Variable Voltage Controller

Discussion in 'The Projects Forum' started by alexilla, Jan 24, 2011.

  1. alexilla

    alexilla Thread Starter New Member

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    I need some suggestions on creating a power supply that is capable of varying voltage from near zero to 120vac at about 3A and is capable of accepting a milliamp signal from a controller IC. I need a very quick response time for partial load to full load voltage. This is for varying the voltage on an electrical resistance heater coil that has to maintain a set airflow temperature through a tube. As the airflow varies from none to high flow, the coil voltage has to continuously adjust to maintain the temperature set point and to avoid damaging the coil when the airflow is minimal. ie... low airflow, low coil voltage; high airflow, high coil voltage. Any help would be greatly appreciated. Thank you.
    Alex
  2. beenthere

    beenthere AAC Fanatic!

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    The resistance heater will operate on DC as well as AC, and with DC you can use a form of PWM to control the heat. Otherwise, you can use a TRIAC to control current.

    That milliamp level signal will almost certainly need amplification. Can you post the schematic?
  3. wayneh

    wayneh AAC Fanatic!

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    That's a unit of measure, not an amount. Do you mean in the hundreds of mA (probably usable without amplification), or single digits (needs amplification)?

    I agree that PWM control of a MOSFET "switch" would be a good option here to control a DC heater, with the PWM being controlled by the controller voltage.

    The old-school approach is a variac under thermostatic control.
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