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.: corvette tachometer |
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In the 1970's the
Corvette started using an electronic
tachometer. I wanted to keep the
original tach., so I had to figure out
what signal it was receiving from the
distributor. |
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This is the back of the tach. - only
three connectors: power (p for pink),
ground (bk for black), and brown from
the distributor.
I
couldn't find the specifications for the
signal going into the tach., so I
guessed it was a pulse of some shape? |
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This is a old Heathkit power
supply I bought in the early '70's that
I use for supplying simple signals. It
has a square pulse output, but only goes
down to 200Hz.
Doing some quick math, 200Hz is
equivalent to 12,000 rpm! But, an
8-cylinder engine has 4 ignition pulses
per revolution. So, 12,000 rpm divided
by 4 = 3000 rpm. |
If my guessing is
correct, if I put a 200Hz square pulse
at the tach input, I should get
3000 RPM on the tachometer. To be safe I
set the voltage low (3 volts).
And,... it worked.
Okay,
not an exciting ending (and no
picture), but it's better than smoke and
fire.
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There
is more to come as I need to make a
triggering device that mimics an
8-cylinder engine - 4 pulses per
revolution.
I
already have the parts, and have tested
it, I just need to build it and mount it
to the motor. |
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