Megasquirt Traction Control
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Schrödinger's cat - so which one am I ???

Edited by Rob H on 18th Feb, 2010.

Schrödinger's cat - so which one am I ???

yes you need caps on the input and output Paul,

let me know your address and i'll sort you out some 9vregs and caps

probably got some zenners and things too if you need them.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Yes i moved to the darkside

Instagram @jdm_brett

Brett, the only potential issue is that you need the same numbers of teeth front and rear.

This is my collection of parts coming together:



A bit of machining to do and then tack weld the wheels on.

Edited by Paul S on 19th Feb, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Paul have you checked the clearance between the trigger wheel and the rear wheel cylinder ? I had a problem with this when fitting a sensor for a rally tripmeter.

Mine only just clipped the dust cover but it was enough to cause problems.

"So wat we gonna do tonight Brain?"
"Same thing we do evernight Pinky!"
"Try to take over the world!"

I will check it. There is scope to machine the OD a little, but not a lot.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I'm still thinking about this....

(something I often do instead of progressing forwards)

1 - I'm definately going to use Op Amps as voltage clamps (as Robert suggested) to allow better resolution at low speeds and ignore high speeds. I'll probably add some 4.9V zeners to protect the CPU if everything were to go pear shaped....

2 - Might use VR instead of Hall, the circuitry is simpler and can use the 8 pin package as the trigger offset isn't required with VR.

3 - Will definately look at using a sensor inside the gearbox for the front as per Brett - altering the R and C values for different teeth is straightforward, a pot for "R" would allow fine tuning.

4 - Don't like the 12 tooth wheels, I would prefer more teeth for better resolution al low speeds. Most OEM traction control systems seem to use the ABS signal which is derived from many more than 12 teeth..... but I can't find anything better than 12 yet that could be fitted to our antiquated design.....

Just rambling at the moment....

Schrödinger's cat - so which one am I ???

Rod,

Using a Zener on an ADC input is not a good idea. The Zener will start conducting way before it's rated voltage and will skew the results: anything above about 4V (maybe less) will be unreliable.

Jean

Edited by jbelanger on 19th Feb, 2010.

http://www.jbperf.com/

It's stupid question time again but do you really want to be measuring one front wheel and one back wheel? or would you be better measuring the two front wheels? as I would have thought the differential would lead to one of the driven wheels to start slipping before the other one, even with a LSD or ATB.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Schrödinger's cat - so which one am I ???

If the Op Amp is rated for it, it should be ok. Remember that you want a rail-to-rail OpAmp since you want the output to cover the whole range.

Jean

http://www.jbperf.com/

Rod,

Just think about the scenario of getting to, say, 70 mph on a wet road and full chat and the traction control turns off because you've reached the 5v frequency.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Rob (1) I was assuming measure all four wheels. The LM29*7 datasheet shows how to wire them for maximum, ie, if you measure both the rears it will ignore a lifted inside wheel. For the front(s) it would seem more logic to measure the average which again can be done electronically with a pair of sensors or mechanically if measuring at the diff/gearbox.

Paul,
1 - High speed, possibly more dangerous but I'm not aiming for massive power so would prefer to optimise it for leaving the traffic lights (or the pretty coloured lights on the drag strip for the rest of you !!!)
2 - VR may be more noisy for precise timing events but the LM29*7 uses very basic principles for its frequency to voltage conversion so I would think not much of an issue. All the ABS sensors I've unplugged are only two wire from memory so are most likely VR.
3 - Running off the crownwheel/gearbox, as Rob (1), gives the average, also with pot joints (my case) its hard to see how to mount a trigger wheel. Also, I've never seen an output shaft without play even with brand new bushes in the cover plates so keeping a uniform gap could be an issue, less so with hall as they have quite a distance range as you have proven, but VR would be a problem as it likes a nice small gap.
4 - 12 teeth is probably a good compromise for all speeds but mathematically poor at low speeds. Again, I was thinking of how to optimise it for the traffic lights.

Jean, I have no practical experience of using an Op Amp as a clamp, although the theory is sound, but I'll mock it up first and see.

Rob (2) - Yes, I had thought of that hence my referring to it as LM29*7, ie using the 2907 without the internal regulator. Just need to see what the losses in the output stage are.

Just need to find my old breadboard and reconfigure my little USB scope as a function generator to see how this works. The electronic components are cheap, it's the hardware (trigger wheels, sensors) that are pricey.

Schrödinger's cat - so which one am I ???

nonsense post deleted.

Edited by robert on 20th Feb, 2010.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Edited by Rob H on 20th Feb, 2010.

I saw what you wrote, leave Mr Stick out of this!

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Schrödinger's cat - so which one am I ???

Rod, if you buy the latest minimag, you will se a picture of a toothed wheel on a pot joint and what is most likley a VR sensor.

Plus what looks like a load of swarf sticking to it

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by Paul S on 20th Feb, 2010.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

On 20th Feb, 2010 Paul S said:


Plus what looks like a load of swarf sticking to it

Yes i moved to the darkside

Instagram @jdm_brett