LED tach?

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=36428
Printed Date: May 11, 2025 at 4:29 AM

Topic: LED tach?

Posted By: lilboi
Subject: LED tach?
Date Posted: July 29, 2004 at 7:21 PM

I just had a brain storm after looking at the wire diagram for the matrix rsx3.5

It requires you to tap into the tach wire. So can you make LED digital tac by tapping into that wire? that would be cool. Have a line of about 10 led's, one for each 1000 rpms. ever time you rev, it jumps up and down. Think this is possible?

Replies:

Posted By: TheSaint421
Date Posted: July 29, 2004 at 7:40 PM

if you were to take a digital multimeter, and hook the black lead to a ground, and the red lead to one of the tack wires, either in the cluster, or off the coil etc... it would register somewhere between 1V - 6V, and by increasing the RPM it would increase by 1V approx. so it wouldn't be very accurate without some sort of chip to regulate it. so if you just rigged up a few LED's you wouldn't have a clue as to what the actual RPM was, you would just know that it's turning over.

hope that helps... Mark

Posted By: lilboi
Date Posted: July 29, 2004 at 8:35 PM

so the difference between 1000rpm and 7200rpm (my redline), is only 1 volt difference? or 1volt per 1000 rpm?

I'm thinking have one resistor to each led, therefore when it revs, and the threshold is met, it will light up.

Posted By: TheSaint421
Date Posted: July 30, 2004 at 1:05 AM

it doesn't quite work that way, more RMP doesn't mean more pwr. just if you rev it up it will go up by about 1V, and thats if you were at 1500, or 6000.

Mark