PWM control of Amperage controlled Proportional Valve

Thread Starter

BobTheBuilder123

Joined Nov 22, 2020
4
We're using 3d printers and looking to do part cooling using compressed air rather than a fan (gives more precise and much more cooling capacity). We're using the Duet controller, which gives PWM control of fan outputs. However, the proportional valve we would like to use takes current control http://www.smcpneumatics.com/assets/images/pdf/PVQ.pdf and it looks like we need to provide something between 120-130mA to 170mA to provide the full range of flow control as we will be operating at ~5psi and below. So... if you have any idea how to solve this problem and happy to help a noob out... I would be super appreciative!
 

Alec_t

Joined Sep 17, 2013
11,794
Welcome to AAC!
What PWM frequency and output signal voltage do you get from the Duet controller?
Will the valve have a 12V or 24V supply?
 

Thread Starter

BobTheBuilder123

Joined Nov 22, 2020
4
Welcome to AAC!
What PWM frequency and output signal voltage do you get from the Duet controller?
Will the valve have a 12V or 24V supply?
Thanks! The fan header output is 2 wire 24v (using the 24Vin input to the Duet board), which I was planning on feeding to the control circuit for the proportional solenoid. The PWM frequency can be configured from the firmware using parameters for the fan control so is variable to need.
https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans
https://duet3d.dozuki.com/Wiki/Gcode#Section_M106_Fan_On
 

Sensacell

Joined Jun 19, 2012
2,671
If you do not need super fast response in the valve, you could simply filter the PWM to a DC voltage and use a simple analog opamp current sink to drive the valve. The only tricky part is managing the power dissipation in the pass transistor, its gonna get hot.
 

strantor

Joined Oct 3, 2010
5,382
You're driving a coil, an inductive load, which should tend to "regulate" a steady current flow through itself naturally. I suspect all you would need is a rectifier diode and a single low-side switch (mosfet or bjt) and directly PWM the valve.
 

eetech00

Joined Jun 8, 2013
2,162

Thread Starter

BobTheBuilder123

Joined Nov 22, 2020
4
Thank you all for the help - it's really helpful. I'm talking with a colleague that has a better understanding of electronics than I do, and will come back with any questions.
 
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