Most effective way to control a speedometer


I’m looking for to build a simulator using a real speedometer.

I would like to use Arduino to control on and off the lights like engine light, I believe that I need a switch relay, do I need one for each light/gear?

The wiring driagram is below

Thank you very much,


Looks like the speed signal might be 5V pulses: There is a pin for sending 5V to the speed sensor and another for receiving "signal" (written in Chinese) from the speed sensor. The RPM signal looks to be similar: 5V pulses.

Some of the lights will just need a transistor to switch to Ground. You can tell which ones by connecting the pin to ground to see if the light lights up.

Other lights seem to require a 12V input. That will be trickier. If you can find some tiny relays that will switch 12V DC and have a 5V 30 mA coil you could use those.

The fuel gage and water temperature take a variable resistor, possibly to Ground. Transistors, like used for some of the lights, on PWM (analogWrite()) pins might be sufficient to control them.

Relays get hot when switched too often in short time and are not as cheap as transistors that can switch at very high rate.

You don't need much current to drive the speedometer, signal strength FETs like 2N7777 could do for your 12V.