thats cool.
i am planning to built below circuit.can u guys tell me what components shld i change to make it work on 12v(12-15v) supply.
http://members.tripod.com/~foz11/DIY...al_speedo.html
just name the components i'll modify the diagram and will provide eagle board so that other can make one easily.

 

The circuit in your your new link will bpow up the 7.5V zener diode voltage regulator at pin 9.

The circuit you had needed a 12V or higher supply. It also needs to have a 10k ohms output pot because the 350 ohm pot is dragging its supply voltage way down.

It is very important to know if you have breaker points or a swinging magnet thing called variable reluctance as an input to determine if you have the correct IC.

__________________
Uncle $crooge

 

thanks for the reply guru
my vehicle uses CDI ignition system.so i am sure i'll be getting pure sine wave.
and it will be great if some one could give me the rough diagram of LM2917,LM3914 powered with 12v supply
forgive me if i sound dumb
regards

 

If your car doesn't have breaker points (nothing to do with CDI ignition which also could have breaker points) then it has a low level AC input and you should use the LM2917-8 which has only 8 pins. The LM2917 with 14 pins has a positive input only for use with breaker points.

Get the tachometer working before adding an LM3914 display.

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Uncle $crooge