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From: vbreault@rinhp825.gmr.com (Val Breault)
Newsgroups: sci.electronics
Subject: Re: Inductive pickups.
Keywords: Inductive Pickup.
Message-ID: <54642@rphroy.UUCP>
Date: 30 May 91 15:27:15 GMT
References: <1970@ole.UUCP>
Sender: news@rphroy.UUCP
Reply-To: vbreault@gmr.com
Organization: General Motors Research Lab. Warren, MI
Lines: 47
Nntp-Posting-Host: rinhp825.gmr.com

In article <1970@ole.UUCP>, ssave@ole.UUCP (Shailendra Save) writes:
> 
>   I am trying to get a signal from the drive shaft of my car
> using an inductive pickup. (To calculate and display speed)
> Before I get under and get dirty, I wanted to know if anyone
> has had any experience with a similar transducer? Can you 
> recommend one? The car being a big hunk of metal, and the 
> tolerances between the "magnet" and the pickup being of the
> order of 0.2 in., will it work? 
> 
>   Any related ideas?  

There's a lot of stuff happening under your car.  Stones, water, vibration,
dust. Then too, the driveshaft will wobble several thousandths on it's spline.
Rather than attempt to make something that will work in that rather hostile
environment, why not try this idea?
 
In the days before automotive computerization, a cruise control setup 
consisted of a mechanical device that was attached via flexible cable
between the transmission and speedometer.  You should be able to get one
of these pretty cheap at a nearby junk yard (oops, 'Automotive Recycler').
It will contain all the necessary parts (bearings, etc.) to make the
mechanical part of the project pretty easy, as well as getting it up into
the engine compartment, away from the dust, water, stones and vibration 
that a tailshaft installation would be subject to.  It would also allow
you to continue to operate your analog speedometer and odometer while
developing the digital ones.  

Another thought would be to get the transmission mounted component for
a similar car that has an electronic speedometer.  I'm going out on a 
limb here, but I believe they mount in the same place on the tailshaft,
and output a number of pulses per driveshaft revolution.  This solution
(if at all 'do-able') would get you out of the mechanical construction 
part of the project entirely.  It won't however allow you to run the 
existing speedometer and odometer in parallel.
 
> 
>   Shailendra
>   ssave@caen.engin.umich.edu
>   sumax!ole.uucp!ssave

-------------------------------------------

Val Breault - vbreault@gmr.com

The opinions expressed by the author do not necessarily reflect the position of the General Motors Research Laboratories or the General Motors Corporation.