When it comes to creating electronic circuits on a piece of perfboard, you will always need a decent soldering iron. Now i've been using my Ersa i-con Pico soldering station for two years now and it still works perfectly fine. But there's another popular soldering iron/station manufacturer called JBC which supposedly sells the best of the best. Only problem is, that their products are ridiculously expensive! So much so that their cheapest soldering station goes for roughly 500 dollars. But on the other hand, the soldering iron itself only costs around 70 dollars. Plus a 30 dollar soldering tip. So, needless to say, I got myself those two components. And in this video, I will show you how I created a suitable soldering station that can heat up the iron up to 400 degrees celsius and keep the temperature decently stable. Let's get started! (Intro Music Plays) First off, let's have a closer look at the soldering tip. As you can see, it has 3 important looking contact points which was also confirmed after I unsoldered three wires from the plaque of the iron. The metal body of the tip and the contact point right next to it, had a resistance of around 2.9Ω. While the other terminal featured a resistance of almost nothing. This led me to believe that the first and bigger resistance was a heater. And the second one was some kind of temperature sensor. So I fired up the lab bench power supply and connected it to the alleged heater terminals to find out that it not only reaches the current limit of my supply but also heats up the tip simultaneously. Which means that, for a change, I was correct! And measuring the voltage across the metal body and the third contact point while heating up the tip also revealed that the voltage dropped slowly but steadily increased. Which means that it acts like a thermocouple. Those basically consist of two different metals which creates a voltage drop proportional to the temperature. And thus it can obviously be used as a thermometer. And even though it is unclear which exact type of thermocouple was used inside the tip, it seems like a common type K thermometer circuit delivers acceptable values. The only thing we have to keep in mind for later is that by powering the heater, we cannot simultaneously measure the correct temperature. Since the sensor and heater share a common terminal and thus the voltage drop of the heater current distorts the thermocouple voltage. But nevertheless, after reinserting the tip and measuring the resistance between the three soldering iron wires, I asserted that red is the temperature wire, blue is the heater wire, and green is the common ground wire. After powering the heater through the corresponding wires, the tip still heated up properly, but with a current flow of only 3 amps, it took around 37 seconds to reach a temperature of 300°C... ...which could be enhanced. Thankfully, though, I had a couple of toroidal transformers laying around that I salvaged from my previous lab bench power supplies. This one offers 6.7A at 15.5V RMS. Which, after hooking the transformer up to mains voltage, and connecting the red wires to the heater wires, equaled a 300°C heat-up time of only 12 seconds, at a current draw of 5.4A. Sounds great, but in order to control the AC sine voltage applied through the soldering iron we need a triac. In this case, a BTB26, which can handle this kind of current without a problem. But, adding an additional heatsink is always a good idea. After connecting it in series to the AC voltage source and the soldering iron, it obviously doesn't want to turn on by itself. For that, I utilized an Arduino Nano to which I firstly added an OLED LCD to display the set and measured temperature, A MAX6675 thermocouple-to-digital converter to measure the temperature of the tip, and a potentiometer to set the target temperature. After connecting the MAX6675 thermocouple terminals to the sensor wires of the iron, and uploading a simple test code, which only checks the functionality of the three attached components so far, we can see that the system successfully measured the temperature and sets the target temperature according to the position of the potentiometer. Now, in order to control the sine voltage applied to the iron, we basically have got two options: The first one is called Phase Angle Control — in which we activate the triac after the voltage crosses the zero-point and thus, only lets a complete part of the half-wave pass. This way, we can control how much power the iron receives. But, on the other hand, this method also creates undesirable deformed power. The second, more appropriate method either lets the complete half-wave pass, or blocks them entirely. This way, we can also regulate the power, and, don't have to worry about negative side-effects. But, with either option, we have to detect when the sine voltage crosses its zero-point, so that we can activate or deactivate the triac accordingly. For that, I firstly added a *ECHOING VOICE* FULL-BRIDGE RECTIFIER to the transformer output, which converts the negative half-waves to positive ones. This rectified sine wave then connects to the LED side of an optocoupler, while the other side connects to pin 2 of the Arduino, which is an input with a pull-up resistor, that activates an interrupt. Now, whenever the sine voltage is higher than the forward voltage of the LED inside the optocoupler, the transistor is turned on, and connects the Arduino pin to ground. But, when the sine voltage is near the zero-point, the LED turns off, as well as the transistor. And, the voltage at pin 2 rises, which is basically the zero-point indicator. And after connecting the gate of the triac to another pin on the Arduino through an additional optocoupler, we can write an interrupt function that compares the measured temperature to the set temperature, and thus either turns on or off the triac depending on whether the set temperature was reached. The temperature measurement itself and the update of the display also repeats every 40 half-waves. Now, in theory, this code should have worked without a problem, but real life is not always that easy. While the iron does heat up, it seems to always measure the wrong temperature after every 40 half-waves, and thus lets the full [41st wave?] not pass. Afterwards, though, it gets the right temperature, and is back to normal... ...only to repeat the same mistake 40 half-waves later. In a nutshell, it means that it takes twice as long to heat up, which is around 24 seconds in total. But, nevertheless, once the target temperature was reached, it holds it pretty stable. So as a finishing touch, I added a second *ECHOING VOICE* FULL-BRIDGE RECTIFIER, with smoothing capacitors, to the 9V output of the transformer to power the microcontroller, and replaced the Arduino Nano with an Arduino Pro Mini. Before gathering the required components for the circuit, though, and connecting them to one another on a piece of perfboard, I used the free EasyEDA circuit design software to create an appropriate schematic. And, of course, you can find the schematic, along with additional project information, as always, in the video description. Once the circuit was complete, I designed an appropriate housing for all the components in 1-2-3D Design, printed it as three separate parts, which took around 20 hours in total, and started assembling the soldering station by mounting the transformer to the bottom of the case with an M5 screw. Afterwards, I soldered the transformer's mains voltage input to a switch which, on the other side, connects to a fuse, and the mains voltage connector. Once I secured the power input/switch to the case I continued by attaching the OLED LCD inside the upper section of the housing as well as the potentiometer. To finish the project, I guided the 15.5V and 9V wires into the upper section of the housing, as well as the soldering iron wires that entered through the front of the lower case connected them all to the circuit, attached the potentiometer and OLED LCD wires to the circuit as well, and closed it all up. And, just like that, you can create your own soldering station. I hope you liked this video! If so, don't forget to like, share, and subscribe, Stay creative, and I will see you next time!
The fact that the temperature was measured wrong after 40 half-waves somehow instantly reminded me of this
Proof Flashbacks intensify :0