Circuit Diagram for aa Automotive Tach

[wazzabie]

I'm looking at building my own tach for an HEI system. I've been looking around and found this circuit and information, Anyone else here built there own tach?

This tach can be set up for any number of cylinders by linking the timing resistor. A 500ohm trim resistor is used for final calibration. A protection circut composed od a 10ohm resistor and zener diode is also shown for safety precautions against transients which are to be found in vehicles.

Article about a tach build
http://foz11.tripod.com/DIY_MOD_s/Digital_Speedo/digital_speedo.html

National Semiconductor
www.national.com/an/AN/AN-162.pdf

Nice write up for a VW Bug
http://www.electro-tech-online.com/...06247-lm2917-lm3914-tachometer-schematic.html

 

[Blue85]

A tach is just a frequency to voltage converter, like you show above. The hard part is having a cool display. Personally I wouldn't want to look at a 90 degree voltmeter. What are you going to use?