Controlling solenoid with PID output

[nonenanone]

I’m reviewing the possibility of using a PID in conjunction with our cooling setup where a solenoid valve is turned on and off.  I found a VI with a PID that was used with variable pump speeds to regulate pressure and I’m trying to make it easy on by plucking out that portion of the program which is attached here.  Unless I’m completely on the wrong track what I would like to know is how I can use the output or “result” to regulate the valve.

[StevenA]

nonenanone

What kind of valve is it?  You mentioned that it was a solenoid valve, but is it a porportional solenoid?  What kind of system is it?

[Sappster]

It's hard to say without knowing how you control your solenoid, but you can use the RESULT you get from this VI and convert it to a voltage or PWM to control the solenoid. If you can explain how the solenoid is controlled, then I can provide a better explination.

[nonenanone]

It is a cryogenic valve and it is either on or off.

[Sappster]

One possible solutin is to take the result reading from your VI and use it as the duty cycle for a pwm to control the solenoid. You might have to scale the result to get the appropriate duty cycle. Did you create the PID.vi? If so what does the result represent for your situation? Is it a time length to keep the solenoid open or is it a percentage the solenoid needs to be open, etc?

[nonenanone]

Former employee created the PID to vary pump speed based on a pressure set point, so I’m not sure how applicable it is with simply turning a valve on and off.  If the valve were proportional it might be easier to adapt.  I am interested in a length of time function that can be controlled with the PID so the temperature can be adjusted to the set point more and or less aggressively.  I do have a program that allows me to vary the cycling of the valve, but if it included a PID it would be more of a hands-free operation.  As it stands now, I have to make changes to the cycle rate every couple minutes while the temperature transitions into the set point.  As the temperatures moves into equilibrium, the valve is open for a shorter duration of time and or closed for a longer period of time.

[nonenanone]

I searched PWM and noticed the FieldPoints rate away, as well as them being DC.  I have a FieldPoint and we are using a 4 to 20 mA.

[Sappster]

What Fieldpoint hardware are you using? What is required to turn the solenoid on and off? I'm not sure I follow the last post but does the PWM suggestion not work?

[nonenanone]

I'm using a FP-AI-100 and the valve is 120 volts, 60Hz, 14.25 watts.

[nonenanone]

Ops, sorry... FP-RLY-420