The Soldering iron is a vital tool to the electrical engineer and hobbyist. After many years of experience with soldering, both Jake and I were curious what new innovations we could bring to the conventional, plug-in, soldering iron. Soldering by itself, requires multiple tools, such as a fume extractor, lighting, and other hand tools. Our goal was to see how much we could streamline this design on the Soldering Iron itself.

What it does

The Soldering iron is a conventional, plug-in iron without any temperature control. Anyone who has some experience with soldering knows that temperature control is vital to the iron's ease of use and longevity. We are using Pulse Width Modulation signals from an Arduino Uno to a Solid State Relay, which switches the Soldering Iron on and off at a rapid rate. This system of PWM can help maintain a constant, operational temperature without overheating, which is a common problem of these types of soldering irons. We also have an optical sensor which detects when the iron is placed within its base. When the soldering iron is in the base the optical sensor is triggered, and the PWM signal will eventually slow down. This will cool the iron to a set, idle temperature. This will increase the life of the iron, and draw less power when not in use. Once the iron is removed form the base, the PWM signal will resume as normal, and the iron will rise to its operational temperature. Additionally, we have used an aluminum tube, vinyl tubing, and a fume extractor, to build a small fume extraction system attached straight to the iron. Lastly, there was a small LED attached to the iron to increase visibility while working with the iron.

How we built it

We started off with a simple Soldering iron, and started designing new attachments for it. We 3D printed the clips for the fume extractor tube and LED, and routed the extraction tube, LED wire, and Iron wire to a central control box. Additionally, we glued the optical sensor onto the base for the soldering iron, and routed another set of wires to the control box. Within the Control box, we soldered a prototype arduino shield for this project, which held the inputs for the Solid State relay and optical sensor. The arduino is powered but a 9v Power adapter, while the iron itself is powered by just AC voltage.

Challenges we ran into

So initially the fume extractor that we had built, did not have enough suction for the fume extractor assembly of our project. We got to remedy this problem with a high pressure 40mm fan that was generously donated to our project. Additionally, there were no arduino temperature sensors, such as TMP36 or DS18B20 that could really handle the high temperatures of the soldering iron, so we used a thermocouple to measure temperature instead. While developing our code for the regulation of our soldering iron, we also ran into a number of problems. One rather frustrating and time consuming example of these problems would be the overflow of memory when dealing with time counts. For the standby-temperature-drop to kick in after a duration of idleness, we used the millis() command and an unsigned int assigned to a reference time to compare time differences as a means of calculating the desired duration of time. We ran into our problem when, after only around 65 seconds, the reference time would overflow and start recounting from 0 milliseconds, while the millis() command would not overflow for about 50 days. Though this wasn't a terribly challenging problem to correctly address, the fact that it didn't arise until after the code functioned correctly for some time made it rather elusive while troubleshooting.

Accomplishments that we're proud of

We managed to successfully 3D print many of our parts. There were many obstacles especially with the fume extraction system that we struggled with, but managed to push through regardless. Our project is also applicable to any soldering iron of the same size, and more with slight modifications!

What we learned

We learned a variety of skills from checking values at points in code to troubleshoot, to an easy way to expand a small hole without a drill by sticking the end of a pair of needle nose pliers in it and twisting to grind away at the inner diameter. We learned how to use a solid state relay and what it really is. We also learned the important difference between flow and pressure, as well as the importance of resistors when dealing with IR LEDs! Overall, we learned these and plenty other techniques for brainstorming, improving and, of course, troubleshooting our project to make the presentable product we have today.

What's next for Fire in the Hole

Perhaps streamlining the design and making the circuit more space efficient. Making the temperature control more accurate with the incorporation of a thermocouple directly attached to the iron. We will definitely look to add ideal-temperature-range indicators for popular solder gauges and types. We'll be sure to ignite the fire in the hole!

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