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3. Proportional Control

A proportional controller offers much better stability than an On/Off controller does. In proportional controllers, there is always a residual error, even after the controller has settled to the final state. This error is proportional to the difference between the set-point temperature and the ambient temperature. The following diagram is a linear bipolar proportional control circuit.

NOTES:

  •  OP - AMP
  •  SET CURRENT LIMIT <2.0 AMPS.
  •  INCREASE GAIN UNTIL OUTPUT STARTS OSCILLATING, THEN CUT IN HALF.
  • ¯ CHOOSE C1 TO OBTAIN STABILITY AT HIGH SETTINGS IN HEATING MODE.
  • ° TEC IS A 2A @ 2V MAX, WHEN BASE TEMP = +27°C

6. R1 IS CURRENT SENSE RESISTOR, .3 OHMS, 3 WATTS.