Pulse width output on Tach Output

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boxertwin
MegaSquirt Newbie
Posts: 14
Joined: Fri Apr 06, 2012 4:48 am

Pulse width output on Tach Output

Post by boxertwin »

Funny one this, and it is probably my own doing, But I cant get my Microsquirt V2 to drive my nice carefully hand made one off 50 year old replica VDO tacho!!

I have checked and the Squirt Tach Output is producing a healthy 12V output signal - but the pulsewidth is only 150 microseconds long. This is fine if you are playing with nice new revcounters which are intended for digital drive, but older ones will not work with a pulse input much less than 2 ms, since they have much slower noise suppression inputs. - and YES my nice hand crafted replica rev counter works perfectly with a 2ms input pulse!

I am running Squirt V2s with V2.8800, and V2.88600.

I am sure that someone will say - buy a nice new V3, but then the V2s work rather nicely (apart from not having a compatible tach output signal) - and they have built in coil drivers!

Options?
1) change the Tach output pulse width - how? (V3 software?)
2) drive the B***** thing from the coils!
3) make up a simple pulse expander using a PNP and NPN transistor!

sane suggestions greatly appreciated!
grippo
MegaSquirt Guru
Posts: 921
Joined: Mon Feb 16, 2004 6:55 pm

Re: Pulse width output on Tach Output

Post by grippo »

You could try running 3.780 code - it allows you to specify the pw and duty cycle of the tach output.
boxertwin
MegaSquirt Newbie
Posts: 14
Joined: Fri Apr 06, 2012 4:48 am

Re: Pulse width output on Tach Output

Post by boxertwin »

Many Thanks,

Can I run this on early V2 Microsquirts?

John.
grippo
MegaSquirt Guru
Posts: 921
Joined: Mon Feb 16, 2004 6:55 pm

Re: Pulse width output on Tach Output

Post by grippo »

Yes, but read the V3 documentation for all the code and input changes.
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