Internal RGB Lighting Based on Truck RPMs

[Carlospicyness]

Saw this plan on an arduino website, but never the steps to implement it. Any suggestions on how to accomplish this end goal?
My plan:
Read engine RPM (possibly with an OBDII sensor)
Have an LED strip that fills the interior of the vehicle reflect the engine speed by color using an RGB LED. As the engine gets faster, the led fades to different colors.
Example: 
800 rpm = Purple
1500 rpm = Blue
3000 rpm = Green
4000 = Yellow
5000 = Orange
6000 = Red

I want the colors to fade into each other

Any recommendations on where to start would be great.

[W-L]

20 minutes ago, Carlospicyness said:

Saw this plan on an arduino website, but never the steps to implement it. Any suggestions on how to accomplish this end goal?
My plan:
Read engine RPM (possibly with an OBDII sensor)
Have an LED strip that fills the interior of the vehicle reflect the engine speed by color using an RGB LED. As the engine gets faster, the led fades to different colors.
Example: 
800 rpm = Purple
1500 rpm = Blue
3000 rpm = Green
4000 = Yellow
5000 = Orange
6000 = Red

I want the colors to fade into each other

Any recommendations on where to start would be great.

It's going to need some testing but you going to need to find the sense wire that provides the data to the tachometer. It should be fairly simple and be just be a difference in voltage so that would be simple for setting up with an arduino. 

[Dr. KEK]

you can detect engine RPM through the 12v lighter socket, ODBII isn't necessary since you have such broad requirements. you should be able to design a very small PCB with an Atmel chip running the neopixel library to control a few LEDs. 

[Just.Oblivious]

Engine RPM can be read in a variety of different ways.

 

From easy to hard:

- Tachometer signal: square wave signal whose frequency is proportional to the speed of the engine. Easy to work with, minimal hardware required.

- OBD-II: requires additional interfacing hardware.

- CAN-Bus: requires additional interfacing hardware and some reverse engineering.

- Vehicle-specific bus systems (K-Line, IBUS): requires custom interfacing hardware and extensive reverse engineering.

- Triggering on spikes in the 12v system: requires a scope and some signal processing to get anything useful.

 

My custom (Arduino based) HUD uses a combination of the two. Road speed is acquired from a square wave signal going to the instrument cluster, everything else comes in through the proprietary databus (door/window status, key/ignition status, climate control status, steering wheel button interaction, ambient temperature and ambient brightness).