Using an Arduino Mega 2560 to read Tesla seat controls and power the motors through a 16 relais board. Building my own playseat.
Please excuse my less-than-pretty procedural code, I've not done this in a while, as I normally work with Functional or OO languages. I might clean this up in the future, but probably not, since this is a hobby project ;P
WARNING: Please be mindful when messing with seat cables and harnesses, the airbag in a Tesla seat is an explosive device! On modern Tesla's these connectors are colored yellow. Prevent applying any kind of power to airbag at all times!
Tesla has excellent wiring diagrams available for free on their website. You do need to create a (free) account. All Tesla models and model years available. I used the Model X wiring diagrams for my seat.
Tesla seat controls are incredibly simple. Each button has a resistor and is connected a signal line. There are 12 buttons on my Tesla Model X driver's seat, and 3 signal lines. I'm using the board in reverse (no problem, since resistors are passive), supplying 5V to the GND of the seat control keyboard, and measuing on the signal lines using the ADC's.
Each signal line is connected to an ADC input of your arduino through a voltage divider to ground. Google "voltage divider", it's basically one extra resistor to ground. The keyboard is our Vin and has an unknown resistance (depending on which buttons you are pressing. We're measuring at Vout. There should be a known value resistor between the measuring point and ground, set this in the code, I used 1k Ohm resistors.
I couldn't get the seat module in my driver's side seat to function. I guess it needs a CAN or LIN connection to do something. I decided to cut the seat module out of the seat, and just drive the seat motors directly. I decided to do this with a cheap 16 relay board, allowing me to drive up to 8 DC motors.
Using mosfets or even ESC's might be a better idea, but I kept it simple.
The code is setup so that each motor direction has a pin, so for the 7 motors in my seat I require 14 pins / relais.
A relay does not simply switch between "off" and "connected", but switches between side A: "Normally Closed" and B: "Normally Open". On my relay board I have connected all "Normally Closed" sides to 12 volt negative/GND, and all "Normally Open" sides to 12 volt positive/PWR.
When I need to turn a motor, I close one of the relays. Close relay 1: turn in a direction, close relay 2: turn in the other direction.
When no relays are turned on, everything is grounded. In theory you could switch the sides around, because the motors won't turn either when everything is connected to 12 volt positive/PWR. But usually car's are chassis negative, so I stuck to that, since this reduces the chance of shorting something.
The head rest on my seat does not have a dedicated button in the seat controls because Tesla's seat module automatically raises the headrest when moving the seat backwards (and vice versa). I might implement a custom button in the future, or imitate Tesla's feature if I implement the seat position sensors.
I haven't got around to this yet, but all motors have hall sensors, so could possibly be read by an Arduino. You could implement seat memory with this.
Not implemented.
Not implemented. Though easily possible with the existing relays. Would only have "full power" or "off". For regulating heat you'd need to read the seat temperature sensors and use mosfet's / PWM signals to modulate the heat. Relays are not suited for repeated fast switching due to a limited lifetime.