[Diy_efi] Traction Control System (update 2)

[Crescent Kao]

First and foremost, I'd like to thank everyone for the amounts of input you
have provided. You've all been a great help and wealth of information thus
far.

Ok, before I dive into more of what you've all suggested, I counted the ABS
teeth on the CV joints. Keep in mind again that the test vehicle is an Acura
Integra using OEM axles. There are 50 teeth on the front and on the rear
joints.

Now.. reiterating your suggestions, the ciruit should now look like this (if
i understand it correctly):


Using the LM339, it has 4 input comparators that will transform the ABS
signal (frequency from each wheel) to a usable square wave. I will then need
4 x LM2907 units to convert each channel from a frequency to a usable
voltage. (the LM2907 has a built in op-amp?) Then I will need an AtoD to
produce a DC signal from which I can then send via the RS232 using an UART?


Do I have this correct? I poked around about PIC programming and found a few
sites pertaining to programming PIC chips. I realize that you must program
in ASM but I did find a site mentioning that you can program using C/C++ and
compile it for use on a PIC (which I would prefer). Anyone have information
on this? Using the PIC route sounds promising, but I'd be lost again as to
how to incorporate this PIC into the hardware.

Thanks!


Crescent Kao
Director of Marketing and Sales
www.c-speedracing.com




-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org]On
Behalf Of Perry Harrington
Sent: Thursday, April 25, 2002 6:58 PM
To: Diy_efi at diy-efi.org
Subject: Re: [Diy_efi] Traction Control System (update 2)


On Thu, Apr 25, 2002 at 07:05:35PM -0700, Crescent Kao wrote:
> Perry,
>   You are correct... Typo on my part.. the signals are actually 70mV at 1
> tire revolution per second.
> I hopped onto NSC website and looked at teh LM339. To be honest - its all
> cryptic to me <grin> I see that it has 4 inputs and thats about all I can
> get out it.

The 339 is a quad comparator.  I turns on at a set voltage.  If you set it
to turn on at ground, it'll turn off when it detects the ABS sensor output.
Meaning the output will be an inverse square wave of the AC signal from the
ABS sensor.

BTW, how many pulses do you get with 1 tire rev?  I have experimented with
VSS sensors and they are about 8 pulses per rev, with 1rev/sec being the
lowpoint cutoff of my existing (non 339) detector circuit.

>
> If I understand it correctly, the LM339 will take an analog AC signal and
> convert it to DC? Even at 70mV would it require a opamp to bump up the
> voltage still?

I wouldn't think so, it's a fairly sensitive piece.  The 339 is operated at
circuit voltage, so you don't need any conversion logic.

>
> Also, what does this Hitachi H8 etc do?

The H8 is a programmable microcontroller.  I'm using one for a project I'm
working on.  It is probably the least expensive development board you'll
find.
It is more than capable of processing the 4 inputs from your ABS sensors.

>
> Thanks.
>
> Crescent Kao
> Director of Marketing and Sales
> www.c-speedracing.com
>

--
Perry Harrington             Linux rules all OSes.               APSoft
()
perry at apsoft dot com 			                 Think Blue. /\

Those who would give up essential liberty to purchase a little temporary
safety
deserve neither liberty or safety. Nor, are they likely to end up with
either.
                             -- Benjamin Franklin


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