J1772 EV charging station

What is it?

This is an open hardware / open software J1772 EVSE (electric vehicle charging station).

It was inspired originally by OpenEVSE, but this is an entirely new design that takes a different approach.

It consists of two separate boards. The first board is a logic/display board. It has the controller, pilot generator, GFI, ammeter, clock/timer and most of the rest of the low-voltage systems. It's designed as a "backpack" board to mount on the back of an RGB backlit 2x16 character display. That is intended, in turn, to be mounted on the lid of the standard OpenEVSE enclosure (available from the OpenEVSE store). It connects via a flat-flex cable to one of three HV / power boards. You can choose either the contactor HV board, the external relay HV board, or the internal relay HV board. The contactor board is intended to connect to an external two-pole 208/240 volt contactor rated for however much current you wish your charging station to support. The external relay board is almost the same as the contactor board, except that it's designed for 12VDC relay coils. The charging current rating for both variants depends entirely on the contactor or relay you choose. The internal relay board has two board-mounted SPST relays and the chassis wiring is consequently easier, but it is rated for only up to 24A of charging current.

Note that this product is only the two printed circuit boards (with all surface mount parts pre-assembled for the quick-kit or all parts assembled and tested for the assembled version). To make a full charging station, you must supply J1772 and input power cabling, a contactor (for the contactor variant) or relay (for the external relay variant), a chassis/enclosure, ammeter and GFI coils and various other wiring components. See the documentation for full details.

Why did you make it?

One difficulty with the original design of OpenEVSE is that it mixed high voltage circuitry on the same board as the logic and other low voltage systems. This made it unsafe to attempt to diagnose or otherwise experiment with the board. This design not only separates the HV system on a separate board, but as designed there is a substantial physical distance between the two boards (even so, applying power with the enclosure opened is not recommended). Also, the system is powered from a single voltage DC power supply, with +5 and -12 volts generated with on-board DC-DC converters using inexpensive components. The pilot generator is a four-transistor switching system that works extremely well while being very inexpensive.

What makes it special?

It's compatible with the tried and tested OpenEVSE firmware, compact and easy to assemble into a fully specification compliant and safe charging station.