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Open Source LSU4.9 Wideband Controller 
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TO220 - Visibile

Joined: Mon Jan 11, 2016 11:26 am
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I like the Op-Amp idea, I'm sure it'll need testing, but the concept you put forward sounds good to me.

The MCUs work is then limited to simply providing the heater, reading the current and reading the vgnd voltage (for greatest accuracy, don't assume 2.5V).

I'm yet to buy O2 sensor, was going to do the PCB first.


Sun Jan 31, 2016 12:42 pm
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QFP80 - Contributor

Joined: Wed Oct 01, 2014 7:06 am
Posts: 39
looking back into some of the shems for the old analog design, the original DIY_WB, a design adopted ( or designed? ) by Tech-Edge, it also employed a PID loop control over the IP current. It just did it with op-amps rather than a micro-controller. So, im starting to think that a "simple" op-amp circuit may not be enough to get the job done, else they would have done just that.
However, the analog circuit is still appealing to me for a few reasons.
I built a few of those DIY_WB boards back in the day, as well as displays using LED bar graphs, it was all analog.
hours spent tuning with these i started to notice a very peculiar "bug", sometimes, under the right conditions, the LED display would wig out due to very rapid full swing oscillations from the output of the WB controller. Instead of just the appropriate LEDs being lit, every LED would come on dimly as the voltage from the WB controller "banged against the rails" so to speak.
What i came to realize was this was not so much a bug, but Pre-ignition or detonation from the motor. The WB could tell me if i was detonating visually well before my ears could hear it.
This became an invaluable tuning aid, and something that was lost when i moved to the cheaper, microprocessor controlled LSU sensors.

So, i am wondering now how hard it would be to:
A, modify the NTK circuit to use the LSU sensor, and
B ,integrate some form of logic control on top of the analog circuitry to control the O2s temp.

Im thinking modifying the circuit to work with an LSU sensor is not terribly hard, im pretty sure its been done.
Adding logic control to monitor heater temp should be possible as well....


Mon Feb 01, 2016 8:00 am
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TO220 - Visibile

Joined: Thu Nov 20, 2014 4:06 pm
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Location: Omsk,Russia
This is my schematic of WBO controller. without pc interface.
The main feature is Pump cell drive method. I pump constant current in and out cell, then measure duty cycle of pulses, it gives me medium current value, and lamba calculated from look-up table of sensor's datasheet. There is setup photo just few posts above.


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Mon Feb 01, 2016 8:11 am
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You sure it was detonation and not lean, rich, or any other type of misfires? Misfires cause full lean and would rail your wideband. Preigntion/detonation shouldn't alter the mixture seen much unless bits of soot fall off or bits of metal start coming out :-D Especially not light pinging which is par for the course in many knock limited NA cars where you can go there briefly without total destruction.

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Mon Feb 01, 2016 8:24 am
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TO220 - Visibile

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Perhaps it was going rich / lean so fast that persistence of vision came into effect with the LEDs?


Mon Feb 01, 2016 8:39 am
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TO220 - Visibile

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Subver,
Thanks for the schem.
That format of schematic is difficult for me to read though

Missing from it is the base to ground resistors on the FETs? Without them, won't they float and when floating they can switch rapidly and cause the FET to overheat / melt??


Mon Feb 01, 2016 8:48 am
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TO220 - Visibile

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Location: Omsk,Russia
toc wrote:
Subver,
Thanks for the schem.
That format of schematic is difficult for me to read though

This is russian state standart format, GOST :)
FETs driven by MCU, pin configured as active output.


Mon Feb 01, 2016 9:10 am
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A weak pull down like 100k is still wise to have in case of the firmware not being healthy or being dead, it ensures the FETs are off, as if they're logic FETs they could just drift to being hard on instead.

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Mon Feb 01, 2016 10:02 am
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QFP80 - Contributor

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it was definitely a persistence of vision issue causing all the LEDs to appear dim.

My first thought when it initially happened was that it was a miss-fire ( lean missfire ) issue, however i quickly ruled that out,

i richened up the mixture, however this did not cure the issue, and with further observation i decided that if it were a lean miss, it should not indicate a full rich mixture.

There is no way of knowing exactly what was going on, that was in the days before GO-PRO and good cell phone cameras. I would have liked to get a good video of it.

It still may very well have been entirely related to a simple missfire, however at that time there was talk on the MS forums about active knock detection by measuring the ionization inside the combustion chamber by using the spark plug as a sensor... Dont think that it ever turned into anything, but there were some interesting papers linked that explained why detonation caused some form of ionization in the combustion gasses.

My thought was, that possibly this is what i was seeing. Like i said, without a much more elaborate testing procedure its impossible to tell.
And in reality i didn't care, as soon as i saw that condition i knew i needed to back the timing off a few degrees. Very handy.

Its fairly academic, the DIY_WB and the TE_WB v1.0 were basically identical, and the schems are still out there, though the TE_WB have a copy write on them
( not sure the legalities of using either one ). Both would be quite inexpensive to reproduce, however the main fault with that circuit was that it lacked any real Temp control.

While i still intend to play around with it, the Open source wide-band from 14point7 is probably the most logical system to start with. Its cheep, very few parts, and all of the hard work has been graciously donated. I have one of the kits, though i haven't had time to put it together yet, i just ordered a chip and a programmer from cypress this morning. My thought here is rather than spending a lot of time fine tuning an arduino based digital design, why not start with a proven digital controller that uses a modern 32 bit PSoC? the end result is still a digital controlled O2, but the PSoC has many advantages over an 8 bit micro for this aplication.

I still intend on playing with the anaolg just for kicks though.


Mon Feb 01, 2016 5:03 pm
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TO92 - Vaguely active

Joined: Sat Feb 13, 2016 9:32 pm
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Wow, great thread guys! Tons of info here. I'm new to the group and have a desire to do basically the same project (LSU 4.9 + Arduino). Just starting to wrap my head around the original (Hell Fire's) schematic, but I also like Joey's analog/opamp concept. Looking forward to seeing where it goes from here. Any updates on the prototyping or "must do" edits to the Hellfire schematic on the first page of this thread?


Tue Feb 16, 2016 2:34 am
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