Sean,
Thanks for the clarification on SBC schedulers. My only SBC exposure is to the PCduino, and I’m still getting my feet wet with it. I agree the teensy is a better choice, especially now that breakout boards are available for them which allows easier access to the center pins.
SBCs might actually work. Add the preempt_rt patches to the linux kernel, and that gives you the hard timers you need. With the preempt_RT patches, the interrupt reaction lag is < .25 milliseconds. Without the patches, you can still do a lot of traditional micro controller types of things as most things that use a microcontroller, can lag much more then that. To put it into perspective, 100x more then .25 milliseconds, is 25 milliseconds, or 25/1000ths of a second. So how accurate do you have to be… 
Thus the reason why it is a debated topic, and really a gray area.
Woodgas is using natural aspiration, the electronics are greatly simplified over using EFI. The ignition is probably the hardest part. And I should note somewhere in here, because of the magnetic field interference of the engine, everything needs to be shielded.
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Any updates on how well this mixture control has worked out in practice over the past few months?
Anybody trying this on a KG?
I’ve done tutorial on how to build one with a wide band O2 sensor. The code has been updated since, but it very polished and works quite well now.
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Where is the code written?
Btw fine job chum.
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I just briefly skimmed the code ( forgive me I am not a C programmer ).
From what I gather you set up a pair of upper and lower tolerable limits and then operate in a dead band.
A delay function prevent instability or overshoot undershoot.
My only concern is the DELAY command.
If I am not mistaken this halts the program steps and literally waits.
Did you tinker with this from the arduino library?
PID(&Input, &Output, &Setpoint, Kp, Ki, Kd, Direction)
Other useful pieces of codes I see could be.
SetMode(mode)
SetTunings(Kp, Ki, Kd)
SetControllerDirection()
In particular instead of wait maybe SetSampleTime(SampleTime)
Could speed up things.
Just throwing this stuff out there.
I have never used these commands and I am not familiar enough to say they will speed things up or improve stability.
However I have used somethings like RED LION and Foxboro single station controllers.
With so much processing speed and power maybe its pointless to worry about short wait times.
Far out question time:
Maybe a single station controller is the answer and leave the arduino out of it.
http://www.ebay.com/itm/Red-Lion-T-48-Series-Temperature-Controller-T481100-85-250-VAC-/111908276686?hash=item1a0e40c9ce:g:WdQAAOSwKtlWr4xY
Yes the delay at the end of the run is just for stability and is just 10 microseconds… The mapped delay however, changes almost instantly.
If it sees the sensor reading less than 650 or greater then 700 it will react. It the reading is in between these parameters than it does nothing.
The delay is mapped to those parameters and you can achieve from 0 on up to 3000 microseconds of delay in the delay function. So if the reading is at say 649 the delay will be almost at the max delay assigned as the readings go closer the zero the amount of delay follows this. So if you have a wide open throttle and it pegs out at 0 volts the servo will not have any delay and will respond at its maximum speed. In this scenario it typically will over shoot and this is fine and is actually desired as it gives it a chance to clear the rich condition created from loading. At this point it is now reading lean but I have the start delay at 800 so it creeps back into to the safe parameters without over shooting.
No need to fix this code it works.
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I may be able to eliminate the void set up code. This was for previous code and I was having an issue with the servo moving during transition from manual mode to automatic. But I think now this may not be an issue Ill have to try it and see what happens.
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Thanks for sharing Matt.
I am in process of deciding how I want to set up my controls and instrumentation.
At this point in life, I am pretty addicted to KISS and fully manual systems.
IMO, proprietary systems and secretive vendors in collusion with politicians (read OBDII etc.) have just about ruined automobiles.
On the other hand, I am attracted to the open source hardware and software community, and can see where these tools can genuinely make systems better AND less expensive (discrete instrumentation, alone, adds up, such as thermocouple displays, etc.)
So, I am toying with the idea of incorporating some arduino technology from the outset, at least for sensor read-outs…
This is one of the obstacles of gasification, getting an engine to run it without intervention. This is one of the tools that will be a major help especially on systems that do not have very linear gas flows. So this and the grate and hopper timers Ive put out here for you all.
With all three of these systems the more reliable the machine becomes. The grate and hopper agitators really help keeps flows linear and prevents other issues from occurring. These two systems are not corrective action, they are preventive measures. Once you have the gasifier breathing and flowing consistently the fuel mixer can then run with less effort. The loading of the generator is where this is really handy you can not do this manually like the arduino it positions valving very fast with precision.
The other thing is because this is open sourced and the tools were given to me for free i dont have an issue giving back.
Some of the stuff we do is our technology though and we really don’t have a choice but to keep it protected at this point. Especially upcoming technology, If we don’t get it patented someone else will and it can be turned on us. Its a cruel world sometimes.
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Yes. I am in complete agreement with everything you said.
And certainly, for unattended operation for longer periods of time, this sort of technology is a must.
As far as your proprietary technology, I don’t have a problem with that. What I DO have a problem with is vendors colluding with the state to further their rent seeking through law and regulation.
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I think I have the mixer controller as good as it will ever get. It does what the input signal tells it too, and is responding as it should. There is a loping at idle and light loading, I was watching the governor response and it is really fast. So Ive been trying to think of a way to slow that response down and I thought of something today. I put a small air cylinder on order today with flow control valves. I’m going to hook this up the throttle linkage of the carburetor. This should dampen the movement and I will have full control over this with the flow controls on the cylinder. This shouldn’t change the rpm setting as this wont have any additional spring tension.
I think this will greatly enhance the mixer control and allow to operate much smoother.
But even without the mixer unit, for those that are using manual adjusted valving, this may help a lot on those applications as well.
Just wanted to share NH Nbbylogger’ s video of the O2 mixer controller. He is using my most recent code version and implemented it pretty close to the tutorial I did a few years ago. This system is very solid and will give you the ability to walk away from the machine with out the anxiety of the engine stalling. The guys at Argos last year that saw the machine I had there. May have noticed I left the machine run and walked the fair grounds only to return for refueling. I think it ran for a total of 8 hours on Saturday mostly unattended. 
This would not be possible with out this controller, at least not on any machine I have ever built.
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Hello Matt,
Great job you did there.Please let me know if you finalized your code for the fuel/air mixer valve.
Probably you don’t need this but there is a great collection of servo valves 3d printed cases.It can simplify things.
By the way, you are the reason that I got motivated to start learning arduino.You can easily install many things in your gasifier, like sensors and thermometers.
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THANK YOU…
ITS an ambition of mine to do AFR control more than ever now I have been working with my arduino kit so not totally in the dark…
My 15000 watt onan is happy on wood gas but also becoming a pain because i am constantly having to adjust the mixer valve…
My set up can be seen at ushillbillies on YouTube…
Tom Lambert.
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Onan green right?
Looks to be a flathead four cylinder, eh? 'Aught to keep your A-car blood stirring.
Very glad you’ve pushed trough to a system able to give you needs-must use.
Do’n hasta’ be perfect, or brainac ideal. Just get the job done. On your own woods.
Regards
Steve unruh
Oh. On those Honda fuel sipping 2000’s best to only fuel add through a painters filter cone. Even plastic thread cap slivers from a can have, had me also carb dropping and back blowing clean. And metals cans internal moisture sweat is a real engine stopper for sure. The price you pay for a 1/10 gallon (US) an hour flow systems. 380 ml an hour?
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The fiat 2 cylinder had hydraulic operated engine valves . Oil does not bend or break .
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Speaking of bending and breaking… For anyone using hobby servos in their projects:
Metal gears are great for durability but another common failure mode is the servo’s potentiometer going bad. The potentiometer is a little variable resistor that sweeps a contact point, a brush, mechanically across a resistance surface to measure the angle of the servo shaft. For this reason they can wear out and resistance values can drift. For a hobby RC car’s steering that doesn’t really matter but for other use cases it may.
If you have hundreds or thousands of dollar in a project it’s worth considering a digital servo. In a digital servo the mechanical potentiometer is replaced with a contactless sensor that works equivalently. We are talking about $20 a servo vs $5. In many/most cases I’d spring for the extra $15: e.g. check out DS3218MG which is a rock solid digital alternative.
[edit typos]
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Just an idea I had. What if a control knob were connected to a strain gauge, and the output routed through a power amplifier. Voila, low noise audio volume control.
Rindert
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