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I am working on a project in which I have to control 3 different proportional solenoid valves. I have never worked with solenoid valves before, at first I thought proportional valves could be controlled with a simple square PWM but I have doubts : is it possible that some valves need a specific controller, or be current controlled?

If we take a look at the datasheet of the 3 valves I need to work with, the way they are controlled is not clear to me :

The first one is 6252AD02L0A00F1, the datasheet is here : https://www.emerson.com/documents/automation/european-catalog-solenoid-valve-general-service-dental-manifold-252-asco-en-6994578.pdf
It is a block of 3 valves, 2 are direct and the last one is proportional. The only information we have is : " Proportional valve (P): 70 – 220 mA (24V) "
Does it mean that it should be controlled in current? How is it generally done?

The second is H226A546S0A00F1, the datasheet is here : https://www.emerson.com/documents/automation/catalog-series-226-miniature-valves-proportional-asco-en-6775570.pdf
There is very little information on the way it should be controlled. Is it possible to deduce it from the datasheet?

The last one is SCG202A204V 24/DC, the datasheet is here : https://cdn.kempstoncontrols.com/files/080ec0fd543b7a0cdbc48608bce58699/SCG202A204V.24/DC.pdf
It is stated : " Voltage regulation 0 - 24 V DC. 24 V DC pulse width modulated (400 Hz) ".
Does it mean that a standard square 400 Hz PWM is enough? If so, why do they propose to use a controller : "E908A003" (datasheet : https://www.emerson.com/documents/automation/european-catalog-electronic-proportional-control-unit-908-asco-en-5044452.pdf) ?

Thanks a lot!

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  • \$\begingroup\$ Coil + PWM + flyback diode = buck converter \$\endgroup\$
    – user253751
    Nov 3, 2021 at 9:43

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They are current controlled with a solenoid drivers, like DRV101 and similar. You can do your own current controller with a current sense shunt/amplifier

The linked data of the valves are misleading and they are not complete. For each spool type, you should also get a diagram flow VS. current. Beside of the current controller loop, usually you also want a ramp generator and dither control.

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  • \$\begingroup\$ So as I understand, it is not enough to drive a proportional solenoid using only this kind of driver ? I was thinking of using this simple circuit : forums.futura-sciences.com/attachments/electronique/… and make the ramp myself using PWM from an MCU... \$\endgroup\$
    – JackOfHearts
    Nov 3, 2021 at 10:10
  • \$\begingroup\$ No. You do need to measure/control current, typically 1200mA @ 100%. Also some protection features are welcome. These days it would be high side MOSFET and high side current sense. I would certainly look for intelligent highside switch up to 2kHz. \$\endgroup\$
    – Marko Buršič
    Nov 3, 2021 at 15:26
  • \$\begingroup\$ You are right, I have been gathering information since I have posted and it seems mandatory to add a current feedback loop using a shunt resistor, which can be sent back to the MCU. I have also learned that proportional valves suffer from hysteresis so the same current will not always yield the same valve position. To reduce this issue, a low-frequency signal (20 Hz) can be added to the PWM to add dither to the signal. The problem is that external driver like the E908A003 can be very expensive... \$\endgroup\$
    – JackOfHearts
    Nov 3, 2021 at 15:39
  • \$\begingroup\$ The industrial electronics is always expensive, but that E908A003 doesn't seem a very valuable piece. It's better to have a DIN rail module and standard connector on the solenoid. TI offers some multichannel half-bridge motor/solenoid drivers. You could make a module for your 3 solenoids with all protections. The MCU has to do current PI control + dither and send PWM pulses. If an emergency stop is needed, then you'd better to split power and control voltage and add Enable signal. If this is a series product, then it worth doing a custom board. \$\endgroup\$
    – Marko Buršič
    Nov 3, 2021 at 18:05

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