TPS sensor (was MAP Questions...)

[Donald Whisnant]

>
>Jim Staff writes:
>
>>      I don't know how to make a Throttle Position Sensor, But I'm sure 
>> somebody here know or I could find it out god knows I've found out 
>> impossible stuff already.
>
>Jim, head down to your local auto parts store and ask the guys behind the 
>counter to have a look at a Standard Motor Products or Echlin emission
>controls catalog.  These have nice little pictures of a zillion different
>types of throttle position sensors, I'm sure you could find one to fit 
>your application.  It's just a pot, hook the ends to 5V and ground and
>read the voltage at the wiper to get throttle position.  Resist the 
>temptation to just use a 99 cent pot from your local Radio Shack, they
>are not made for the constant dithering and movement that a TPS sees.
>Once you get this data, you're on your own...

If you want to make a good TPS, you can get a high quality, wire wound 10
turn pot (like a Beckman or Bourns).  This will require a little machine
work (so having a machine shop or specialty parts is a must)...  Make either
a gear drive assembly or better yet, use a couple of timing belts and
timing pulleys.  This is required to convert the approx. 3/4" movement into
a 10 turn movement.  This will provide much better resolution and a MUCH
better output signal.  A 100K pot or something close would be good.

Now, that is a "good TPS" but if you want and absolutely "fabulous TPS", and
one that is even mil spec, you will need a Resolver and a Converter circuit.
A resolver is a rotatary device that outputs a sine and cosine of the angle
at which it is position.  The military uses them in missile guidance systems.
... The great thing with a resolver is that it is basically frictionless PLUS
it is VERY VERY accurate.  AND, it is extremely water resistant (unlike your
off the shelf pots) ...  HOWEVER, they are expensive (about $300) and require
a driver/converter circuit -- also another expensive piece...   BUT, this
would be the ULTIMATE in TPS sensors...

Maybe someday, if I have some money to waste on a resolver, I'll give it a
shot...

Donald Whisnant
dewhisna at ix.netcom.com