We talked about it a few months ago [Electronoobs] he was working on his open source alternative to pocket thermal welders like the TS100. Powered by the ATMega328p microcontroller and using a 3D printed casing, its version could be built for as little as $ 15 USD depending on where you purchased your parts. But by its own admission, the design was held back by the quality of the spare $ 5 replacement tips that it designed around. As the saying goes, you get what you pay for.
But [Electronoobs] is back with the second version of its portable do-it-yourself welder, and this time uses the decidedly HAKKO T12 tip. Since this tip has the thermocouple and the series heating element, it has involved a fairly large redesign of the whole project, but in the end it was well worth it. After all, a welder is really as good as his tip to start with.
This version of the iron eliminates the MAX6675 used in V1 and replaces it with an LM358 operational amplifier to read the thermocouple in the tip of the T12. [Electronoobs] then used an external thermocouple to compare the output of the LM358 with the actual temperature at the tip. With this data he created a function that returns the tip temperature from the analog voltage.
While the physical and electrical elements of the tip have changed substantially, much of the design has remained the same as the first version. In addition to the ATMega328p microcontroller, the 2.0 version of the iron still uses the same OLED 128 × 32 I2C display, MOSFET and 5V buck converter of the original iron. That said, [Electronoobs] is already considering a third revision that will make the iron even smaller by replacing the MOSFET and the buck converter. It might be better to consider this an intermediate step before the do-it-yourself iron takes its final shape, which we are very interested in seeing.
The first version of the DIY Arduino welder has attracted a little attention, so there seems to be a decent number of people out there who are not content to throw down the money for the TS100.
[Thanks to BaldPower for the tip.]