I need help in designing a better circuit to control the SSR. The circuit that I have now to control the SSR will not work. I am open to any suggestion to improve my circuitry.
If increasing the cost marginally will not break the bank, I would suggest designing this around an 8-pin AVR micro-controller with at least one analog input and driving an off-the-shelf SSR with 3-32VDC input, switching 220VAC. Off-the-shelf SSRs are available in various output amperage ratings.
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A micro-controller based design will in addition be deterministic, will allow the use of PID routines to control your heater and be easily re-programmable for various models of RTD.
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Sorry about the last circuit diagram - it is erroneous on account of my reading the wrong datasheet. Here is a corrected cct diag...
That's definitely a poor and probably useless temperature control circuit. The tiny processor solution (could be also a small PIC of course) would achieve lowest overall part count, but unfortunately require programming.