normally closed", and that could very well be like the fill valves on washing machines and diswashers, and those are "snap action" valves. I believe you will have difficulty in making those operate in any kind of proportional manner. Other valve designs are meant for proportional control, and othersyet, such as the slow acting zone ball valves for hydronic heating systems (typically 24 VAC) could be faked into operating somewhat linearly. As Tom said, do some experimenting with the intended valve, but I predict that the snap action types will cycle from full on to full of, and you might not want a pulsing kind of flow.
Just sayin'.
Cheers
Peter (pjv)
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The duty cycle of the solenoid is usually very low, It will wear out very fast.
....
People often assume PWM means some KHz speed wave , often for DC motors it is ..
But in real .. There is no reason not to declare A Frame of 10 Sec and PWM off that as a number .
it will be ROUGH but In the end you are still doing """ PWM"""""" ..
I do the Same thing with my E Bike . I pulse the bike to get it going .. Human PWM ..
to the OP.. Look at how fast your valve can switch .. . Consider Hoses after it as a Snubber to make the flow not so pulsy.
I can see a 2 Sec Window as your PWM base to work with .
Peter..
I agree. You had better check the specs on whatever valve you are using. Many regular valves have limited cycle life and you can burn through that lifetime pretty fast if you're cycling several times a second.
Richard
P.S. This is a "dancing waters" project.
Might be simpler to replace the solenoid with a proportional valve.