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Science Forum Index » Electronics Forum » Digital automotive tach circuit?
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| Noozer |
 Posted: Sat Oct 28, 2006 6:56 pm |
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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. |
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| Homer J Simpson |
| Posted: Sun Oct 29, 2006 1:53 pm |
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"Noozer" <dont.spam@me.here> wrote in message
news:GmQ0h.206269$5R2.25840@pd7urf3no...
Quote: 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. |
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| Tam/WB2TT |
| Posted: Mon Oct 30, 2006 12:22 am |
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"Noozer" <dont.spam@me.here> wrote in message
news:GmQ0h.206269$5R2.25840@pd7urf3no...
Quote: Anyone have a simple digital tachometer schematic handy?
I want to put a 4 digit LED tach into my van. Resolution of 50rpm is fine.
Fed by the TACH output of a six cylinder GMC on distributor coil.
If it isn't much more difficult, I'd like to be able to drive a bar graph
of 12 to 16 LEDs as well.
Build a frequency counter, and pick the right gate time. I think if you make
the gate time 1/300 of a minute, the display will show RPM/100. Make it
1/30th of a minute (2seconds), and it will display RPM/10. There is a common
coil?
Tam |
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| default |
| Posted: Mon Oct 30, 2006 11:17 am |
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Guest
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On Sun, 29 Oct 2006 22:03:50 -0500, "Tam/WB2TT"
<t-tammaru@c0mca$t.net> wrote:
Quote:
"Noozer" <dont.spam@me.here> 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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