$10ish DIY Variable Temp Soldering Iron Controller




This instructable will show you how to make your Radioshack "firestarter" soldering iron into a variable temperature version using around $10 in parts. This idea came to me after i started lifting traces on a circuit board because I was using a 30w soldering iron to solder on a chip. Plus, I am cheap and variable temp soldering irons cost a lot more than $10. Caution: this instructable deals with household AC current. If you don't feel comfortable wiring things up or plugging things in, this is not for you. Also, this is my first instructable so I'm sorry if it sucks.

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Step 1: Parts You Will Need

Flat Head Screwdriver
Wire Stripper
Tin Snips or a dremel

Grounded wire pigtail (mine came from a florescent light, you could just cut the end off an old computer cord. Just make sure it has clearly defined wires. (i.e hot, neutral, ground.)
Romex Connector
4" x 4" Handy Box
4" x 4" Handy Box Outlet / Switch Cover + included screws
600w rotary light dimmer + included screws and wire nuts (mine is made by Leviton and was the most inexpensive model at home depot.)
Lamp with incandescent bulb for testing.

Step 2: Assembly

1. Take the lock nut off of the Romex connector and slide it onto the wire with the screw down clamp side towards the plug.
2. Pop out one of the holes in the handy box. I chose the top center one because it seemed like it would give me the most room to put the rest of the components in there.
3. Put the Romex connector through the hole you punched out and thread on the lock nut. Tighten it down as much as possible with your fingers. DO NOT TIGHTEN THE WIRE CLAMP YET!
4. Separate and peel apart the wires. A knife might be helpful here depending on your cord.
5. Use the wire stripper to strip about half an inch of insulation off each wire.
6. Break off the "ears" off the outlet. These are the things that stick up by the outlet screws.
7. Use a pair of tin snips (what I used) or a dremel tool to cut the excess aluminum off the lamp dimmer. Since the handy box cover has indents where the screws are, we need to modify the dimmer a bit. I cut just above the plastic screw holes on the top and bottom of the dimmer and it fit perfectly.
8. Wire up the components. Isolate the black (hot) wire of your pigtail (mine was conveniently marked with black insulation under the white) and attach it to one of the black wires on the dimmer with the included wire nut. Next, take the other black wire and attach it to the brass screw side of the outlet (if you look really close on the back of the outlet you'll see that it says "hot" on the brass side.) Now, isolate the white (neutral) wire of your pigtail and attach it to the silver screw side of the outlet. Finally, wrap the ground wire from the pigtail and the ground wire from the dimmer together and attach them to the ground terminal on the outlet. That's it! If you got confused your dimmer comes with a wiring diagram. Just substitute the light bulb for an outlet and you're good to go.
9. Screw the dimmer and outlet onto the handy box cover with hardware included with the cover.
10. Make sure all wires and components fit easily into the handy box and screw handy box cover to the box.
11. Make sure there there is a little bit of slack on the pigtail inside the box then tighten the screws down snug. Not so snug that you short out the wires, just snug enough to hold the pigtail securely.
12. Finally, you are ready to test! Go find a lamp with an incandescent bulb (you still have one, right?) and make sure the lamp dims when you turn the knob and goes on and off when you push. I recommend getting a marker to put a + and a - at the appropriate places on the dimmer so you don't have to guess when you plug your soldering iron into it.
13. Have a beer, you're done! (unless it didn't work, in which case you should go back and figure out what happened.)

Step 3: Conclusion

You could probably use this for a variable speed controller for a dremel tool as well, although I haven't tested it. Just make sure you don't exceed the 600w rating of your dimmer. Thinking about it now, it would be really nice to have one of those outlet / pilot light outlets so you could see if the controller is on or off. Hope you enjoyed my instructable!

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121 Discussions


3 years ago

I understand that you can control the watts with the dimmer switch but how does the iron get more wattage? If you plug an iron into a normal socket doesn't it get a full dose of the electricity from the socket?

2 replies

Reply 3 years ago

The iron won't use any more wattage than it is rated for. With that being said what you are actually doing in this circuit is adding resistance, which in any circuit when one variable changes there is either a rise or fall of another of the 3 ( Voltage, Resistance, or Amperage). The voltage of this will remain at 110-125 VAC, while the amps will change resulting in a rise or fall of wattage. Hope this helps you understand a bit more about what you are actually doing by using this with whatever you have plugged into it. If not do some research on the relationship between Voltage, Resistance, and Amperage. Happy building.


3 years ago

Great instructable, works very well.


3 years ago

Almost made this... rumaging for a wall dimmer switch I thought I had, I found an old one of these:


Done! :-P


3 years ago

Most of you can barely write and you are going to mess with electricity?
Yes the dimmer will work, for the unskilled just remember that black wires go on the brass screw ( B on B)
Will not matter if you use top or bottom screw or any combination as they are tied together. Do not use two wire lamp cord as your power cord, use three wire and attach the ground to the metalic box and the ground screw on the duplex recepticle, plug a cheap nightlight in one plug to let you know the power is on, don't use a led as they don' like dimmers, always unplug the unit when not in use. You can buy dimmers with a built in led but it shows light when off and goes out when switch is on so it could be confusing and lead to an accident. Ad in burn your house down.

1 reply

Wow--check out your last sentence and then read and consider your first sentence. Perhaps you should stick with low voltage, low amp. DC projects while brushing-up on your remedial English.

Hey--I'm pullin' your chain--no harm intended--couldn't resist the temptation. PAX!!


8 years ago on Step 3

ALSO you could use an amp meter to see how many amps the iron is using then multiply amps by volts and that will give you watts! you can then mark on your dimmer control box where 15 watts is 20 watts 25 watts 30 watts 35 watts and 40 watts are!!! hope this helps

4 replies

Reply 3 years ago on Introduction

Would you mind elaborating on this? I would love to this and have tried to get a reading from mine while plugged into the outlet only to switch the breaker in my house (bad idea). Thanks.


Reply 5 years ago on Introduction

i've read that current draw might be proportional to tip-temperature, and will therefor vary as temp varies. Anyone know if this is correct?


Reply 4 years ago

Bro i think you are correct as I to reas about it and a practical on it


3 years ago on Introduction

Awesome idea, man! Thanks so much for sharing. Going to totally do this tomorrow! :)


4 years ago

20$ mutimeter at Harbor Freight has a Celsius temperature readout, and a temperature probe. just check temperature, use online celcius ferenhight conversion calculator. adjust dimmer..wait for temperature to settle, recheck. when correct temperature is reached mark the dimmer selection spot.


Reply 7 years ago on Introduction

No! Don't do it! It the dimmer is rated for 600 watts max, and some of the aluminum for cooling has to be cut off to fit it in the box. It would be a good idea to stay under the 600 watt rating.

After doing a little research I found the Harbor Freight has a Router Speed Control. Basically used the same was as this dimmer. The Router Speed Controller is $19.99 online.

The controller is 120 v x 15 amps. Wattage = Voltages x I (current). So, the Router Speed Controller is rated as 1800 watts.

I found some companies to have 2000 watt dimmers. Did not see one on Home Depots website. Maybe a lighting store would have one. Also, homedepot has a 20 amp Plug/Receptacle. You could probably use that in Titaniumw41's plans with the 2000 watt dimmer to control the heater temperature.