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G3X RPM input

crabandy

Well Known Member
I'm definitely not an electronics guru, soooooo this is just me trying to understand how to hook all of this stuff up.
My EFII electronic ignition sends a short pulse tach signal that goes from 0 volts to 12 volts and back. The standard 4 cylinder tach signal is two pulses per engine revolution.
Will this signal work with the G3X tach input? Will I need to add a resistor to reduce the voltage?
Thanks,
Andy
 
Hi Andy,

A 0-12V signal will be just fine. I would guess that your EFII outputs two pulses per revolution like most wasted-spark ignition systems. However, in order to support a wider variety of electronic ignitions, we have recently changed the G3X EIS configuration interface to support tach signals with 1, 2, 3, or 4 pulses per revolution. So if your ignition outputs any of the above, you should be covered!

- Matt
 
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Wiring J243 on GEA 24

Does the single tach wire supplied by the efii ignition go into pin 8 and pins 7 & 9 are not used?
 
I just configured my RPM2 port as EI 2 pulses for my SDS CPI ignition. RPM1 remains configured for the Hall sensor on the right mag. When I checked the display, the RPM gauge appears the same as before. Should there be another RPM gauge, or a split pointer / two value boxes? Does it average the two inputs? Have I omitted a config step? Note the engine was not running - I haven't had my first start yet / timed the EI.
 
It will use the higher input

I believe this note in the G3X installation manual would apply to your situation.
"Aircraft with dual electronic ignition systems can connect the tachometer signal output from the second ignition to the GEA 24/GSU 73 RPM2 input (see Figure 30-2). The value displayed on the RPM gauge will be the higher of the two RPM signals."
 
RPM Sensing Circuit

Hi there,

I?d like to build my own Hall effect RPM sensor for my Slick magneto. I have a few carcasses of Westach and JPI sensors that I?ve hollowed out and it wouldn?t be that hard to pot in a $1.50 Hall effect IC to fix them.

My question is, what is the GEA24 expecting from the rpm sensor? Most Hall effect ICs call for a pull-up resistor between Vdd and GND and a pull-up resistor between VOUT and Vdd. Do I need to include these in my circuit? Or, are the capacitor and pull-up resistor internal to the GEA24 allowing me to connect the 3 pin hall sensor directly to GEA24 J243 pins 7-9 (or 5,6,10)

Fitting the capacitor and resistor into the magneto rpm sensor would be a challenge using through-hole components.

I plan to use a unipolar switching sensor that would output Vdd (12V) in one pole?s field and a few mV in the opposite field.

Thanks for the help,
Joe Czabaranek
 
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