Arduino Auto Mixing System

“Get this one its way cheaper. The white wire on the four wire cable is the lambda out. Its all you need.”

Thanks Matt, Actually when you convert to Canadian dollars and add freight, the price is about the same.
That’s what started my search for possible newer alternatives


Yes there are a number of threads on the vacuum mixers. I have had the Sensors come bad in a the box but I have never seen a new one fail ever.

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So Matt, In the unit that you pointed out it seems the fancy signal conditioning and 0-5v conversion is done inside the gauge housing.

Where do you tap into the 0-5 voltsand ground for the arduino Analog/ground pins?
Just splice into the harness? or perhaps there’s a screw terminal on the back of the gauge that I can’t see?


Ahhhh … Sorry, I see you made reference to the white Lambda wire.



The white wire on the four wire cable that plugs into the gage is the 0-5v signal wire

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The Bosch sensors by themselves cost more than a $130 bucks. Thats the expensive part not the gauge or the controller.


I saw my name in the other threat and want to keep that one clear. At the moment I am fighting to get the exhaust clear with a scrubber and e-filter. Looking for some time to build another filter. Scrubber is out for the moment. Then next step is the engine running and then finally woodgas. And if I ever get at that point, the feeling is more important then the automation. You first need to get the feeling what is going on, next step might be automation, not the other way around. My generator will be full load all the time so I doubt I need an automixer. Way simpler system.


I don’t know much about this stuff, but here’s what I found. a/f ratio gauge for sale | eBay

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@ Al Frick,

Yes, those are the kits we are talking about.
I noticed in the listing that the Chinese are now making a copy.
They even put the AEM logo on the gauge. $99 for the whole setup.
Quality questionable.??

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@ Matt

Great tutorial you published.
My understanding is that the Bosch sensors put out a signal that is not 0-5vdc but something entirely different, and a signal conditioner is needed to convert that reading into a 0-5vdc voltage that the Arduino can understand. Where in the AEM kit does that conversion take place?


Can we wire a Bosch O2 sensor directly to the Arduino?
Eliminating the need to buy the full AEM Gauge/Harness assembly ?


The O2 sensor plugs into the back of the gauge. Then there is a four wire connector that also plugs into the back. Two wires are for the 12 volts in to power it. The blue is hooked up to the light switch for night time viewing and then the white wire is the 0 to 5 volts output.


Well lm guessing this is the problemwhy narrowbands dont work directly.

If you set the manual air control on stechiometric the values are all over the place and its probably wery comfusing for the Arduino. It sure is even for a human operator if you dont know whats going on. But what l was thinking is that in real life, noticable performance problems start to apear past those point on the graph

Culd we teach our Arduino to only act when numbers get in to the "bad zones?


In the field of maintaining a certain value, the most widespread and also the most effective method is the PID controller, where the response to the error (amplification of the process) is determined with the P element, the I element (integral) eliminates the static error after time and the D element (differential) does its job work already before the error would occur (if I compare it to catching a ball, where we start to withdraw our hand and close the palm before the ball touches the palm)


Just a suggestion.
Muscle wire might be used as a very low cost actuator to control butterfly valves. Here is a video I made.


Kristijan, correct me if I am wrong please, bus those graphs belong to a petrol engine. I believe woodgas operates somewhere around 8, where a narrowband doesnt work at all. Again, I have the least experience in this field.

Tone, you will have no problem organising a PID system. Me? All goes through the roof. Long, long time ago for me…I still understand the basics, but real life? I will stick to steppers and forget servo drives.


My head is starting to hurt. My poor peasant mind is not built for this :smile: l think l will back off.

Joep, what you ment with 8?

Yes, the graphs belong to a petrol engine but the curve is the same. When l set my Mercedes for city drive, the sensor wuld show about 800mv. If it fell below 250mv, l lost power. Dont hold me by the word on numbers, it was a long time ago, but its balpark.


My code is set up to do just that. There is the “happy window” where there is no need to correct. Once outside these parameters are the bad area where the controller responds and tries to get back the happy window :slight_smile: How fast it tries to get there is determined how far away it is from the happy window. The farter away the faster it runs; the closer it is the slower it runs. This program is very stable and is a PID loop.


I am not really up to date, but when reading Ben’s book I bought one and played a little. I think I read somewhere that the readout on wood was not the same as petrol. If there is some time this weekend I will do another search. The plan was to use it on the Atmos boiler for further improvement. The gauge that came along didnt read anything. The boys confiscated it and use it for adjusting the scooters :grinning:


Good article, Tone!
Her most important conclusion (for me): if an oxygen sensor is used in your system, then sooner or later, but inevitably, it will be damaged. :frowning: