Megasquirt Traction Control
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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:
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

Edited by Rod S on 20th Feb, 2010.

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

I was planning on "side on" for the rear hub as it is the only way.

Maybe "side on" on the hardy spicer mounted wheel will be best as well.

I might pop a wheel in the lathe and just check that it works OK that way.

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

Right, I need help with the regulated power supply.

Joes has kindly sent me some voltage regulators, some zeners and some 1 uF capacitors. But I'm struggling to sort out how to connect things up.

I've drawn out the original schematic as provided by Patrick and what I think is the way to do it.


D2 will be the zeners that Joe sent, but I don't know the value. Then I need the values for C1 & C2.

Is the general arrangement of the components correct?

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."

If you have the LM2917 (rather than the 2907) I'm convinced now that it has the zenner regulator internally.

If you scroll down the datasheet for the 29*7 series, they show several different internal connections but fail to actually label the diagrams as to which is which. If a zenner is shown inside the rectangle it means it is internal, just like some of the diagrams show an earth inside the rectangle at pin 8, this is the version for a VR sensor, but again they don't make it clear.

If your version actually has the internal zenner and you feed it from a 9V regulator chip withOUT the external 470 ohm resistor you will fry the internal zenner as the external regulator can supply more current than the zenner inside can sink.

To be certain it has internal regulation, just connect pin 9 to 12V BUT THROUGH a 470 ohm resistor and pin 12 to ground and measure the voltage at pin 9.

If there is an internal zenner, it will read a stable 7.5 volts.

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

Well, page 18 of the datasheet does show the "Active Zener Regulator" fed off Pin 9, so I think that it is safer to use the 470k resistor and zener rather than the voltage regulator.

So the external regulator was a well intention bum steer

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:
So the external regulator was a well intention bum steer

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

No Probs. I'll send the regs onto you then

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:
No Probs. I'll send the regs onto you then

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

Yes, I need to find out what he means by low voltage hall switch. Mine are the usual so I don't expect a problem.

Anyway schematic for a two wheel using the 14 Pin LM2917N:


I did this with a program called TinyCAD. It also generates the parts list and something called a netlist that I can import into another program to design the veroboard.

EDIT: Diodes are the wrong way round in the above picture

Edited by Paul S on 21st 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."

"netlists" are used for designing actual PCBs as well if you want to get really flash !!!

That schematic appears to be just for one front and one rear not four wheels with front/rear maximum and/or average.

Re the hall switches I thought you were using 12V ones whereas 5V ones might be considered more common nowadays.

Patrick doesn't show what voltage he is using to operate them hence my thoughts on the bias resistor.

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

This is my sensor. Probably nominally 12v but can be used from 4.75 - 25v.

http://www.hamlin.com/specsheets/55075%20IssueAF.pdf

It just grounds the sensor wire on activation. That is why the you feed the trigger offset voltage into pin 11.

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."

Pin 11 is for the offset required between the Hall switch supply (12V in your case) and it's operate voltage (0V).

However looking at diagrams TL/H/7942-12 and TL/H/7942-13 in the datasheet they imply a supply voltage (B+ in the diagram I assume means battery) of 12V so I guess Patrick was using 12V switches as well as he has used the pin 11 resistor of 10k shown in the diagrams.

Just found my breadboard but no jumper wires...... I'm going to have to order some of them as well as some ICs......

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

BTW, where did you buy those Hall switches - I might go down that route now rather than risk VR clearances if I fit trigger wheels to the pot joints - and I'm sure you found the best price, so to save me searching........ :)

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

I got the Hall sensor from Digikey.

Part No. 55075-00-02-A-ND

£50 for two up front and then UPS on the doorstep demanding £13 import etc.

EDIT: Got part number wrong.

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."

Interesting,

It's now a 55075-00-02-A but still pricey at £18.79 each.

But from Farnell UK, £46.82 each......

Frightening, I think I might experiment with some of the cheap plastic package ones (~£6 each).

Also, how about this for the pot joint

http://cgi.ebay.co.uk/VW-AUDI-SEAT-SKODA-N...=item51871ff556

Probably too large but pressed on over a sleeve of nylon ???

Only one way to find out, there's another eBay seller with them cheaper but no photo.

May even press over the rear hubs with a suitable sleeve.

Would also give me the higher resolution I'm after.

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

One step at a time Rob.

I've just worked out a layout for veroboard which was difficult enough.

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."

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

Yes, this is still work in progress.

I was thinking that C1 and C2 would actually sit above R3.

I've already spread R1, R2 and D1 plus shifted the ICs down a notch to make things fit a bit better.

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."

Sorry, I shouldn't have said tank - it's just what I was used to at work. a tray is fine with the right chemicals, just slower without the heat.

I've not heard of tracking paper though, need to do some research.....

And £20 for a UV box sounds like a bargain....

The Kicad software is also free and will do up to a full size Eurocard unlike Eagle which will only do half size free. I've not looked at Express PCB and I won't as I've only just got used to Kicad.....

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

Well had a quick play with the a 741 acting as a clamp, it sort of worked bar a strange side effect; despite the 741 being feed by a 5v supply I was able to get the output voltage up to 5.6 volts which confused me. I even dusted off my old copy of "Operational Amplifiers with Linear Integrated Circuits" and promptly realised why I haven't touched it in over 10 years.