This Soldering Pen Board with Audio Jack Supports Weller RT Tips

The 3.5mm audio jack may be slowly disappearing from new mobile phones, but I’ve recently discovered they were also used in some soldering irons such as the upcoming TS80 USB soldering iron succeeding TS100 model.

I initially thought it was a custom design from the maker of TSxxx soldering irons, but this morning I’ve come across the “RT Soldering Pen” board which also features a 3.5mm (audio) jack and can be used to make your own soldering iron by 3D printing your own enclosure, adding some power source, and inserting one of the many Weller RT tips available into the jack.

Soldering Pen Board Audio Jack
Click to Enlarge

RT soldering pen board specifications:

  • MCU – STMicro STM32F031 Arm Cortex-M0 micro-controller
  • Display – 0.91″ OLED display with 128×32 resolution
  • Compatible with all Weller RT tips with 3.5mm jack.
  • Set-point temperature – 20°C – 400°C with about +/-5°C accuracy (calibration is planed)
  • Maximum measurable temperature – 500°C
  • Heating speed – 30°C to 300°C in about 4s with RT-2 pen and 40W limit
  • Maximum heating power – Limited to 40W by software or by supply voltage: 40W @  11V, 20W @ 8V
  • Power Supply
    • Supply voltage – 5 – 18V (recommended: 7 – 15V)
    • Supply current
      • Idle – 15mA max
      • Pulse with peaks to 6A @12V (average resistance of RT heating elements is 2 Ohm, so current depends on supply voltage)
    • Regulation: PSD (PID) regulator with PWM power transfer (150ms period)
DIY Soldering Iron Pen
DIY Soldering Iron – Click to Enlarge

The board can be programmed with any ST-Link SWD programmer, and the firmware source code, binary release, and some documentation can be found in Github. Pavel, the developer, plans to implement left handed mode and add Fahrenheit units support soon.

Hardware resources including the main of main components and the schematics (PNG only) are available on the project’s page.

DIY Soldering Iron Case
RT Soldering Pen with “Tube” Case

But what’s about the case? There’s none for now, so you’d have to design your own, or like Pavel did, use a ø 10 mm transparent shrinkable tube. That does the job, and it’s inexpensive, just remember to peel off the OLED display protective film before  putting the tube on 🙂

Here’s the soldering iron in action.

The RT soldering pen board can be purchased on Tindie for $54 plus shipping, It is not sold as a kit, so that’s the board only, and you’d need to add your own Weller RT tip, power source, and case.

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5 years ago

I’m quite happy with my TS100, and it’s usable on batteries, which is excellent for hacking on the garden table when it’s sunny outside (the only problem is its 2.5mm DC jack which is too thick for most power blocks and requires a 2.1-to-2.5mm adapter). I also thought that an easier way to plug/unplug the tip would be nice, but I never thought about using an audio jack for this. I’m a bit surprised it supports that much current and was even less aware that it was already being used by some vendors like Weller. With that said, this project… Read more »

5 years ago

what happens when connecting headphones?

5 years ago

Good article. I love the link to Mario Reps. Those videos are always good! I saw this a week or so ago on his channel and was pretty impressed by the TS80. While this board looks good, the other exciting feature of the TS80 is that the input is a micro-USB connector and that is support QuickCharge powerbanks/chargers as power sources. That makes power supply trivial and easily portable. The 24V requirement of the TS100 (for full power) is a bit of a pain and the 5.5×2.5mm connector is huge and leads to an akward feel in the hand. I… Read more »

5 years ago

The 8W one is too small for anything but the tiniest of work. The other one is a standard heater type and suffers from poor temperature regulation. The big benefit of these newer integrated element/sensor/tip irons is that they can maintain much better regulation of temperature which gives them a much higher effective power. It’s a better thermal transfer design. The TS80 is just an improvement on the TS100 as the tips are better designed and they’re better mechanically–they are shorter which means they fit the hard better and make soldering easier.

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