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Bargraph Voltmeter

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Llamarama

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Hello all, I've started designing a digital dashboard for my car and nearly have it sorted.

I would like a tachometer bar that curves around the speedometer display (Similar to that of a Toyota Supra MA70). Cutting a long story short, I would like 5 LEDs on to represent 1000RPM at 200RPM intervals up to 6 or 7000RPM.

I thought I could use several LM3914s chained up each representing 2000RPM on 10 LEDs each in bar mode. However this appears to not be possible.

The main things I need are bar mode, 200RPM intervals and only easy to use off the shelf components (No fancy LED drivers or microcontrollers please, they scare me.)

Thank you for any help with this.

*EDIT* It's worth noting that I plan to use the LM2917 Frequency to Voltage converter, obtaining 1V per 2000RPM. Hence the need for a bar graph voltmeter.
 
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I'd do it digitally. Since you don't want to use a uC, how about some CMOS counting logic. There are various sensors under the hood that make pulse frequency proportional to engine revs per unit time. We would need to determine an appropriate gating period for the counting, and the output of the counter could light one of 7 LEDs directly, with no decoding.
 
What pulse rate can you easily get from the engine sensor? How many pulses per crankshaft revolution?
 
I'm using a lead coiled around the HT lead from the distributer, though a Hall sensor and magnets may work also. As I'm running a 4 cylinder I get a signal every 2 rotations of the crank. I think anyway. As its from the HT lead it should be good till the engine starts to misfire so it's really Dependant on the engine type, but the engines I'm going to use this on (Ford Pinto and then ported to a Rover V8) redline at 5500 - 6500RPM so this method should be good to about 7000RPM.
 
If you are using the center HT lead, then two (out of four) plugs fire per rotation. I dont like messing with the HT, especially connecting it to wires that come through the firewall. Great source of ignition noise for your car radio, etc.

Can you find a low-level logic signal (like the magnetic pick-up) that fires your distributor rather than messing with the HT?
 
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