For discussion of Speeduino compatible boards designed / built by other members of the forum and for guidance around making such a board
By Richard Bell
#56496
one for the circuit guru's

I'm making an MR2 PNP board so to work out the issue with the 4wire dizzy with the max VR being used i sketched out the 3 pickup circuits the OEM board uses, any issues replacing the 1N4782 (8.5v 1.0mA) with a same/higher mA 4.7v zener so i can stick the signal into the arduino through another 470r/1k resistor after the diode and last cap?

setting the dizzy up tomorrow on the bench and scoping the signals to see how this all works but i figured someone's looked into this to make the honda/toyota specific VR conditioner.

the passthrough caps are all 2.2nF 100v just forgot to lable them.


Regards
Richard
Attachments
Toyota mr2 3S-G circuit.PNG
Toyota mr2 3S-G circuit.PNG (41.5 KiB) Viewed 5373 times
By Wombat
#62109
Whenever I have worked with Honda dizzys, I have always used either the 24 and single toothed wheel in combination (sequential ignition), the 24 tooth wheel with 2 teeth grounded off to simulate a 12-1 wheel on wasted spark (megasquirt 1-extra was incapable of decoding a single missing tooth wheel at cam speed) or the 4 tooth wheel by itself when using the distributor.
Suggest using just two or one of the three (if your Toyota has three like the Honda does).
I personally hate VR sensors as they are noisy and cause all sorts of problems and require expensive chips to decode the messy signal they produce.
I used to use the NCV1124 (now out of production) but I eventually converted a Honda dizzy to work with a magnetic hall sensor so it outputs a good solid 5V signal whilst still using the Honda toothed wheel.

Good luck with your circuit

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