Digital automotive tach circuit?
in [Basics]
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From: default on 30 Oct 2006 08:17 On Sun, 29 Oct 2006 22:03:50 -0500, "Tam/WB2TT" <t-tammaru(a)c0mca$t.net> wrote: > >"Noozer" <dont.spam(a)me.here> wrote in message >news:GmQ0h.206269$5R2.25840(a)pd7urf3no... >> Anyone have a simple digital tachometer schematic handy? >> >> I want to put a 4 digit LED tach into my van. Resolution of 50rpm is fine. >> Fed by the TACH output of a six cylinder GMC on distributor coil. >> >> If it isn't much more difficult, I'd like to be able to drive a bar graph >> of 12 to 16 LEDs as well. >> >Build a frequency counter, and pick the right gate time. I think if you make >the gate time 1/300 of a minute, the display will show RPM/100. Make it >1/30th of a minute (2seconds), and it will display RPM/10. There is a common >coil? > >Tam > That's too obvious. I'd stuff a down counter with a preloaded number corresponding to some very high RPM then use the tach signal to gate a series of pulses from a crystal oscillator into the counter. Sort of measuring period, but displaying RPM . . . Requires some latching/gating to display the count while the next count is being acquired. Main advantages: capable of very high resolution and fast response, with low pulses per revolution. The concept works; I had it bread boarded and up. An analog display was more intuitive and I could acquire the RPM in a millisecond glance, so used analog instead. Digital displays make more sense in slow flying aircraft IMHO. ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |