TPS Instead of Map & Tacho Output Wiring from Coil Pack

[NickW]

Brent,

First, appolgies for what might seem dumb questions, but.....

I did see a post about this not long ago, but can't find it now...!!

To use a TPS instead of a MAP can I assume that it's as simple as taking the +5v supply that would have been going to the MAP Sensor out to a TPS and the then resultant output from the TPS feeding back to where the output from the MAP would have fed? Possably using a spare connection on the X2 connector (if there is one?)?

The diagram at the bottom of http://picasso.org/mjlj/?q=node/view/2 shows the way to wire up the tacho. I assume that the two -ve connections are the two trigger signals that come from Pins 10 & 12 of the EDIS-4 and go to the two outside pins of the 4 post coil pack?


Thanks,


Nick.

[brentp]

Essentially correct. To use the TPS, you'd need to create a variable voltage signal using the +5v as a reference on the MJLJ. The TPS is a regular variable resistor- 3 terminal device with the center tap being the reference signal.

one terminal gets +5v, the opposite end is GND, and the center is the voltage reference. this voltage reference is what is fed into the line going into the processor.

You need to ensure that you get the pins correct. I'd suggest looking at the megasquirt instructions on setting up TPS http://www.megasquirt.info . Also know that I haven't tried this yet- so when you get it working, perhaps you can do a write-up on it!

As for the coil pack, you have it correct. the outside two pins on the coil pack are fed into the tach adapter circuit.

Good luck,
Brent