Hello everyone,
I want to regualte the pressure on a device I have, and I have been given the Kelly pneumatics Low Flow Electronic Pressure Regulator. However, I have questions about it. It has four wires as you see in the picture.
I know how to connect the power supply and ground, but I got confused between the control and feedback signals.
What code should I use? and how to connect them to the Arduino?
Thank you
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You need to look at the manufactures web site .
Depending on the model you have the input signal is the desired output pressure ( set point ) and is 4-20mA, 0-5v etc depending on the model you have.
The feedback I’m not so sure about but imagine it’s the outlet pressure signal, which could be used for integral control if you wanted it ( it’s a proportional regulator ) .
Don’t forget the UNO , Nano does not have a true analog output
Don’t forget that neither UNO nor Nano (nor Leonardo or most other Arduinox) has a true analog output. 
What do you mean by true analog output? How can it be fixe
The analog output is a pulse width modulated output - so the “average value “ of the pulse -space varies from 0 to Vcc .
You need a smooth DC value , you might be able to make a CR network ( google) to filter it .
I was able to run the pressure regulator and control how much pressure it regulats based on how much voltage I give the control signal wire. My question is
I will be connecting the regulator to a 12v power supply and then connect it to the (vin) in Arduino. Where should I pin the control signal wire in Arduino?
After that, I should use resistors to change the amount of voltage right?
Your control signal wire needs to end up on one of the pwm pins ( use 5 or 6)
So an analog output of 255 will give 5v and 0 will give 0v , 125 a pulse train of about 50%/50% off ( average ~2.5 v .
Google pwm output Arduino .
That signal is thus a series of pulses . To get a smooth DC , that the pressure controller wants , you need to try a low pass filter . Try something like a 4k7 resistor -Arduino to input of transducer . Then a capacitor from that input to ground - something like 470 micro farad - that might not. Be enough .
Suggest you google “pwm filterArduino”
There might be something on increasing the pwm frequency (?) worth googling that too
There are some Arduino versions with true analog outputs , that’s an alternative
Google is your friend
But they only work in a limited range of output voltages. You can not get a rail to rail output from them. And they are all 3v3 systems, not 0 to 5V.
Ho hum 
The red wire is 12V( the device power supply) and the purple one is the ground. The white one is the control signal (0-5v) I am trying to figure out how to connect it all of that with the Arduino & breadboard?
Ground to Ov on Arduino .
As said before you need a filter to get a steady 0/5v from the Arduinos pwm output ( white wire ) .
If you have no other connections to the Arduino you can connect the 12v to Vin on the Arduino and power it that way .
Draw yourself a basic wiring diagram and post up here
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