Re: [Amc-list] WANTED: Spirit/AMX/Concord/Eagle Dash Cluster forcomparison to GW cluster

[Tom Jennings <tomj@xxxxxxx>]

Sandwich Maker wrote:

> this means it's an indirect measurement of rpm and would read falsely
> on anything other than a stock coil.

Yeah, but it would probably be proportional, if that's any consolation. 
Eg. 8% off across the scale, or whatever.

I have one of these in my 70 Hornet. I have it kludged up in a way I 
don't recommend! But the "right" way to convert a current-based tach to 
a voltage-based one is to use an electronic switch and a series resistor 
to simulate the coil. My favorite switch chip is the VN920 (ST 
Electronics), $5, give it a tiny signal it'll power any inductive load 
with no damage and no extra diodes or spike-clamping parts. One will 
drive a car horn or headlamp! It's short proof, will handle 42V and 30 amps.

Haven't done that but I did run a million cycles with a fuel injector as 
a test for a robotics project. Worked perfectly.
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