Soldering Iron Regulator Circuit Diagram

Soldering Iron Regulator Circuit. By connecting this simple circuit to a soldering iron with a built-in thermoelement, you can easily regulate its temperature. The opamp functions as a comparator and compares the voltage value at the thermoelement with the voltage at the potentiometer P1. As long as the voltage at the minus input is lower than the voltage at the plus input, the IC is positive and T1 conducts. The relay then closes and switches on the power of the soldering iron.
soldering-iron-regulator-circuit-diagram
Soldering Iron Regulator Circuit Diagram

Soldering Iron Regulator Circuit

By connecting this simple circuit to a soldering iron with a built-in thermoelement, you can easily regulate its temperature. 

The opamp functions as a comparator and compares the voltage value at the thermoelement with the voltage at the potentiometer P1. 

As long as the voltage at the minus input is lower than the voltage at the plus input, the IC is positive and T1 conducts. The relay then closes and switches on the power of the soldering iron.

The reference voltage is varied through P1 and at the same time it varies the temperature of the soldering iron. 

Calibration: Common thermoelements produce an output of 5 mV per 100C. Turn P1 to the right until the relay closes and the soldering iron begins to heat up. 

Using a voltmeter, monitor the voltage at the minus input of the opamp and turn P2 until the relay opens when the measured voltage is 20 mV which is equivalent to 400C.