I'm designing a controller for a bidirectional proportional valve. The datasheet says to drive with between 40 and 70 Hz 55Hz being ideal. I assume this is due to the low resonant frequency such coils are likely to have.
Is there anything ready made out there chip wise? I could use a H bridge device with current limit driven at 55 Hz. aim for the approximate PWM duty required or simply run at 90% and let the current limit handle it.
Or I could drive a MOSFET to drive the coil with a back EMF diode and have a shut resistor inline with the coil to measure the current. I can quickly figure out the coil resistance and use that to make a best stab at the correct PWM duty before making finer adjustments. Speed is not a concern and accuracy does not have to be high.
If this is for air pressure control, I prefer the 0-10V or 4-20mA proportional valves, like norgren vp50/51.
Remember to consider what you want to happen if the power fails - do you want the PV output to hold or drop. Sometimes has safety implications.
This is a hydraulic valve, each coil takes up to 1.3A to adjust the valve. I'm thinking a single MOSFET per coil with back EMF diode and a current shunt
A MOSFET and freewheel diode is commonly used. With the few I have done, I used a current mode SMPS IC like UC3843 so that increasing solenoid resistance with temperature has little effect on current. With current mode, subharmonic oscillation can be a problem, not in my case because the supply was always 28V driving 12V solenoids, so duty-cycle never exceeded 50%.
Yes I'm going with the MOSFET and freewheeling diode. I was considering a constant current source SM converter using an LED driver but it defaults to full on so gave up and went with the PWM control method. I've got a micro-controller in the thing for CAN bus communication so can monitor and adjust with that.
I'm designing a controller for a bidirectional proportional valve. The datasheet says to drive with between 40 and 70 Hz 55Hz being ideal. I assume this is due to the low resonant frequency such coils are likely to have.
Do you have a link to the actual valve?
This is all the information I have.