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There are a lot of different products that use heating elements. Unfortunately, many of them are not adjustable. For instance, most soldering irons are either on or off. It would be much more useful if you were able to change the temperature of the iron. This would allow you to use the soldering iron for lower temperature applications.

So I designed a simple control circuit that will let you adjust the output of a heating element.

Step 1: Watch the Video

Here is a video walkthough of the project.

<p>Can this be replicated for an appliance that has a ground plug? </p>
<p>Yes. Just connect the ground wire of the input to the ground wire of the output directly.</p>
Is there any reason R1 couldn't be a potentiometer?
How would I make the &quot;on time&quot; adjustable?
<p>Use the formulas in step 3.</p>
<p>This is not a controller. If a lot of heat is used, the temperature will drop. A controller measures and compares with the value of the setpoint. Based on the difference between measured value and setpoint it will control the heat.</p>
<p>Most controllers for heating elements don't have feedback. They just set a certain output. Then the user adjusts the setting to compensate for the environment and working conditions.</p>
<p>can anyone tell me where to get the 5v relay, and how to wire the 4 pins to the circuit.</p><p>Please.</p>
You can purchase them from Radio Shack or any online electronics parts distributor. I frequently use Mouser.com. <br /><br />Just connect it according to the circuit diagram. If you need help reading the circuit diagram, check out this Instructable:<br />https://www.instructables.com/id/HOW-TO-READ-CIRCUIT-DIAGRAMS/<br />
Have there been any issues with the contacts sticking? From my experience each time a contact opens there is a spark generated. This causes not only carbon build-up but also heats those contacts which will end up welding them shut...Unless there is as spark arrestor.
That can happen. It have only happened to me when it is turned on and off rapidly. If you keep a low duty cycle it should be a problem. You can also replace the relay with a solid state relay to avoid that problem.
<p>This is a very documented &amp; clean ible! Although I'm still trying to figure out if there is any functional difference between this &amp; an off the shelf sliding lamp dimmer? </p><p> Also, just a thought, with some minor modifications and substitutiion of a thermistor for the potentiometer you could give this controller a feedback feature.</p>
This kind of circuit can be a lot more precise than an off the shelf dimmer. It also has a wider operating range. Dimmer only work in the range where a light bulb would glow.
<p>Annnnnd I just thought about it and realized that the sliding lamp dimmer reduces the voltage going to the output while your device uses PWM. </p>
<p>Just an idea.. But you could open up the 5v transformer and wire it to the &quot;lamp cord&quot; (before the relay of course) and tuck everything inside a bigger project enclosure, that way you would only have to plug one cord in.</p>
Yes. You could do that I was just trying to keep things simpler.
<p>I couldn't find a note regarding safety thus I want to remind everybody who plans to build this to keep a decent isolation distance between mains and the circuit. Keep at least 5mm distace, the more the better, and remeber to remove any surrounding metal (yes, this incudes the pads).</p>

About This Instructable

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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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