Solenoid pneumatic 2/2 control valves to a proportional flow pneumatic valve. I was hoping to use a range of 0-5V to determine the flow rate of the valve. I understand that there might be some electronics involved. So far what i have learned is that i use a Pulse width modulated driver and feed in the voltage into it to determine the duty cycle.
First, are you looking open or closed loop control? if open loop, then you need a low friction valve (lapped spool?) otherwise response to a signal ramping up will be significantly different than a signal ramping down (bad hysteresis). You need a solenoid that produces significantly more force than is required to shift the valve so that it can actually be controlled, and the last problem is the shape of the core, since the magnetic force increases significantly as the gap closes; the valve once it starts to move, tends to move all the way. The proportional valves are not that expensive when you have to deal with all these things.

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