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For any add-on boards such as VR conditioners, optos and OEM interface boards
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By ruzki
I´ve made a very naive approach of designing a Lambda controller board wich is based on a Bosch cj125 chip.
The board will be soldered to an Arduino Nano.
At the current state it has one PWM driven analog output and 2 DAC´s.

We ordered 10 pieces of PCB and will start testing this Board soon.

It would be great if somebody could take a look at the code.
Maybe in future this code could be implemented to the Speeduino code.

All KiCad project Files can be found here:

Let me know what you think.
Nano_Lambda.jpeg (157.36 KiB) Viewed 11119 times
UPDATE 10.04.2020

The Arduino based Nano Lambda Board has been extensively tested and is working as expected.

Alfagt has made an superb firmware for the Nano Lambda which can be found here:
For my understanding, there is no Controller out there with such extensive adjustment capabilities.
Via TunerStudio it is very easy to connect and tune. One can tune the analog outputs to compensate non linear behaviour and offset error.

tooly made an very convenient and easy to build Board named BL49SP. It is an 2-Layer Board with components only on one side, which make it also inexpensive to build. The Gerbers Files as well as Schematic can be found here:

Alfagt made an non open source Lambda Controller based on his firmware and improved hardware -BL49 by tooly- which has an extensive set of CAN functionalities as well as extended configuration options which I think are unique for an Lambda Controller. For more information check this Link:

Please post a comment or picture if you have build one Nano Lambda or BL49SP Bard.
Last edited by ruzki on Fri Apr 10, 2020 6:37 pm, edited 1 time in total.
Hello flat4power,
the code will be published soon when it is running on this platform. Please give us some days as the boards haven't arrived at this moment.
Most of the code has been taken here: https://github.com/Bylund/Lambda-Shield-Example
When it is running, everybody is invited to bring in his own ideas. I'm seeing a multi-Lambda-Controller on a Selfmade AVR Board for example (with two or four WB Controllers).
Best regards
This looks very interesting. What data do you have about driving the sensors?

On this layout, you might have problems with the heater current switching interfering with the other signals, as they have a shared GND across the board.
Might not be a problem, but if it is try connecting your +12V & GND power connections directly at the heater end of the board.
Made a very stupid mistake.
I´ve used a wrong footprint for the CJ125 :roll:
Nano_Lambda_FAIL.jpeg (149.88 KiB) Viewed 10856 times
i am not sure about your question.. We have got an old 40 page datasheet for the CJ125 chip. This is our basis.
Yes, there is a very good chance this will happen. Thanks for the advice! We will try like it is right now and will report.

Thank you very much Christian.
I´ve tested the first running Prototype this weekend.
So far things are looking good, lambda values seem to be plausible.

- Pinout is different compared to Arduino Uno.
- UBAT_MIN was set from 550 to 400 due to different resistor values for Battery voltage ADC

- Footprint for Diode U4 is wrong, diode needs to be turned on the PCB(already changed on GitHub)
- Digital Voltage Output via Op-amp seems not to work

Now we will have to tune the Arduino sketch.
y%X1Iw6aQH6T2IaWXMDddg_thumb_115b6.jpg (302.71 KiB) Viewed 10642 times
sjevPvmTTRyGXvqY5mSkFA_thumb_115b5.jpg (303.2 KiB) Viewed 10642 times
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