Any way to use a tach signal like this?

For discussing how to choose sensors and create a wiring harness for all Bowling and Grippo versions of the MegaSquirt® EFI controller.
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TheSteve
MegaSquirt Newbie
Posts: 5
Joined: Sat Dec 15, 2007 1:53 pm

Any way to use a tach signal like this?

Post by TheSteve »

I'm trying to use the Tach signal wire on my 97 GSXR to control a fuel only MS. The weird thing is the ignitor box shows 12v on the tach wire at 0rpm and seems to bring it low to pulse the tach. The thing is, it never seems to drop all the way to 0v and the MS won't pick it up. While cranking the voltmeter shows about 2.5 to 4 volts. Is there any way to get this to work?

Triggering from the coils is a no go, the primary side of the coils run at 200v. Unless theres something I havent heard of that allows this to work.

MS1 3.0 stock code
Matt Cramer
Super Squirter
Posts: 2951
Joined: Sat Jul 03, 2004 11:35 am

Re: Any way to use a tach signal like this?

Post by Matt Cramer »

Weird signal, but I've seen them before. You could build an op amp comparator circuit that sends out 12 volts whenever the signal drops below 6 volts or so. Or take a 5 volt zener diode and put it inline with the tach signal, banded end away from the MS.
TheSteve
MegaSquirt Newbie
Posts: 5
Joined: Sat Dec 15, 2007 1:53 pm

Re: Any way to use a tach signal like this?

Post by TheSteve »

The zener diode trick sounds promising. Ill give it a try tonight or tomorrow.

Thanks
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