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Creating an EV side pilot control interface to J1772 port

I need to create a simple control interface to be on the EV side J1772 receptacle to provide the pilot to the pilot pin and proximity pin. I have two applications: 15A, 208-240V charging and 30A, 208-240VAC charging. I see from an excellent presentation by Chris that I need to apply a higher resistance between the pilot & ground when I see +12V, then a lower resistor when a 50% duty cycle square wave is seen. Is the proximity indication simply a resistor voltage divider I place on a different pilot pin on the J1772 connector? Is there an off-shelf product to use for the EV side of the J1772 port to control the pilot for negotiation with EVSE as well as the pilot needed for proximity.

Chris, thank you very much for this product info. It looks like it can do the job and makes sense to design this device in long term. Right now, I was hoping for something somewhat less involved. The chargers we presently use are not CAN and are quite low powered, most are just 3kW, so I was hoping to avoid the power reduction feedback to charger and at this point, we don't need many of this EVCC device's functions. For example, we have a fully functional BMS which controls the charger, drive system based on individual cell voltages and performs cell balancing. I was hoping just to have a device that can do the J1772 pilot and proximity feedback. Do you think I can do this with 2-3 small 12V relays and the appropriate resistors or does a simpler device exist?

On the vehicle side... no unfortunately. The pilot is not a negotiation it is a demand. For example the station will tell the vehicle you have 12A available. The vehicle must not exceed 12A. The vehicle side controller must communicate this to the on-board charger via some method. 

The pilot from the charging station can also be dynamic, the station could initially give you a 30A pilot then reduce it to 15A then 6A if there is a power event or power capacity sharing. Again the vehicle MUST comply with the pilot. If there is no communication it would not be possible for the vehicle to reduce charging power on demand.

Proximity is a little different, the circuit is pretty simple. There are 3 states not connected, connected and connected with button pressed. All you need to do is ensure the vehicle on-board charger stops drawing current within 100ms of a button press.

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