DIY 35W Soldering Iron Two-Stage Control

If you have a 35W soldering iron with a built-in heater, and you often run into the problem of the tip oxidizing due to high temperatures—forcing you to resort to sandpaper or a file, which wears out the tip way too fast—then what can you do about it? If this sounds familiar and you're curious, keep reading.

You can try mimicking a simple temperature control circuit like the ones used in electric heating pads, and add a two-stage temperature adjustment to your soldering iron.

First, you need to pick a power plug that fits your size requirements. (Some commercial plugs come with a switch, but their slightly bigger size might block neighboring sockets.)

Next, remove the grounding pin from the plug and drill a hole in the plastic casing to install the temperature switch:

After that, you can test how the switch fits in the casing—if it looks good, you're all set:

Here's the two-stage temperature control circuit:

Then you need to solder the temperature control circuit and assemble the plug casing:

After everything is set, you can power it up for testing. If it works properly, great!

When the LED is on, the soldering iron runs at half power; when the LED is off, it's at full power, as shown below:

Done.