Temperature control anybody?


Thread Starter


I am required to design a program that will control the temperature of an oven. The operator will be allowed to enter a set point temperature in the range of 0 - 99'c via a thumbwheel switch. Upper and lower set point values are to be calculated which will be used to switch the oven on and off when the actual temperatures are reached. The actual temperature of the oven is to be displayed at all times during operation.

Oven spec:

Oven on/off control Y10
Actual oven temp Ch2 FX-4AD, position 1
Temp resolution 10'c/volt
Thumbwheel switch X20-X27 BCD format
Seven segment dislay Y20-Y27 BCD format
Up and Low set points +/- 1'c

If anyone can help me with any information I would be entirely grateful

Jake Thompson

Hello Mike,
I would like to suggest using an e100 operator interface ratherthan using thumbwheels and a seven segment display. This will save you alot 16 IO. If you choose to a thumbwheel and display there are instructions to take inputs and convert that to HEX and visa versa. As far as the control part of things you will need to take in the analog value into a data register and you can use the ZCP instruction, this compares a high and low range against a current value. This will give you a the high and low setpoints for the oven.

Good Luck, this sounds like a fun project!
Why use a PLC? Are you trying to coordinate other actions with the reaching of a particular temperature? You can buy dirt cheap (<$150 US) single setpoint temperature controllers or multi-setpoint/time controllers (<$200 US), especially since your control mode is ON/OFF, not PID, from Omega.com, Yokogagwa, West, Honeywell, Barber Coleman/Eurotherm, Watlow, etc. These controllers have an interface and display built in. No programming, connect power(3wires), T/C(2 wires) and output (2wires) for a total of 7 connections. The controller alone will cost less than the PLC interface and your programming time is probably more valuable than the controller.

If your trying to do more than that a PLC might be advantageous, you weren't very specific. I've done dozens of vacuum furnaces, some simple, some very complex. They are one of my favorite kinds of projects. Send me an email if you want more information.

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