CONTROLLING BALL VALVE USING 4-20ma Signal

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saintblues

Joined May 15, 2020
15
Hi,

this is going to sound very basic but i need the wizards help. so im wiring up a classic car heater and am thinking of using a 12V electric ball valve to control the water flow of the engines coolant to pass into the heater matrix. I would like to control the proportional adjustment of the valve using a potentiometer; so as i rotate the pot the valve opens gradually and allows more or less water into the heater matrix thus giving me temperature control of the air being blown into the car. the car has a 12/14v battery.

The specs of the valve are below:
Model Number CTF001 Modulating type
Rated Voltage 12V
Working Current <200ma
Output torque MAX 6Nm
Full on off time <30s
Control Mode 4-20ma
working pressure 1mpa
power <5W
medium temperate 0-95 degrees celcius
IP 65 rated

I'm confused as to how this would be wired up and what rated pot i would use. Ive attached a picture of the valves wiring diagram which is in Chinese english lol so is hard to make sense. if someone could take a look and guide me in the right direction.

looking forward to having my mind cleared up

wiring.png
 

kubeek

Joined Sep 20, 2005
5,724
Yellow and blue is your power supply. You should measure the resistance between red and black to find the internal imepdance of the input (should be around 250 ohms), and with that you can calculate a resistor and potentiometer such that you get 4mA with the highest pot resistance and 20mA with the lowest pot resistance of 0ohm.

Say the input impedance of the valve is 250ohms, then you need minimum total resistance to be 12V/0.02A=600 ohms, so you need a 600-250=350ohms resistor in series with your pot.
The resistance to get 4mA will be 12V/0.004A=250+350+R, so R=2400 ohms. So you use a 2K5 potentiometer, with the center pin connected to one of the ends depending on which way you want it to function.
Adjust to your actual input impedance and let me know how it went.
 
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Thread Starter

saintblues

Joined May 15, 2020
15
Yellow and blue is your power supply. You should measure the resistance between red and black to find the internal imepdance of the input, and with that you can calculate a resistor and potentiometer such that you get 4mA with the highest pot of possibly 250ohms resistance and 20mA with the lowest pot resistance of 0ohm.
thanks mate, i dont have the valve on me. ill have to ask the manufacturer to do that for me. i take it i dont need to connect the 4-20ma output as i wont be needing feedback
 

Thread Starter

saintblues

Joined May 15, 2020
15
Yellow and blue is your power supply. You should measure the resistance between red and black to find the internal imepdance of the input (should be around 250 ohms), and with that you can calculate a resistor and potentiometer such that you get 4mA with the highest pot resistance and 20mA with the lowest pot resistance of 0ohm.

Say the input impedance of the valve is 250ohms, then you need minimum total resistance to be 12V/0.02A=600 ohms, so you need a 600-250=350ohms resistor in series with your pot.
The resistance to get 4mA will be 12V/0.004A=250+350+R, so R=2400 ohms. So you use a 2K5 potentiometer, with the center pin connected to one of the ends depending on which way you want it to function.
Adjust to your actual input impedance and let me know how it went.
just another question, whats the difference between the BLK wire the common vs the BLUE wire the negative? can they simply both be connected to ground?
 
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