PTC Heater for PID
- PID control output is an analog output to control the power rate.
PTC has Curie point. When the temperature is over Curie point, its resistance is bigger, and power rate is small.
During PID control, if the PTC enters into Curie point, the control fails.
- PTC selection:
Do not use PTC heater in photo P1, even the Curie point is 270 degree.
Nor in P2.
But in P3.
- Fan power rate:
Should be enough to blow out the heat energy on heat-sinker, to avoid enter into Curie point.
And this could make the inertia of heater small.
- Sensor position:
Sensor should be situated in the return air position.
Not before the air comes out from heater.
Nor at the middle way of the circulated air path.
Ref. drawing: P4
With the above, the PTC can work well with PID.