RT Soldering pen

Soldering pen for Weller RT tips with OLED display

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vlk has 105 orders / 7 reviews
Ships from Prague, Czechia
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 many 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.Buy one on tindiy:


  • 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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ivan003003 wrote 06/29/2018 at 14:02 point

Hello there Mr.vlk

I have read carefully the technical characteristic of your RT Soldering pen.

I'm really in love with it and i'm very excited to buy it,at least one :)

However,for me the only one problem is this : 

i can't go to buy this item raw as it is now!

without any kind of enclousure and an incorporated power plug.

I really hope that you & Otto Winter will release the RT soldering pen in final version,with the enclousure and the incorporated power plug.

Thanks you very much !

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vlk wrote 07/08/2018 at 05:37 point

Hi Ivan, enclosure is planed

  Are you sure? yes | no

ivan003003 wrote 07/10/2018 at 17:47 point

I'm very,very glad :)

  Are you sure? yes | no


[this comment has been deleted]

vlk wrote 06/26/2018 at 10:46 point

No, it is not a clone, it is completely created from scratch (HW and SW), it uses different MCU, also have current sensor, for better diagnostic and more precise regulation and also it can operate at lover voltages, faster heating (4s). Also biggest advantage are Weller tips, and is made in EU. On other side there is no USB.

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Rens wrote 04/14/2018 at 00:09 point


very nice project, any plans to make the PCB available.

  Are you sure? yes | no

Albert Green wrote 03/14/2018 at 20:04 point

Are you using the I2C version of the 128x32 OLED display? Where do you buy it? I cannot find a source for it. seems to sell only the SPI version. And on Aliexpress/ebay the I2C version seems only available soldered on an adapter PCB.

  Are you sure? yes | no

vlk wrote 03/26/2018 at 06:15 point

Hello, there are also on ebay:

  Are you sure? yes | no

Bodzio wrote 02/15/2018 at 18:03 point

You have a bug in the project. Weller uses a D-type thermocouple in the tips no K-type !

K type thermocouple in 500 'C has voltage 20.644 mV, but D type 8,077mV.

  Are you sure? yes | no

vlk wrote 02/15/2018 at 22:45 point

Thanks! You right, The equation is hope correct, but the type of the thermocouple in schematic is wrong. I will fix this.

  Are you sure? yes | no

Otto Winter wrote 02/07/2018 at 16:25 point

It looks very good, if you get it running, please tell me, how can i get 1-2 finished PCBs!
Best Regards
Otto W.

  Are you sure? yes | no

Paulo Bruckmann wrote 02/06/2018 at 13:38 point

I'm amazed how you fit all in that size, I am guessing you used 4 layer board. I'm designing  one for Arduino with usb ,accelerometer , buzzer (take a look at my profile).  My problem is that  a ts100 for 45$ and I I'm aware that is not the same thing. But this is the price of one RT tip :/ . 

  Are you sure? yes | no

vlk wrote 02/06/2018 at 19:13 point

Hi I saw your version, nice renderings and also case.

Regarding PCB, yes! it is 2 (TWO) layers, design was not easy and I spend lot of time optimizing for high current. Most problematic was ground to keep it strong from one side to another.

TS-100 is nice, but Weller tips are TIPs and if anyone at least once tried Weller then he know that soldering with that is quite different (better). TS-100 is also heavier and bigger, tip is also longer and not so good for very precise soldering. Also need higher voltage for work. (for RT only 12V with 50W and is working from 7V with 18W)

Cheapest Weller station cost more than €300 ?

RT tips are in discount, so the price is now quite better.

  Are you sure? yes | no

Paulo Bruckmann wrote 02/06/2018 at 19:56 point

I don't own a weller RT tip yet, neither a TS100, but already worked with other weller irons. I wasn't sure if it is going to be a big difference. The parts and labour seemed to be an investment.
But now that you print me out the picture, I may continue the project. I always wanted a mobile friendly soldering iron.

Oh! It's 2 layers! You got skills, and I know what you talking about when you say optimizing! What was the minimum footprint, 0603s?  I may switch my 0805s resistors to 0603s. I also using the oled version of 11 pin

I let the power traces without solder mask so they get solder tinned in the fabrication.

I use kicad, if you have the all parts in 3D ( I designed the display) it renders in realtime, it's mind-blowing, isn't it? You don't believe it but my last board layout was built from scratch in less than 2 hours. push  & shove power! 

Thank you for your Reply . Regards!

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HP (@banjohat) wrote 02/06/2018 at 13:33 point

Interesting! This reminds me of my own project ;)
Out of curiosity - how did you end up with that mini-jack?

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vlk wrote 02/06/2018 at 14:38 point

Hi HP,


Yes I know your project, my is inspired by yours and also other similar projects (but desktop versions) and also by TS-100.

About JACK connector, I changed the connector to another because this one needs thin plated slots which was problem with many PCB manufacturers, or it was too expensive.

  Are you sure? yes | no

HP (@banjohat) wrote 02/06/2018 at 14:40 point

Very interesting! I kept that one because I really favoered the co-planarity of the connector. However, I haven't been able to find anything rated for 2A which is needed by the tip. I guess that's not a problem for you if you use another one - is that still co-planar?

  Are you sure? yes | no

vlk wrote 02/06/2018 at 18:47 point

The connector is and it has two spring contacts and also two pins for ground then two contacts and pins for TIP (heater) and one for mid pin (sensor) so, I think this will be better. So if one contact is rated for 1A then two contacts can transfer 2Amps. and I don't connect under high current, so static current can withstand much higher. Previous version with old connector (on picture) I checked with IR camera and the connector was cold, hottest place was BUCK converter, MCU and chip on OLED display.

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René Arts wrote 06/26/2018 at 15:17 point

If you would want to improve the connector; I have found a nice one which is rated for 5A continuous: search for FCR1295 S9/BBB stereo 3.5mm mini jack socket, it is available i.e. at Conrad and Farnell. Nice project by the way, I'm thinking of buying one!

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solankidharmesh40 wrote 01/16/2018 at 20:12 point

just love this project 😍😍😍😍

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Makerdog wrote 12/31/2017 at 09:48 point

Vlk I want this thing, I hope it still in progress. Otto Winter, your Design is very beautiful I Love it 

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Otto Winter wrote 01/22/2018 at 22:26 point

Thx. ...unfortunately nothing going forward, it is still frozen :-(

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JK wrote 11/13/2017 at 19:44 point

Still any updates?

  Are you sure? yes | no

Jez wrote 07/10/2017 at 20:28 point

vlk... Any updates to this???

  Are you sure? yes | no

Paulo Bruckmann wrote 06/01/2017 at 20:32 point

Thank you for your inspiration, I am working in something similar with gyroscope, buzzer and usb port  

  Are you sure? yes | no

Paulo Bruckmann wrote 05/23/2017 at 22:02 point

Any update? What about a buzzer? 

  Are you sure? yes | no

Kees Hessels wrote 05/19/2017 at 19:12 point

Great idea, might be a good project to use Pyralux, so you can curve it to the casing.  Cool project, well done. 

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Muphins wrote 05/18/2017 at 11:49 point

This is AWESOME !

On the finished product you could even put a magnet to have a MagSafe-type power connection. Not sure if it would be really useful but at least it would be cool.

  Are you sure? yes | no

Chrischi wrote 05/18/2017 at 02:53 point

Isn't the Mini TS100 nearly the same? (

What differences to the TS100 are you want to archive?

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B4Me wrote 05/18/2017 at 06:56 point

More watts 

  Are you sure? yes | no

Chrischi wrote 05/18/2017 at 13:32 point

I like this Soldering Pen but the TS100 has 65W and i think this one 40W.

maybe Otto can clarify this.

  Are you sure? yes | no

René Arts wrote 05/18/2017 at 13:26 point

Being able to use high quality Weller RT tips, which are easy to change without the nasty burnt chicken smell ;-)

  Are you sure? yes | no

Chrischi wrote 05/18/2017 at 13:33 point


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jaromir.sukuba wrote 05/19/2017 at 14:26 point

Well, sometimes people like to build something for for the sake of creative process, not to outperform somebody else. It's called hobby and I'm kind of glad nobody questions value of raw paper in my stamps collection.

  Are you sure? yes | no

Chrischi wrote 05/19/2017 at 14:28 point

full ack. 

by the way if anyone misunderstand me, i LOVE this project.

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Aisha Farsi wrote 05/17/2017 at 23:22 point

I would definitely pay for one, or two, I really would.

  Are you sure? yes | no

Otto Winter wrote 05/01/2017 at 10:32 point

The 0.84 Inch Display has a resolution of 96x16 pixel (your Schematics specifikation)!
OLED Display with a resolution of 128x32 pixel is 0.91 Inch...
Witch is implemented?

  Are you sure? yes | no

vlk wrote 05/01/2017 at 15:14 point

Hello Otto, thanks for info, It is mistake caused by that I have one sample with 0.84" display 96x16 pixels and on pictures is version with bigger display 0.91"

  Are you sure? yes | no

Otto Winter wrote 04/30/2017 at 20:03 point

Hello Leuven,
can i bay the finished unit?
Best Regards owsuisse

  Are you sure? yes | no

vlk wrote 05/01/2017 at 15:22 point

Thanks for interest, I have some plans with selling this and I hope it will be soon.

  Are you sure? yes | no

Otto Winter wrote 05/20/2017 at 00:31 point

If you can give me the PCB dimensions. i would design a case for 3D printing or other manufacturing formats like molding or milling etc.
For prototyping is the best way 3D printing with Laser sintering technology.
You can see a preliminary picture here:

This is the Display area with two buttons to configuration.

With right click on the Pictures, "View graphic" you can see it in a full resolution!

  Are you sure? yes | no

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