Autometer Tach requirement

[psyolent]

Hi - not sure if this is the right place, so here goes, definately a question for the more cleverer electronics people than me.

I have a need for an Autometer tach on a V6.
Autometer sell a unit which converts the signal for 'CDI' systems, which, costs as much as the flaming tach.

Now ; if I remember from the Saloon car days, the V6 output is positive which is different to the coil negative output that the tach expects.
Is there a switching transistor (ie: a very fast fucking relay) which could do this work, obviously with filtered supply and heatsunk? Or could you use an OpAmp (prolly not as they usually get fed AC.

[Charlescrown]

I used a TIP122 transistor to switch the polarity of a fuel pump relay. It's been working now for 2 years so reliability is not an issue. Switching speed might be another issue.

[delcowizzid]

if it wont drive off the stock tach output you can run all 3 coil negatives out from under the coils through a diode each to stop them all triggering at once aand join them together to feed tach

[Holden202T]

my brother fitted an autometer tacho to his V6 and he hasn't had any issues with it working from the stock wire ?

[psyolent]

holden202t - did he buy a specific autometer model of tach?

delcowizzid - good idea.

toyotacrown - i'll look that thing up and see if it would work.

[Holden202T]

wouldn't have thought it would matter ? but im not sure what it is, i'd say from memory sports comp or something like that....

edit: its this one
[youtube]http://www.youtube.com/watch?v=BlYCiP4lN8s[/youtube]

[psyolent]

my eyes aren't that good.

[Holden202T]

sorry thats all i can offer at the moment

[antus]

I'd say try it first. I think theres a good chance of anything made in the last 10 to 15 years just working fine on the tach output. If not theres a few threads about using a relay coil (remove the bar) to do it. It might be in the faq. If its not let me know and i'll add it.

Edit: its there - see the Q "Will a traditional coil signal reading tacho work with a coilpack? Can I make it work?"

[psyolent]

thanks mate. will have a gander. good man.