[Diy_efi] Traction Control System (update 2)

[Perry Harrington]

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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