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I am trying to build a servo-controlled water valve. Max pressure 150 psi , valve size 1/2".

Can anyone recommend a suitable 1/4-turn valve, either ceramic, ball valve, or anything else that is easy to turn, even under pressure? It must require very little torque to turn, so a standard servo can rotate it with a small lever attached.

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    $\begingroup$ What's your application? I'm not sure something like an RC servo is the right solution here. Are you familiar with solenoid valves? $\endgroup$ – Guy Sirton Aug 31 '14 at 23:41
  • $\begingroup$ Application is controlling water flow, so a solenoid (on/off only) is not suitable. I need to be able to partially open/close the valve to allow various flow rates. Thanks! $\endgroup$ – Ryan Griggs Sep 1 '14 at 11:10
  • $\begingroup$ There are commercial units available, very expensive. I am trying to build my own for a low cost application. $\endgroup$ – Ryan Griggs Sep 1 '14 at 11:12
  • $\begingroup$ It looks like what i want is called a 'proportional valve' as per electronics.stackexchange.com/questions/60370/… $\endgroup$ – Ryan Griggs Sep 1 '14 at 11:21
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    $\begingroup$ If you have feedback you may be able to modulate (e.g. PWM) an on-off valve to get the flow you need... $\endgroup$ – Guy Sirton Sep 1 '14 at 18:45
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It is pretty common to take a simple and cheap solenoid valve and use a PWM at the input

TI has a pretty nice driver (DRV102) which uses a analog input and provides enough power to switch the most valves. I don't even need a MCU, just a variable resistor is enought Then just take a cheap valve and the job is done

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  • $\begingroup$ Very interesting. Does the liquid exit the line in visible pulses? $\endgroup$ – Ryan Griggs Sep 4 '14 at 10:48
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    $\begingroup$ The used PWM is about 24kHz You cannot see any pulses the piston in the valve is just kept in a middle position proportinal to the duty cycle of the pwm $\endgroup$ – TobiasK Sep 4 '14 at 11:30
  • $\begingroup$ This is exactly the info i was looking for. I did not know solenoid valves could use PWM to partially open. I assumed the valve would pulse open and closed, causing choppy water output. Thank you! $\endgroup$ – Ryan Griggs Sep 5 '14 at 1:50

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