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Instructables user titaniumw41 writes:

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

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Becky Stern

Becky Stern

Becky Stern (sternlab.org is a DIY guru and director of wearable electronics at Adafruit. She publishes a new project video every week and hosts a live show on YouTube. Formerly Becky was Senior Video Producer for MAKE. Becky lives in Brooklyn, NY and belongs to art groups Free Art & Technology (“release early, often, and with rap music”) and Madagascar Institute (“fear is never boring”).


  • J Love

    This also works really well as a speed controller for the older single speed Dremel tools.

  • Frank Zhao

    If I recall correctly, ceiling fans require a different kind of adjustable switch, and can’t be replaced with light dimmer switches. Wouldn’t that apply to all AC motors?

    I just got a WES51 soldering station today, it’s worth every penny.

  • mistersister

    an alternative approach could be a manufactured inline (corded) lamp dimmer. i’ve been using one bought at the local bigbox HW store for $10 with my iron for several years with great results. it also has the advantage of being significantly more compact and portable. either way, lateral solutions++

  • japroach

    This isn’t exactly variable temperature, more like variable power with the side effect that temperature will tend to tag along.

    You can tell I’ve used an iron like this before.

    btw you can get what *appears* to be an actual temperature controlled iron on focalprice for $12. Although it doesn’t even have a properly grounded plug.. Maybe its a feature for when you need to solder live equipment? lol

  • craig

    Frank, you are correct. Dimmers work well with RESISTIVE loads such as light bulb filaments, heating elements and the like. They do not work well with INDUCTIVE loads such as AC motors. Not to mention that unlike DC motors, you can overheat and destroy an AC motor by running it under voltage. I’ve heard of many people speed controling Dremel tools with dimmers. The AC motors must be so small with so little power consumption, that the under voltage situation is not killing it any faster than those tools normally die. After a few hours one motor brush is usually gone anyways. (ever notice the replacement brushes with the bits?)

  • jammit

    I did something like this myself, except I bought one of those light dimmers that goes into a light socket instead of building one because it was actually cheaper. I also added a diode across the triac because I didn’t want it to go below half power. It allows me to vary the power from 15 watts to 30 watts. I personally feel 15 watts is the minimum useful power.

    You can easily run a 120AC iron from 220AC by adding a series diode, and I’ve run a 220AC iron from 120AC using a simple diode/capacitor voltage doubler.

  • charlie

    i use something similar to this:
    http://www.amazon.com/Lutron-TT-300NLH-WH-Credenza-Dimmer-White/dp/B0000DI241
    more convenient, and likely cheaper than that solution. it works great. i can do a lot of small surface mount stuff with it. you get a feel for the right temp for the job. you don’t need some expensive contraption keeping the tip within a degree of a precise temp. i don’t atleast.

  • The Oracle

    I also have a WES51 and it really is worth every penny. Anyone using a cheap iron is just crippling themself. And, frankly, the temperature is the least of their problems which makes this item just silly.

  • Mateo

    Ah, neat. I made one of these a few years ago. I didn’t know anyone else had ever made one. On mine, though, I added a little red 120-volt light so I would know when it was on. I also added labels round the knob so I can have rough idea of what voltage I have it set to. 90 to 100 volts always seems to work best with my little iron.

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