Hello friends,
I'm scheming on a way to control proportional valves with a Labjack U3. Using the LJTick-DAC to get two analog channels controlling 0-10VDC seems easy, but the current requirement of each valve is 190mA, which is too much for the Labjack. Is it reasonable to think I could build a simple op-amp buffer circuit between the LJTick-DAC and each valve to get the current I need?
Thank you!
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Getting a high current variable voltage is a problem. As you describe, you could make an op-amp buffer, but you are going to have to provide expanded power rails for the op-amp and will have limited choices of op-amps that can handle as much current as you need:
https://labjack.com/support/datasheets/u3/hardware-description/dac/typic...
It would be nice if your valve had separate connections for signal and power.
Perhaps PWM control would work with this valve? Rather than converting Vmax to smaller DC voltages, it is much easier to turn a switch on/off very fast such that the average power delivered is less.
Unfortunately it looks like most proportional valves don't have separate power, which is going to make them not feasible for my application. I've found another solution that won't require them -- I'll be able to use a standard pressure regulator since hysteresis and cycle times are not a concern. Though PWM is a good idea, because you could probably incorporate a solid state relay somehow.
Thanks for your help!