Car Digital Tach Display

[GoingFastTurningLeft]

I'm looking for some pointers into this...

I want to build a digital tach for my car. I'm not looking to do anything microcontroller based (at least at this point in time). From what I understand, it either emits a pulse every revolution or twice a revolution, which i've been able to condition this down to regular logic levels. I plan on doing this with 4000 series ICs.

I'm figuring i'm going to be very limited in how many digits I can display since the pulse train is so slow. 2 is ok with me. My only demand is that it has a very good refresh rate.

I was thinking of using 4017's, as well as some 7-segment LED converters. Probably need some sort of latch in there as well. I figure I need to have some sort of internal timer to set the refresh/reset rate.

Any pointers?

[Robert Reed]

Check out the May 2006 Nuts & Volts. Has a construction project about a digital tach, It is a four digit display with the last two digits being dummy zeros so it can only resolve in 100RPM increments, but is has a fast response time.

[RDL2004]

You might check out this project for ideas

http://members.shaw.ca/roma/fc.html


- Rick