After I power it up and do some testing, I found out that the 25W is a bit over heat compare to my old soldering gun. I am a bit regret about choosing 25W, but I don’t think I can return it back because I already power it up and the colour changes of the heated tip is very obvious. So, I decide to add a dimmer to the soldering iron to make it adjustable.
Step 1: Using a Dimmer to Adjust the Power
Also, you will need a box for the dimmer as a protection to the wiring. You can this kind of box (I am not sure what it is called) in a normal electrical store.