Megasquirt Traction Control
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dug these out of the bin of wonders...are they viable ?

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

If I've read the number right from the photo (285-829) they are discontinued and are proximity switches rather than hall effect, their current replacement (249-2237) has a maximum frequency of only 800 Hz.

So I would say ...No..

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

Edited by Rod S on 20th Feb, 2010.

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

thanks rod ,worth a try !

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

Actually, looking back at Paul's calculations he gets 430Hz with a 12 tooth wheel so it's within their range if they are the same specification as the replacement items that RS lists.

It's only me who is thinking of much higher frequencies.

So might be worth a try - I have to admit I don't know what the difference is between a proximity switch (which is what RS describe them as) and a Hall switch, and the datasheet on RS doesn't help....

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

Just ordered my parts from Farnell.

Enough to do a 4 channel system with maximum from the rear and maximum or average from the front.

I've gone about it in a different way, I'm hoping to be able to fit the ABS trigger wheels I mentioned earlier to both the pot joints and inside the rear hubs, they are 42 teeth so will have a much higher resolution at low speeds anyway and found some miniature Hall switches which are optimised for the finer teeth on an ABS wheel. They are not in a nice neat package but just a plain chip designed for the automotive industry to install in their own packages so I'll have to improvise with some epoxy but a lot cheaper and a lot smaller than Paul's choice.

With the higher resolution wheels I may not limit the voltage range to low speeds only but I've still ordered some OpAmps to use as voltage protection on the CPU and give me the option of high or low speed, might even make it switchable....

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

I've just tested my Hall switches against the trigger wheel in the lathe. They are not as gap tolerant as I would like.

I tested it axially and radially. I used the LED setup from the cam sensor test.

Once the gap goes above 2mm, you start to lose stability.

At the optimum gap setting of 1.5mm, there is about 4mm tolerance from side to side.

So radially on the wheel, you could move the sensor 4mm each way from the centre point on a 4mm thick wheel. This dropped to 3mm each way at the 2mm gap. By 2.5mm gap you could see the instability.

Axially, on the 12 tooth wheel with the large teeth, I had 8mm of sideways movement of the sensor at 1mm gap, dropping to 7mm at 1.5mm gap and just 2mm at the 2mm gap. The optimum setting is with the sensor centreline 3mm in from the outer wheel edge.

I also check out pot joint movement on a couple of gearboxes. On a recently rebuild box with about 2000 miles, there was negligable movement. But on an old box with 80,000 miles it was all over the place.

I'm going to mount the driveshaft sensor axially for ease of mounting as there does not seem any advantage in mounting it radially.

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."

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 ???

I've drawn up a 3 wheel system as attached. As it would be very easy to extend in the future, I may stay with the 2 wheel for now.

Attachments:

15.76kb

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."

Your diodes from pin 11 to ground are the wrong way around !!!!

Plus you've used the symbol for a zenner but that would just be me being picky :) :) :)

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

Thanks Rod. I did say that I do not know what I'm doing

I've updated the drawing above.

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."

Looks fine now, even the right symbol

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

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 , on the tvr im using a sensor mounted on the hub and a series of magnets on double sided tape on the inside of the wheel rim,this has worked for the speedo for ages ,might work ?
you could just use pieces of metal instead of magnets ,youd just need 12 instead of my 4 ?

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

If it's good enough for Heath Robinson, then it's good enough for me

I'll stick with the trigger wheels and hall sensors now that I have paid for 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."

Well my bits arrived today,


The sensors (Hall switches) are really small so should be no problem to mount and encapsulate them in a bit of epoxy.

The gamble on the ABS rings was slightly less successful - I had assumed that anything VW/Audi/Seat/Skoda would have bigger hubs and/or drive joints than a Mini pot joint and that I would need to machine up a nylon sleeve to enlarge the joints to press these on. In fact they are about 2mm smaller than my pot joints (and I'm not sure if mine are the "large" or the "small") so I'll have to machine a little bit off.
On one hand that will be a real pain as others have already said how hard they are but has the advantage that the overall diameter won't go up by much - the downpipe from the turbo is very close to the right hand one so the smaller the package is, the better.

Just need to assemble all the elctronics on the breadboard and check I can voltage limit the outputs the way I intend.

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

excellent most my parts are on the way too :)

Edited by Brett on 23rd Feb, 2010.

Yes i moved to the darkside

Instagram @jdm_brett

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

hello
I've been reading this thread with the up most interest, as i do like to dabble with electronics from time to time,

However i must say so far this seems a little above my capabilities but i am learning and i'm very impressed at how quickly this is all progressing and i will definitely be keeping a close eye on this thread

I hope it all works as expected

Luke

Well I did a quick test of machining the Pot joint for the ABS ring and much to my surprise, I can actually machine it in my cheap Clarke lathe



Also, perhaps not so much to my surprise, Leyland/Rover couldn't machine it right in the first place....

I saw, even with a rotating center in the arse end of it, that the OD was slightly eccentric....

Clocked it and 5 thou out... Sorry, old units, my DTI is antique.. about 0.12mm

So I need to find out if it's the internal splines that are out or the outside before I machine any more........

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

Yes i moved to the darkside

Instagram @jdm_brett

rod isnt there a chance that the pot will move up and down a bit and throw the signal off ,is it a lets see what happens thing ?

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

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

cool , i suppose making sure the bearing that locates the pot is tight would help .

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