Soldering irons are available in different wattage and usually run at 230V AC mains. However, these have no temperature control. Low-voltage soldering irons (e.g., 12V) generally form part of a soldering station and are designed to be used with a temperature controller. A proper temperature controlled soldering iron or station is expensive. Here is a simple circuit that provides manual control of the temperature of an ordinary 12V AC soldering iron.
Temperature Controlled Soldering Iron Circuit
![temperature controlled soldering iron circuit](https://www.electronicsforu.com/wp-contents/uploads/2016/05/7E4_simple.jpg)
The circuit consists of power switch S1, TRIAC1, DIAC1, potentiometer VR1, resistors R1 to R3, capacitors C1 and C2, and step-down transformer X1. Adjusting the resistance of VR1 changes the charging rate of C1 to regulate the conduction angle of TRIAC1, and hence the output power (heat) of the low-voltage soldering iron connected to X1. The red LED (LED1) indicates the power status.
Assemble the circuit on a general-purpose PCB and enclose in a suitable plastic box. Since the front end of the circuit is directly connected to 230V AC mains supply, never attempt to operate the circuit without the cabinet. Use a heavy-duty potentiometer with plastic shaft and a knob for temperature control.
The article was first published in January 1997 and recently been updated.
Hello. Why I control 220v section of circuit instead 12v section? And what hapend with the LED in case of reducing tension?
Can we use a 24 volts soldering iron instead of 12 volt by just changing the transformer and with no other changes in the circuit? Because as far as I know 24 volts soldering iron are more easily available in the market.