Thread: Homemade digital tachometer

Props sir props good stuff

Awesome thread, I'm actually working on something similar for my drag car shift light. But i'm running into some problems because the output is only 5v. Have any pointers on wiring up led's in a series and still keeping them super bright? I had considered running the 5v signal to a relay and switching on a 12v circuit to power the light, but I don't know if they even make a relay that will do that. I'm sure that any 5v relay will probably work because I know led's don't draw many amps.

If you want to use a weak 5 volt signal to switch a larger component, I'd suggest using a transistor. Transistors can be used like relays, but require almost zero current to switch on and have no moving parts.

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What signal are you using to control your shift light?

Or you could buy my shift light kit

next you should try to make a digital odometer for our b14 clusters

im so sick of mine not working

Okay, lend me your B14

can you make one with numbers? if so,would you mind doing a write up ...as my tach is dead I would love to make a custom one! and mad props for the project!!!

If you think you can make it work for the b14's, id be willing to give you my b14 cluster for the cost of shipping. Only thing is the rpm and mph reading are a bit off (800-1k rpm off and about 5-10mph off). Not sure if that affects being able to do the conversion or not, but I just thought id let you know. Give the b14 guys a little love too

sure if you can come out to texas

Pretty cool.

I actually tried to use a transistor as a switch but I think I wired it up wrong. I'm using a 5v reference from my megasquirt board. I set the shift point in the software and it sends signal to the pin when I hit that rpm. I've got an led blinker off of a motorcycle that will work awesome and is super bright. I just need to figure out what wire goes where. IIRC the base goes to a 1k resistor then to the 5v on the board, the emitter goes to the 12v light and the collector goes to ground. What I'm confused about is where the ground from the 12v light goes? I assume that the collector and the light share grounds. I'm also confused about the fact that the 12v led set up already contains resistors, etc.