Vision 120-22 from Unitronics PLC....

I have two relay outputs, these are connected to a DC motor....The input to the PLC is a temperature reading. I already have a circuit made that connects the relays and the motor. But I don't know how to program the PLC or how to connect the relays to the PLC in order for it to make the motor turn one way if the temperature is too high or the other way if its too low. mmmmm...that's the essence of it...any ideas? I really reallyyyy need some help. Thanx.

I have been in more "argumentive discussions" because of student questions then I can count.

If this is a homework assignment please state so and give all the details.

For the life of me I can not visualize where reversing a motor will have a bearing on temperature.
BUT

You can use compare instructions, with conditions, to make the motor work as needed.

  Greater or equal  motor CW 

|----| |--------------( )-|

| less than         motor CCW

|----| |--------------( )-|

Yup....its a homeowrk..kinda...but...

I'm doing it for a company. This is a control system for a rechiller tank. The water that goes in at 38 deg F. must come out at 32.5 deg F. The thing is that the water is chilled with ammonia....and dependeding on the pressure, ammonia cools more or cools less. So the PLC has as an input an RTD, and as an output the relays and the motor. The motor is connected to a pressure regulator, which moves a valve to make the tank have less or more pressure. All the circuit does is move a valve to increase or decrease pressure. Thank you very much for your answer.

I FEEL A NEED FOR A NISE PID LOOP IN THE AIR.