PC based temperature control


Thread Starter


in my pc based temperature control project i had a problem in final control element. the project is simple; i am going to measure the temperature by thermocouple and it is signal conditioned and send it to pc through Modbus plus. i prepared a program ( PID algorithm) to control the temperature by final control unit ( Thyristor control unit). here i have a problem, how the gate terminal in SCR can be controlled thruogh pc. the voltage rating is 0 - 10v.
if u have any idea please send me reply. or tell me the sites

with regards
Buy a light dimmer, replace the control potentiometer with an equivalent opto-coupled circuit. 40 years ago - I did it with a 2W lamp and an LDR (light dependent resistor).


Hassan Shahzad


Well the final control element in your project is easy to interface with the PC. For example, if you are using parallel port of the pc, you can dedicate a single pin on which you are gona send the pulses for the gate of thyristor.

Coming to the power requirements, you can add two or more stages of transistors to perform isolation and level shifting.

If you need any further help, please feel free to contact at: [email protected]

Take Care,

Hassan Shahzad
(Final year student)
Institute of Electronics & Communication
THe University of Lahore,

you can convert output of your PC to analog and there are some ICs to control triggering angle of SCRs TCA785 I think you can use this.

Johan Bengtsson

It sounds like you need an output card or ouput modbus device (or other) capable of handling 0-10V Since you are already using modbus that would be the easiest.

That is assumed that the thyristor control unit takes an analog 0-10V signal and handles everything else by itself.

There are a lot of other different ways this can be done, however...

/Johan Bengtsson

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