Low Cost Soldering Iron Inverter

This circuit is a very simple but low-cost inverter for making use of a small power soldering iron (25W, 35W, and so on) in the absence of mains supply. It requires eight transistors along with a number of resistors and capacitors.

Transistors T1 and T2 (each BC547) build an astable multivibrator that generates 50Hz frequency of wave signal. The complementary outputs from the collectors of transistors T1 and T2 are fed to pnp Darlington driver stages formed by transistor pairs T3-T5 and T4-T6 (using BC558 and BD140). The outputs from the drivers are fed to transistors T7 and T8 (each 2N3055) linked for push-pull operation. Use appropriate heat-sinks for transistors T5 through T8.

Low Cost Soldering Iron Inverter Circuit Diagram

A 230V AC primary to 12V-0-12V, 4.5A secondary transformer (X1) is utilized. The centre-tapped terminal of the secondary of the transformer is joined towards the battery (12V, 7Ah), whilst the other two terminals of the secondary are joined for the collectors of power transistors T7 and T8, respectively.

At the time you power up the circuit by activate the switch S1, transformer X1 delivers 230V AC at its primary terminal. This voltage could be utilized to heat your soldering iron.

You can build the circuit on a general purpose PCB and house inside a appropriate cabinet. Connect the battery and transformer with proper current-carrying wires. Around the front panel of the box, fit power switch S1 and a 3-pin socket for connecting the soldering iron.

Note:
That the ratings of the battery, transistors T7 and T8, and transformer may possibly change as these all rely on the load (soldering iron).