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J1772 - Type 1 'Charger'/Wallbox

 The wall boxes for charging EV's aren't actually chargers, they are just a fancy 240v (some can also be 3 phase) outlets. 

The protocol is pretty simple, and can be found on Wikipedia. https://en.wikipedia.org/wiki/SAE_J1772

There's basically 2 signal lines, Pilot Proximity and Control Pilot, the control pilot is a 1 khz PWM signal, where the duty cycle represents the maximum current the car is allowed to draw. The proximity pilot is a fix resistance, one of 2 values. On denotes the plug is connected, another that the release button is pressed so the charger can immediately stop drawing current and so stops arcing.

Inside the wall boxes are simply a EVSE protocol controller, an RCD, possibly a GFI and a relay/contactor. They are insanely expensive for what they are, so I've designed a simple circuit board that makes use of an Arduino Pro Nano, a cheap and widely available micro controller and a simple program that implements the bare minimum of the protocol. 

The code and board design files are here should you want to take a look https://github.com/jamiejones85/BigPieEVSE

I take no responsibility for anything you choose to do with the design for the board or the code.




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