Hi,
I'm building a sleeper MGB with a 3.5l V6 - trying to keep external appearance stock. So, I want to use the original in-dash Tach, but don't really like the recommended circuit for generating high-voltage signals to the old-school tach pick-up.
I've seen that MS2/extra can be directed to put out a variable-frequency 5V square wave depending on RPM. I'm thinking to route that signal to an Arduino mounted inside the old tach housing, and use it to output a 0-1.5V PWM signal to drive the tach needle directly. I'm wondering:
a) has anybody successfully tried this before? Any advice?
b) to do this, I'd be sending an un-protected signal direct from the CPU to the world outside the MS box. Arduino runs 5V, so I'm not too worried about accidentally pushing a voltage back to the CPU. But, you never know what inductive currents might be floating around behind the dash... Does this seem like a bad idea?
c) what's the current capacity of the 5V supply on MS? I'm already running a TPS, crank position sensor, external MAP, and fuel pressure gauge from this supply. Arduino doesn't use much current, but I wonder if I'm pushing the limits?
Thanks for your thoughts!
Tach output & Arduino
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