Open Source LSU4.9 Wideband Controller

Free Open Source Hardware discussion forum. Post your Free Open Source hardware projects here!
toc
TO220 - Visibile
Posts: 13
Joined: Mon Jan 11, 2016 11:26 am

Re: Open Source LSU4.9 Wideband Controller

Post by toc »

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.
joey120373
QFP80 - Contributor
Posts: 39
Joined: Wed Oct 01, 2014 7:06 am

Re: Open Source LSU4.9 Wideband Controller

Post by joey120373 »

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....
subver
TO220 - Visibile
Posts: 6
Joined: Thu Nov 20, 2014 4:06 pm
Location: Omsk,Russia
Contact:

Re: Open Source LSU4.9 Wideband Controller

Post by subver »

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.
Attachments
wbo.png
User avatar
Fred
Moderator
Posts: 15431
Joined: Tue Jan 15, 2008 2:31 pm
Location: Home sweet home!
Contact:

Re: Open Source LSU4.9 Wideband Controller

Post by Fred »

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.
DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!
toc
TO220 - Visibile
Posts: 13
Joined: Mon Jan 11, 2016 11:26 am

Re: Open Source LSU4.9 Wideband Controller

Post by toc »

Perhaps it was going rich / lean so fast that persistence of vision came into effect with the LEDs?
toc
TO220 - Visibile
Posts: 13
Joined: Mon Jan 11, 2016 11:26 am

Re: Open Source LSU4.9 Wideband Controller

Post by toc »

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??
subver
TO220 - Visibile
Posts: 6
Joined: Thu Nov 20, 2014 4:06 pm
Location: Omsk,Russia
Contact:

Re: Open Source LSU4.9 Wideband Controller

Post by subver »

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.
User avatar
Fred
Moderator
Posts: 15431
Joined: Tue Jan 15, 2008 2:31 pm
Location: Home sweet home!
Contact:

Re: Open Source LSU4.9 Wideband Controller

Post by Fred »

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.
DIYEFI.org - where Open Source means Open Source, and Free means Freedom
FreeEMS.org - the open source engine management system
FreeEMS dev diary and its comments thread and my turbo truck!
n00bs, do NOT PM or email tech questions! Use the forum!
The ever growing list of FreeEMS success stories!
joey120373
QFP80 - Contributor
Posts: 39
Joined: Wed Oct 01, 2014 7:06 am

Re: Open Source LSU4.9 Wideband Controller

Post by joey120373 »

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.
CarlH
TO92 - Vaguely active
Posts: 2
Joined: Sat Feb 13, 2016 9:32 pm

Re: Open Source LSU4.9 Wideband Controller

Post by CarlH »

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?
Post Reply