[Diy_efi] Traction Control System (update 2)

Bevan Weiss kaizen__ at hotmail.com
Sat Apr 27 21:22:14 GMT 2002


I'd recommend that you only program PIC's in assembly (unless dealing with
the like of the 18c/fxxx's).  There are only like 35 instructions, and only
one working register/accumulator to remember.  The assembly coding is pretty
simple, and normally the actions that are required of them are best
described by the assembly instructions anyway.

As for the conversion, you'll have the toothed wheels->frequency-voltage
converter-> PIC's ADC -> PIC's UART/I2C/whatever -> host computers
UART/I2c/whatever -> processing.

I don't think that the PIC would have enough processing power to do the
necessary math on the obtained results.  And doesn't(shouldn't) really have
enough influence in any other decisions to be of influence with things like
changing timing(or spark presence), or fuel.  Instead it would supply the
host (possibly another control chip running on the same bus as the EFI332)
with enough information(absolute wheel speeds) to make a valid decision, and
can then action that decision.

----- Original Message -----
From: "Crescent Kao" <crescent at c-speedracing.com>
To: <Diy_efi at diy-efi.org>
Sent: Sunday, April 28, 2002 9:10 AM
Subject: RE: [Diy_efi] Traction Control System (update 2)


> 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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