[Diy_efi] Traction Control System (update 2)

[Crescent Kao]

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.

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?

Also, what does this Hitachi H8 etc do?

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 5:44 PM
To: Diy_efi at diy-efi.org
Subject: Re: [Diy_efi] Traction Control System (update 2)


First, your .7mv reading seems WAY too low to me.  I'd expect about
300-400mv.
At full tilt, over 1v.

Second, you are going at this with much more complication than neccessary.

Go get the NSC datasheet on the LM339.  Look through the applications
section
and find the app for a single supply Zero Crossing detector.

Implement that circuit 4 times for an LM339.  Hook it to your ABS sensors.

You now have 4 digital pulses which mirror the ABS sensors.  Now you can use
the PC parallel port directly for capture.

I would recommend a standalone controller, something like a Hitachi H8/3664
evaluation board ($50 from Avnet, $99 with cables and power supply).

--Perry

On Thu, Apr 25, 2002 at 05:16:29PM -0700, Crescent Kao wrote:
> Ok.. we've made a little more progress on the traction control system.
> Here's a recap of what we have so far:
>
> . Test vehicle - Acura Integra with ABS
> . Signals generated from the ABS sensors - 0.7mV AC (and up, depending on
> speed)
> . Probing the ABS wires at the ABS brain verified the signals. The AC
> voltage increases as speed increases. (around 1.4mV at 35mph
>
> So... at this point we were looking into how to convert the signal to a
> digital signal and read it via a serial connection (RS232) to an onboard
> laptop.
>
> This is what we have so far hardware wise:
>
> . using an op-amp, bump up the 0.7mV+ input signal (above 1v?)
> . then convert the AC signal to DC
> . convert the analog signal using an AtoD processor
> 	(perhaps NSC ADC08034 http://www.national.com/pf/AD/ADC08034.html 4
> inputs -
> 	  however it specifies that it interfaces using "Microwire". I have no
idea
> what this is. Should we use an 		  AtoD that uses parallel interface
> instead?)
> . format the signal to a usual datastream
> . send the data via UART (9600 or 11500 baud) to the RS232 port
>
> This is our current challenge. Does this approach sound correct?
>
> Crescent Kao
> Director of Marketing and Sales
> www.c-speedracing.com
>
>
>
>
> _______________________________________________
> Diy_efi mailing list
> Diy_efi at diy-efi.org
> http://www.diy-efi.org/mailman/listinfo/diy_efi

--
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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