Remote Control Power

Kirk Fraser

I had a bench power supply which could do 0-24VDC at up to 5A which would run a JK-FlipFlop circuit with two IRL530's to power a hydraulic valve to easily slam the valve open and closed at full pressure or less depending on the voltage selected, resulting in a faster or slower hydraulic actuator motion. Setting the power supply to 12V would run it at about half speed. Now I've been trying to automate that manual setting of the power supply using a Prop output of a PWM signal into a TC4427 to drive a pair of IRF3708's. Unfortunately the result has a large drop-out in response between 12 and 24 volts compared to the manual power supply.

Is my best bet to buy 12V coils which may capture the lower response or try to replace TC4427 with something better? Is the problem that my newer fixed voltage 24V 1A power supply not powerful enough at mid-range? I have seen something about an electronic remote control pot on Digi-key. Would it be best to just try to copy the old bench power supply circuit and replace the manual voltage control pot with an electronic pot? If nobody knows directly, any suggestions for a course of action?

Thank you.

kwinn

It is possible your new power supply cannot supply enough current to the valve coil. Another possibility is that with a PWM signal the current through the coil does not reach maximum level during the pulse. The valve coil is an inductor so the current will increase from 0 at a rate determined by the inductance. This means that at at 50% duty cycle the average current through the coil will be less than 50%.

Is this a servo hydraulic valve?

Kirk Fraser

Thanks, that helps. I'll work on applying more power. The valve is called a proportional valve which I think is the same as a servo-valve but it is controlled directly by magnetic coils, not servo-motors.

Toby Seckshund

A long time ago, I looked into a problem that my father had. He was using 24 Volt pneumatic valves and he was only asking for them to be fully open or fully shut but they were gettin very warm/bordering on hot. It turned out that the coils were AC rated and relied on their inductance to cut down on the current, even at 50Hz.