[Vwdiesel] Different GP monitoring cct stuff

[Val Christian]

Yes, I confess to using sampled Hall Effect devices.  The thresholding
was fairly stable, and all I did was drive a low frequency LED output.
If it flashed at about 4 per second, I drew 40 amps.  3 per second,
it was about 30 amps, etc.  The flash rate is easy for a regular  car
operator to sense, and it only flashed when the GP had power from
the relay.  The HE device, the NE555, and the LED were tie-wrapped 
to the relay output.  Power was derived from pins into the relay socket.
The LED faced downward, and could be seen by day with a mirror, and 
by night reflecting off my pant legs.  

I was not worried about identification of which GP was failed, as
that can be done under the hood with numerous techniques.

I looked and don't have the circuit.  I was something I just did up
as a poor man's breadboard, and then decided to use, more as an 
experiment, than as an intended diagnostic tool.

Frankly, on most of my cars, if I want to verify GP operation, I just
turn on the dome light, while cycling the GPs.  I usually don't
have the best batteries, and the dome light dims a perceptable 
level for normal operations, when temperature adjusted, blah, blah.

I fall back on my earlier recommendation.  Put in a loadmeter and a 
charger meter on your diesel.  That way you can monitor many different 
things on the car, including fan current draw, headlight current draw,
rear window defogger current draw, AC compressor and system draw,
and so on.

Sorry to start so much debate.  The fuse is a pain when it fails, and
fatigue is a factor.  There are lots of ways to verify GP operation.
BTW, for over a year, I have carried a passive IR radiometer to measure
temperatures.  You can even detect underinflated tires, by measurement 
of their temp immediately after stopping.  And it's nice to know that
the squeak you thought you heard from the right read drum is accompanied
by a drum temp of 160F after a long drive.  Lots of uses.  And the 
laser pointer on it can be used to blind any oncoming terrorist drivers,
should that be necessary.  Right.

Val





> 
> Hi Dieselheads ! Clatter clatter clatter (marbles in a glass bowl)
> 
> Well, I finally got my 5 Allegro Hall-Effect current sensors (ACS750xCA-050)
> in the mail here today and tried them out. (free samples btw !)
> Output voltage swing is very slight.  For 2.5A of current (I used a 12v/100w
> light bulb) @ ~12VDC, the output is about 3.2V....
> Even w/o any current being drawn (lightbulb off)  the output is about 2.5V
> According to the spec sheet, even at 10A (what a GP might draw) I am
> probably only looking at a very slight increase....aprox 3.5V I think.
> (they also require a Vcc of 5Vdc....I can use 16Vdc max, but the outputs are
> very squirrely to say the least, even @ 12Vdc)
> 
> If I were to put one inline with each GP, I'd still be down into the mV
> range of variance w/o using some kind of op-amp cct to boost the overall
> output swing.
> 
> I suppose we could say, if I read *anything* over the resting output voltage
> of 2.5V, then we have current flow, thus the GP *is* working.
> 
> They are rated @ 50A each, so I could stick just one in the main line, just
> after the fuse and would see a 2.5V-4.0V (40A) swing if all plugs were
> working, however the voltage swing is so slight you probably wouldn't notice
> if only 3GP's were working.  Of course, this theory is all out the window on
> the second attempt to crank,  when your battery is weak, or you're cranking,
> the dome light is on....anything to change the Vcc from its
> nominal(original) 12Vdc before you touch the key !
> 
> Hmmmmmmmm...maybe I'll just go back to the big honkin' blocking diodes and
> LED's (Mark the Miser)....or a cheapie $10 multimeter and a 4P switch like
> Hagar... Was it Val who used Hall-Effect sensors in the past? (I forget)
> 
> 11 pages- Data Sheet http://www.allegromicro.com/datafile/0750-050.pdf 
> Main page http://www.allegromicro.com/sf/0750/
> 
> Mike in NB, Canada
> 
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