With Instructables you can share what you make with the world, and tap into an ever-growing community of creative experts.
Tell us about yourself!
$10ish DIY Variable Temp Soldering Iron Controller
Here is a little project I did. I scanned the internet for various wattage soldering irons, the less expensive types and looked at their wattage/power rating and temperature. Then I plotted temperature vs. wattage/power. And found temp vs. power to be Temp = 10*power + 300 (in degrees farenheit), or Temp = 10*V^2/R + 300 where R is the resistance of the soldering iron as measured with an ohmmeter. You can also infer the resistance for a soldering iron by the following formula power = v^2/R where v = 110 v and power is the power rating listed on the iron (this is approximate). Anyhow after all that I made out the following chart which can be overlayed onto a dimmer cover plate. I have not tested this but you get the point, these are estimates. Additionally, these irons aren't temperature controlled, I know you have to take into account thermal mass, heating and cooling rates, the mass of the thing you are soldering etc. This is more or a less an estimate of the initial temperature at the tip after the soldering iron has been fully heated and before any solder is melted. There is plenty of room for criticism about the above idea and template, which is not very accurate and certainly not temperature controlled. But I think if you use this to set a maximum temperature, it could be helpful, and is probably more useful to estimate a maximum temperature and then solder an item that has a much lower thermal mass than the iron. Which is a very common situation. Bottom line is, I'll use it to cut my 60 watt or 30 watt iron down to 15 watts, which is safe to solder most common electronic components. See faceplate below:
Ok I made it, and I did a little experimenting. Bottom line is power is V^2/R where power is power dissipated by iron, voltage is the voltage applied, and R is the resistance of the soldering iron. So I measured the resistance of 3 "30 watt" soldering irons hot and cold and found this:Soldering iron 1, 490 ohms cold, 550 hot, iron 2 500 ohms cold 510 ohms hot, iron 3, 650 ohms cold, 550 hot. Anyhow when averaged, that's 550 cold and 540 hot, and I'll just say 545 ohm average altogether. So bottom line is a "30 watt" soldering iron has about 545 ohms resistance, and doesn't change a lot with heating.That leads to the following chart:P=V^2/R ("30 watt" soldering iron)22 watts for 110 volts15 watts for 90 volts10 watts for 75 volts5 watts for 50 volts1 watt for 25 voltsSo although I didn't measure the temperature, this chart should allow yout to label your dial for a 30 watt soldering iron and I attached a picture. Just measure the voltage as you turn the dial an mark those voltages as shown.A 60 watt iron would make more sense actually. In order to make a chart for a 60 watt iron, all that you need to do is measure the resistance of the 60 watt iron cold and hot, make sure they are similar and use those numbers to estimate the resistance.I don't own a 60 watt iron, so if someone does, would you please measure the resistance with and ohm meter cold, then hot. Then I could label this a little better for a 60 watt iron.Great idea, thanks! Here are the pics:
Ok I made it, and I did a little experimenting. Bottom line is power = V^2/R where power is power dissipated by iron, voltage is the voltage applied, and R is the resistance of the soldering iron. So I measure the resistance of 3 "30 watt" soldering irons hot and cold and found this:Soldering iron 1, 490ohms cold, 550 hot, iron 2 500ohms cold 510ohms hot, iron 3, 650ohms cold, 550 hot. Anyhow when averaged, that's 550 cold, and 540 hot, and I'll say 545 average altogether. So bottom line a "30 watt" soldering iron has about 545 ohms resitance, and doesn't change a lot with heating.That leads to the following chart: P=V^2/R ("30 watt" soldering iron)22 watts for 110 volts15 watts for 90 volts10 watts for 75 volts5 watts for 50 volts1 watt for 25 volts.So although I didn't measure the temperature, this chart should allow you to label your dial for a 30 watt soldering iron.A 60 watt iron would make more sense actually. In order to make a chart for a 60 watt soldering iron, all that you need to do is measure the resistance of the 60 watt iron cold and hot, make sure they are similar and use those numbers as an estimate.I don't own a 60 watt iron, so If someone does, would you please measure the resistance with an ohm meter cold, then hot. Just plug it in, let it heat up, pull it out of the socket and measure the resistance across the plug.Great idea, thanks! Here are some pics:
My thoughts exactly
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.
Great instructable, works very well.
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?
Almost made this... rumaging for a wall dimmer switch I thought I had, I found an old one of these:http://www.amazon.com/Lutron-TT-300NLH-WH-Credenza-Dimmer-White/dp/B0000DI241Done! :-P
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.
wood version; don't worry, its has a plastic boxing inside and insolation
Join 2 million + to receive instant DIY inspiration in your inbox.
Download our apps!
© 2016 Autodesk, Inc.