Old G-Tech + junk = loggable accelerometer

One old style (red LED, no video) G-Tech
One 9V battery clip
One 1Kohm resistor

Remove plug from cig lighter cable. Open case. Detach
red wire of cig cable from its solder land. Attach red
battery clip lead to this instead. Attach black battery
lead to ground land (white wire, leave it too). Attach
red cig cable wire to a 1K resistor, other end of resistor
solder against Pin 12 of the ADXL105 chip. That's third
pin from the top with the blue capacitors to the right.
You need a fine soldering tip, 50 mil pitch leads.

Now your cig lighter cable has white wire = ground, red
is 0.5V - 4.5V output for -1G - +1G and you still have
the digital readout. Ready for prime time. Tin the ends
and screw 'em down to your MPVI plug.

If you have the old style G-Tech laying around this is
as close to a freebie as you can get. Took me about
10 minutes (not including reading the datasheet for
the part I found inside).

That's freaking sweet!!! I knew the old G-tech would be good for something.

Here are a couple of pics which show the little bit of work needed

Jimmy, does it need the 9V or can it run off vehicle power?

It could be left to run off the cig lighter and just bring out
the single wire to the MPVI but I have this thing about
ground loop errors... though with the relatively large signal
maybe not a real issue. I just prefer to float the thing and
remove all doubt. Same thing with the other box I built,
that one also has two floating instrumentation amps to
use with chassis-referenced sensors like wideband O2
meters.

But anyway, if you want the easiest way, just pigtail
it from the point shown and take your (V-2.50)/2 g.

Interesting project, thanks for sharing.

I have a newer G-tech, so probably won't try this, but lots of venicles are now equiped with onboard accelerometers, I wonder if there is any way to access the signal from the onboard unit so you can log results - in my vehicle the DIC only displays peak acceleration, and only when speed drops below 7kmh. Note to self: Might be time to invest in the service manual and trace some wiring.

:cheers:

It might be worth popping the cover off the newer G-Tech,
it has to have an IC accelerometer in there somewhere that
can be similarly tapped (new one probably has a 2-axis one
but I'm sure the datasheet can be found). Figure the same
with whatever box in your car has the acceleration function.

But I'd rather mung a $40 old GTech than something I'd have
to replace at dealership prices.