Raspberry Pi HAT Is an Electric Vehicle Charger Controller

Microcontroller-based electric vehicle chargers are commonplace. The OpenEVSE project provides a starting point. Nick of Geppetto Electronics has taken the next step by creating a Raspberry Pi EVSE HAT (EVSE stands for electric vehicle supply equipment). Previously Nick created the OpenEVSE II project, which is a refined version of the original. His design separated the high-voltage and low-voltage circuits into separate PCBs. It turns out this arrangement works to the advantage of the Raspberry Pi EVSE HAT.

The HAT provides low-voltage control circuits like the pilot generator, a current transformer (for current sensing), a ground fault interrupter, and an on-board ADC to detect incoming voltage. The HAT relies on the non-real-time nature of an operating system, which means, it cannot rely on interrupts for safety devices. To accommodate this concern, Nick designed the Pi EVSE HAT's ground fault interrupter circuit to gate the power relay in hardware. This method means it does not matter what the operating system is doing if a fault occurs.

Instructions on his Raspberry Pi EVSE HAT project page explain which GPIO pins the HAT needs. Along with the instructions, you can also find schematics and PCB files to build your own HAT. Or, if you are not up to fabbing your own, you can buy both the HAT and HV boards from Nick's Tindie Store.