Update on decoder teeth amount?

[racingmini_mtl]

I would have thought that something with an option of /3,/4,/5 with some conditioners on board would work well.

From a few sums, the 9S08QG8 might be quick enough for the job of simply dividing the wheel. Logic chips, a counter and a latch might do it, but could end up more messy that a microcontroller.

James

If I were going to do it I'd likely look to combine the flywheel and reference teeth into one simulated (divided) crank pattern to feed to the Megasquirt. If a cam trigger is present this can feed the Megasquirt in the normal way.

James

That's funny because that's pretty much the same conclusions I came up with .

The same cam and crank signals can be used to run distributor ignition and COP on a 5cyl (as far as I know with my limited knowledge of MS1extra) so that would simplify things up (even if it's not the case, it's not a difficult thing to do).

So taking what has been mentioned above by James and Haudi, I'll have a look and propose something and give an estimate of what the cost would be. I may take Haudi's offer to help with breadboarding the circuit and testing it because I'm not setup to test it in a real situation. But I'd have to provide the programmed CPU for that.

Cheers,
Jean

[Haudi]

If the cost estimate stays arround $20 I'll put in for 5 initially. After some personal turmoil has cleared up shortly after the new year I would likely go for 5 more.

[Haudi]

http://www.frwilk.com/944dme/math.htm

That site shows a 944 as having 130 teeth, which doesn't work out, but shows a 944 Turbo as having 132 which divided by 3 is 44.

[thedge]

944 Turbos have 132 teeth on the flywheel. I made a divider using a 4017B chip, setup to divide by 3 for a 44+1 setup. The reference was used as a second trigger. It seemed to work fine while cranking, until the engine blew up (gouged out a cylinder wall ).


Heres a scope of the divider in action. The red is the output from a VR circuit (aka input to the divider circuit), the blue is the output from the divider.




Heres a link to the circuit diagram. I used the one on the right, count and recycle.

http://thedge.info/msefi/divby3/circuit34.pdf

[jsmcortina]

Unless the reset flywheel pulse is used to reset the 4017 surely you'll be random number of flywheel teeth in error. An OR gate might suffice.

James

[racingmini_mtl]

I now estimate that the cost would be about $25 for the board and the programmed CPU. The board would have the CPU, a voltage regulator (for the CPU), 2 VR circuits based on the LM1815, a Hall sensor circuit, and 2 outputs for the crank and cam signals. There would be jumpers to select the direction of the outputs and the mode. My initial estimate is that there would be 4 jumpers for the mode which would give 16 different modes. These modes still have to be established but would give the divider, which signals are used (crank, TDC, cam), and what output to produce (missing tooth wheel or not).

I'd like to know if that seems to make sense to those who need this in terms of cost and features. If so, I'll start working on the firmware and I'll finish the initial schematic.

There's one thing that I need to be clarified. Is there a need to have anything done to the cam signal for it to be used by Megasquirt? Because with the information I have now, this signal could just bypass the board completely and that wouldn't prevent the generation of the correct and synchronized crank signal using the flywheel gear teeth and the TDC signal. Two reasons to have the signal go through the board is if there is a need to have the Hall sensor circuit (but then it does not need to go through the CPU) or if the cam signal is to short to be used directly by MS1/extra. Also, if there is no TDC signal, then the cam signal could be used to synchronize the crank signal but that would require an accurate cam signal and could take a long time for the initial synchronization.

Jean

[Haudi]

The cam signal as I see it is a basic hall sensor in the distributor setup with 1 trigger per cam revolution, so unless I'm mistaken there shoudn't be any changes or such - just the straight forward hall sensor input circuit should do the trick. This is for the 5 cylinders, the 4 cylinders wouldn't need a cam signal at all just the TDC and tooth counter.

One constant on this setup for sure is the dual VR with TDC and tooth counter - the is no known application where they wouldn't be there, so no need to worry about using the cam signal for TDC in lie of flywheel TDC sensor.


One question I have for the masses... for testing purposes is it possible to split the VR signal between two devices? For example a nice test method would be to wire up this add on board to my MS (and the VR sensors), but only as a tach input for the current fuel only setup and let my cars stock ECU still run the ignition also using the VR inputs. I have all of the stuff to go COP or I could wire the MSnS to do distributor ignition, but it would be harder to tell if any issues are due to my ignition settings or due to the trigger being not quite right.

[racingmini_mtl]

The cam signal as I see it is a basic hall sensor in the distributor setup with 1 trigger per cam revolution, so unless I'm mistaken there shoudn't be any changes or such - just the straight forward hall sensor input circuit should do the trick. This is for the 5 cylinders, the 4 cylinders wouldn't need a cam signal at all just the TDC and tooth counter.

One constant on this setup for sure is the dual VR with TDC and tooth counter - the is no known application where they wouldn't be there, so no need to worry about using the cam signal for TDC in lie of flywheel TDC sensor.

Ok that sounds good. But just for future potential development and/or other applications, I've put jumpers to allow the Hall sensor circuit signal to either go to the CPU or go directly to an output. The firmware will not initially use this signal.

I have pretty much completed my initial schematic of the board so I can start on the firmware. I'll have to see if the firmware requires updating the schematic before being ready for testing. I'll post updates here.

Jean

[racingmini_mtl]

I'm still working on the firmware but I thought I should give an update. I haven't been able to put much time on it but should be able to do more in the coming days.

The plan is to have the 2 VR signals going to the CPU (through 2 LM1815 conditioners) to generate the crank signal. The divider for the crank signal will be chosen with jumpers and it will be possible to generate either a missing tooth wheel signal or a non-missing tooth wheel signal (selectable through a jumper). Of course, the non-missing tooth will require the cam signal for the MS to be able to do something with it. The missing-tooth signal will be usable with or without the cam signal (depending on MS configuration and version).

The cam signal will have it's own opto circuit with Hall sensor input and output to go to the MS board. The opto circuit will be configurable to be inverting or not and have a choice of pullups. It will also be possible to connect it to the CPU (with the appropriate pullup) through a jumper. As mentioned before, the initial firmware version will not make use of this but may be used eventually.

There will also be an auxiliary output that will be configured as a tach output in the initial firmware version. It will just be a logical output going to a transistor with a selectable pullup which will be sufficient for certain tachs but may not work for some which were originally connected to the coil. For those, an external additional circuit will be required. The tach signal will have the appropriate number of pulses per cycle depending on the mode selected (which also selects the appropriate divider for the crank signal).

The crank and tach signal will have jumpers to select if the signal will be inverted or not.

As you can see, I want this to be as configurable as possible so that the same board can be used in different configurations by just selecting the appropriate jumpers (some resistor and capacitor values may also need to be adjusted for the different configurations).

I should have a first version of the firmware in the next few days. I will test it as best I can on the bench (using a JimStim with modified code and a CPU demo board with the new code) but it will require testing with a real setup which I don't have. Once this testing has been done I'll be able to have the board made. I already have a layout done so this part should be pretty quick.

Cheers,
Jean

[Haudi]

Sounds great so far!

I never did find any info on sharing a VR signal to aid in any needed diag work.

As of current I've got the cylinder head off of my MS'd Audi, but getting it together by the time you are ready shouldn't be an issue.

[racingmini_mtl]

I've done some more work on the firmware and I'm almost there. I need some more testing and tweaking due to some hardware changes.

I have redone the board layout because I thought it was a bit more complex than needed. I now have only what I think is needed and it's still flexible enough for different configurations. I have removed the auxiliary output because this is already taken care of by the MS board/firmware and I have remove the possibility to connect the cam sensor to the CPU because it's not needed with the TDC signal. So with the reduced number of I/Os, I have changed the CPU to something with a smaller package (8-pin instead of 16-pin).

With those changes, the board can now be smaller (and cheaper): 1"x4" instead of 1.5"x4". It has also reduced the needed parts so the total cost will be lower: I think that the board+programmed CPU could now be $22 and a few more bucks can be saved from the fewer parts. The disadvantage is that there are fewer possible modes simply because there are fewer CPU pins available. There are 4 possible modes (2 jumpers) and 1 jumper for inverting the crank output. I was thinking of having the modes be: divide by 2, 3, 4, and 5. I was also thinking of always generating a missing tooth crank signal since all firmware can use this either with or without a cam signal (as far as I know). The modes could also be divide by 3, 4 and with/without missing tooth.

If someone feels that this version is too limited then I can go with the more complex solution. I just think that the greater flexibility (more than needed?) is more than outweighed by the lower cost and smaller footprint of the board.

In any case, I'm waiting for samples of the new CPU to arrive to complete my tests. Testing won't take long because it's the same CPU family as what I have now so I can test almost everything until then.

Cody, if you're still interested in doing some testing, I'll contact you later when I have things ready to see how we can proceed.

Cheers,
Jean

[Haudi]

Absolutely interested in testing, keep me posted ;-).

The less featured version sounds fair enough. Sometimes extra features are just too cumbersome and not needed. At some point if there is any demand at least the basics would be worked out so you can do the larger one if needed.

[racingmini_mtl]

The initial version of the code is done and bench tested and I have ordered a first batch of boards. Cody will do some in-car testing to validate the board and code.

I'll post the results of testing here. If you're interested in a board and programmed CPU, let me know. As I said in a previous message, the partial kit (board+programmed CPU) will be $22 plus shipping.

Jean

[thedge]

Does it still have the LM1815s on the same board? I think that was in the original design?

[racingmini_mtl]

Does it still have the LM1815s on the same board? I think that was in the original design?

Yes, it does. There are 2 LM1815 VR conditioner circuits and one Hall sensor opto-isolator circuit.

The board looks like this:


U4 is the opto-isolator and U3 is the CPU. The board measures 1"x4" so it fits in a slot of the standard MS case. There are also 4 mounting holes if someone wants to attach it to the case or fit it in another case.

Jean

[thedge]

Looks good!

[savagerocco]

I have my first board of two that Jean shipped to me built, and I have a built V3 MS-I ready to go. Will be making a harness for my car this week and hopefully get the car up and running this week too. Just to clarify, the car is a 1990 audi 90 20v sedan running an AAN 2.21L 20v turbo motor out of a 1995 S6. I have replaced the factory coils and POS modules with 1.8T COP units, so if anybody wants to chime in on the correct trigger settings for the sequnetial ignition firing sequence, feel free.

[vlopsahl]

Guess many of you already know this one, http://www.vems.hu/wiki/index.php?page= ... udiTrigger
Good info on the Audi 5-syl 20v 135-tooth, 3-signal trigger system. If all the testing goes well I will be interested in trying the board as well.


thanks
Vegard

[Haudi]

No fair, I haven't recieved my pair yet . And here I thought I was the test mule .

[racingmini_mtl]

It's on its way. The postal service is not always reliable between Canada and the US.

And you'll get to test it also. I don't think it's a bad thing to have 2 persons doing testing.

Jean