Digital automotive tach circuit?
 

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.

Digital automotive tach circuit?
 

Noozer wrote:
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.
============================================
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

Digital automotive tach circuit?
 

Noozer wrote:
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.

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.

Digital automotive tach circuit?
 

"Noozer" wrote in message
news:GmQ0h.206269$5R2.25840@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.

http://www.siliconchip.com.au/cms/A_102835/article.html

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.

Digital automotive tach circuit?
 

"Noozer" wrote in message
news:GmQ0h.206269$5R2.25840@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

Digital automotive tach circuit?
 

On Sun, 29 Oct 2006 22:03:50 -0500, "Tam/WB2TT"
wrote:


"Noozer" wrote in message
news:GmQ0h.206269$5R2.25840@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.

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