94EGCoopey

Car produces 0-12v Square wave reading but the cluster i have needs to see 0-5v Square Wave.

Therefor, my tachometer doesnt work.

Can anyone explain to me how I can drop it from 0-12v to 0-5v coming from the ecu to the tach?

I have read about voltage dividers and zener diodes, but this is all french to me...... I am a pictures kinda of person.

Thanks in advance.

swordofdoom

You will need two resistors to make a voltage divider.
the first one is going to be a 1000 Ohm resistor.
The second one you can figure out from this formula.

[1000 / ( 1000 + X)] * 12V = 5V

Once you solve for X that is the resistor you need.
Solder up one lead of the 1000 ohm resistor to the lead of the X resistor.
On that same lead you solder have it split and also going to your tach that will give u the proper signal. At the end of the other X resistor lead have it going straight to ground.
Make sure you enclose everything so nothing shorts out.

Just hook up your 0-12V signal to the other lead of the 1000 ohm. The formula should be easy enough for you to solve and get all the parts you need to make a cheap voltage divider circuit.

swordofdoom

If your just freaking lazy, get yourself a 3K pot or higher and trim it down from feeding it 12V to 5V using a multimeter to measure the output signal.

94EGCoopey

Thanks man. Went with a 5v voltage regulator. Definitely appreciate your response.

Ray Pip

FWIW, I came across the following voltage divider from AutoZone:

http://www.autozone.com/autozone/acc...er=196559_0_0_

Note that the ad states "Not to be used with electrical gauges." That is probably because the voltage divider is not regulated, i.e., its output is only approximately 6V and has some ripple - not good for some electrical gauges.

I would build my own regulator from an IC on a small circuit board. Both are available from Radio Shack for a few dollars total.

The following is an interesting video on voltage dividers:

Note that if the input is chopped, don't use the capacitors. Use the heat sink if necessary.