Variable Power Control for Soldering Pencil Iron (cheap & Easy)




Introduction: Variable Power Control for Soldering Pencil Iron (cheap & Easy)

Portable and nice little bastard....

Step 1: Electronic Diagram

The circuit diagram its based on the Weller WLC100 electronic soldering station, and was reproduced by Tony Van Roon, so you'll sure that this has been test it so many times before...

Step 2: Parts and Tools

You will need:

2 - Diodes 1N4004 (can be from 4004 to 4007, and thus every replacement that exist)

1 - 250k Potentiometer, with its knob

1 - Diac, bilateral trigger type

1 - Triac 400v/25A ( i used the BTA08 at 600v)

1 - Capacitor 823k 250v (83nf, i used a 100nf)

1 - Resistor 15k, 1/8 watt or more

1 - little box to put everything inside.

1 - Switch, should be at least 3A/125v

1 - AC male panel mount power outlet, it doesnt need the ground pin, unless you have a weird iron pencil that need it.

1 - Pre drilled pcb, because its a very simple circuit, but if you know how or want to build your pcb, i will not stop you, its your life, carpe diem.

1 - (in the end i didn used) terminal block so you can tie the power cable to the circuit.

1 - Power Cable (again, it doesnt need to have the ground part)

Cable (at least 18awg)

An the most important things:
Imagination (a lot) and wil.


I used a drill, a dremel and my wlc100 soldering station, a table, light, snacks, food, a bathroom, my house and a ruler, never forget to have a ruler...

Step 3: Measuring and Cutting

You really know what i meant right?

Just focus that should be simple and everything should fits. Theres where the imagination comes true.

My potentiometer was to large so i cut it, just hopes that the vibration and heat doesnt reduce the life of the poor little guy...

You can see that the rectangles holes were cut in X, so it doesnt leave marks and its easier to remove.

Step 4: Soldering

Not so difficult right? well, it depends on your pulse, experience and confidence, but there just seven components, so i know you will achieve it.

If you want you cant test it before in a protoboard (the center and the left pins in the potentiometer in the second photo are those you're looking for...)

Step 5: Fitting Everything In

Go get some whater and eat something, you're almost done...

Slow... almost.. a little to the left... Thats it! you got youself a nice little timey wimey heater thing, a pat for youself in the back.

Now you shold test it, in the original WLC100 says that its only for solderig irons smaller than 300w, so dont be afraid...

Step 6: My Measures

So this is what old friend WLC measures vs the little new town guy...

The crazy thing its that our circuit got a more proportional change in the voltage, so im not sure what to think, maybe there's life in other planets...

But it works, now you got +1 in DIYlogy...

Step 7: If You Like My Work...

If by some crazy reason you think that i should be working for the nasa... who says i dont? well i dont, but anyone can dream...

By the way, if you like what i did and want to support me so i can keep doing it, dont hesitate in donate, i'll really appreciate it...


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    8 Discussions


    3 years ago

    hey andy... I have a question..
    do you maybe know what triac should I use for a 40W soldering iron similar to yours or what could change that triac?
    ...and if you know where could I find that triac on some old PCBs at home... thanks forward :)


    5 years ago on Introduction

    very cool !!! i have ben needing to build one . i do alot of soldering and this would be great , small and looks good. thanks for a job well done !!


    5 years ago on Introduction

    Seems like a +1 in my To Do project list... Good job.


    Reply 5 years ago

    Thanks, i hope yours be better than mine :)


    5 years ago

    like i said, if you can and want to make your own pcb, then do it the way you think is safe, and yes, i forgot to mention that the pcb trace between live wires and the pin 1 and 2 should be tinned.

    I test what you said about the fm interferes in the original wlc100 and the one that i did and can't found anything like you said.

    Also i take photos of the circuit inside the wlc100 so you can see that it is the same, and this have been used at least 10 years or since weller implemented and nobody has complain as far as i know...


    5 years ago on Introduction

    Sorry, I won't be constructive but I can't, this is the worst dimming method ever used, moreover it's dangerous. It should be forbidden, there's no insulation between the potentiometer and live wire, so be extremely carefull. The current curve isn't linear (it's weird in fact, cos it changes with temp).

    The system emits lot of interferences in both low and high spectrum : try to listen an FM radio close to it ! BUZZZCCCRRIICHT.


    5 years ago

    Hey, there was a comment before i edited my instructable and now its gone, sorry nice guy :(