[thermal process] Controlling a heater

Discussion in 'The Projects Forum' started by a_s_impressed, Jul 1, 2008.

  1. a_s_impressed

    Thread Starter New Member

    Jul 1, 2008
    al salam aleikom,

    Problem Description

    I have built a plant consisting of:
    1- A heating room.
    2- A heater. (220V AC)
    3- A sensor. (Thermistor)
    The reading of the sensor is converted into a (0-5V) signal using a traditional signal conditioning circuit.
    Then this signal is read by a PIC16F877 using the A/D module then a control decision is made.

    The problem
    How can I represent the control decision and send it back to the heater?
    I thought of a PWM signal controlling the heater current. However, I don't know how to interface the uController signal into the heater 220V AC circuit.
    One of my friends suggested a TRIAC but I'm not sure if this may help.

    Any suggestions?
  2. bertus


    Apr 5, 2008

    Perhaps you can use a part of the dimmer circuit descibed on this page.


    You could connect R4 to the output of the pic.

    Best is to sync the pic with a zero crossing detector and generate a pulse depending on the power needed.
    When you reduce the powersupply of the rampgenerator, on the collector of Q2 is the zero crossing signal.