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
============================================ try epanorama. This would also be a good project to learn c programming on a microcontroller. Use a text lcd as the bar graph. Or a graphics lcd. Look at the Olimex MT128 at olimex.com
How about doing it the old-fashioned analog way ? An LM2907/2917 as F-V converter, and a 4 1/2-digit DVM module for readout. Another venerable IC, the LM3914 could provide the bar graph display, two of them for a 20-dot scale.
A Digital Tachometer For Your Car
Compact design features a 4-digit LED display and a bargraph. It can also provide gearchange indication and drive a rev limiter.
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.
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