RT Soldering pen

Soldering pen for Weller RT tips with OLED display

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Every hardware hacker need good soldering tool. My idea was to build own but with very specific qualities. On one side not so expensive, on second side high quality and also small with precise control and features.

I found some projects where is used Weller soldering tips designed for WMRP soldering iron with standard 3.5mm jack and inside the tip is also thermocouple for sensing temperature. These tips are not so cheap but the quality is really great, especially for fine soldering.

Hardware design is based on similar projects but with some modifications and improvements. Also my request was to make the hardware small as possible to fit into handle and capable to supply from hobbyist LiPO battery.


  • very compact - will fit into handle
  • display show status, preset and tip temperature, power, supply voltage, drop, ...
  • two buttons
  • automatic standby
  • sensing supply voltage and tip current
  • precise regulation with PID (PSD controller with some modifications)
  • supply voltage is from 5V to 15V (best is above 10V)
  • designed to supply from LIPO battery 2S (7.4V max is about 18W) or 3S (11.1V max is more than 40W)
  • calculating consumed Wh
  • heat-up in 5sec from 25 to 400°C (with 40W limit)
  • Idle current about 8mA

What is planed:

  • case
  • battery monitor (warn when battery need charge)
  • configuration editor for some constants from PSD controller, power limit, ....
  • open-source everything


Portable Network Graphics (PNG) - 64.37 kB - 03/30/2017 at 19:45


  • 1 × STM32F031 Microprocessors, Microcontrollers, DSPs / ARM, RISC-Based Microcontrollers
  • 1 × AD8551 Precise operational amplifier
  • 1 × ACS711 Hall effect current sensor
  • 1 × LMR14203 Power Management ICs / Switching Regulators and Controllers
  • 1 × OLED display 0.91" 128x32

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jaromir.sukuba wrote 03/26/2017 at 19:49 point

Do you have some more details available? Like, PCB design, firmware.I have some RT tips and I'm interested in building controller for it - this one seems to be perfect fit.

  Are you sure? yes | no

electrobob wrote 03/26/2017 at 15:41 point

Really nice work. I think this is how the future of soldering irons should be, just get rid of the classical station box. 

Why the accelerometer?

  Are you sure? yes | no

vlk wrote 03/26/2017 at 16:37 point


Accelerometer will be to wake up from stand-by

  Are you sure? yes | no

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