Note: I have checked with the local authorities here in Denmark and it is legal to do this modification as long as the speedometer either shows correct or a higher speed than that which I travel, but illegal to render the speedometer inoperative.
So the project begins:
I have an elderly Mercedes W124 E300D that I am modifying with a newer electronic transmission out of a W210 E320CDI. I have a Powertraincontrolsolutions controller for the transmission, this will control the transmission itself, so that’s covered.
Which leads me to my predicament. I cannot use the speedometer from the w210 model, as I have no clue whatsoever as to how to control CAN Bus or even feed it the correct signals.
I would like to retain the original speedometer/odometer, which was cable driven from the beginning. This cable snaked it’s way from the original gearbox worm drive mounted on the output shaft. That output shaft is missing on the newer gearbox.
So I am in need to control a small DC motor based on the input of a hall effect sensor sitting in the rear differential, IE vary the rpm of the DC motor according to the frequency received from the sensor.
As to my knowledge, the Hall Effect sensor outputs a square tooth voltage from 0-5 volts with varying frequency according to the speed of the input shaft.
This would be fed via an input on the Arduino board, interpreted by it and then sending a PWM voltage to the DC motor either attached to the cable or directly to the instrument cluster itself. Depending on the noise I get from that motor I would opt for using the cable or shortening it somewhat and hiding the motor behind the dash encased in soundproofing or in the engine compartment in a waterproof box.
The reason I chose the Arduino is that I can counter driving with 18" or bigger wheels in the summer and going back to 15" in the winter, correcting as I go instead of having a speedometer that changes display
If possible and this is further down the road I would like for a small 20x2 LCD to sit in the speedometer housing and display some stuff, mainly oil temp, outside temp, boost,
I would even pay for the code, as I know sh*t about coding, and prefer to do the electrics and the mechanical part.
I’ll get a quick and dirty diagram up over the mechanical parts and the electrical connections, so someone with a better mind can point me in the right direction.
Thank You in advance. * Spaceraver