Carlazar posted pictures of his simple soldering iron driver (SSID) with Arduino PID control in the project log forum:
Main features are:
– Any thermocouple type irons.
– Additional control mode: On-Off controller (besides PID PWM).
– External power supply: Some standard Notebook power supply DC 19V, 4.74A.
– Small dimensions: It fits into 90mm x 110mm x 45mm (WxDxH) box.
– Easy to assemble.
– Simple design: only a few components (besides Arduino).
The HQ soldering iron HQ20/HQ30 (24V, 48W) was used. It has the E-type thermocouple built in (68uV/degC) but you can change that value in software according to the soldering iron that is used (for example K-type is 41uV/degC).
Isn’t it suboptimal to drive soldering irons with DC current? Something about electromigration causing early failure of the heating element? I guess its not serious problem because the elements are rather inexpensive. Just be sure you have a backup soldering iron to fix your soldering iron.
What is suboptimal here is that 19v are used instead of 24, all of those irons are 48W at 24v (2A/12Ohm) so from a 48W iron you get a 30W iron… The DC current does degrade the heating element, but if you are building an soldering iron from an Arduino, you are not gonna use it enough to feel the difference.
Can you explain – why the DC current degrade the heating element ?
My guess is electromigration. With very high DC current density, you get physical void formation over time due to momentum transfer from the current-carrying electrons scattering off atoms. In most circuits this is negligible, but it matters in the tiny interconnects on modern ICs and, I guess, in filaments where high temperatures make it easier to displace atoms from the lattice.
How accurate is the temperature at the tip at temperatures below 100 deg C? Does it track what is displayed on the control box?
To flip: more like 2A x 19V = 38W