The Open EVSE project includes hardware and software for charging electric vehicles and plug-in hybrids using the J1772 standard.A current DIY Open EVSE V4.23 completed board
I started working with the Open EVSE project back in 2011 when I leased my first Nissan Leaf electric car. Chris Howell had started a post on the “My Nissan Leaf” forum and built a few prototype boards to test. Then Lincomatic began working on software and things began to really pick up speed. Chris made the DIY Open EVSE open source on 27 October 2011, and the first boards started shipping in late December.
Unfortunately there was a long waiting list to get the boards, so I decided to make one for myself using the EagleCAD files provided from Chris.
I am still using my original DIY Open EVSE V1 board that I built to charge daily.
Which attests to the quality of the original hardware and software design.
As typical I saw many changes that I wanted to implement to the design to suit my specific needs and quickly began making modifications.
My original V1 board, modified to use a 20x2 Character VFD (Vacuum Fluorescent Display) utilizing a SPI interface.
A V2 board with dual relay outputs and remote LCD display. New in this version was an isolated ±12 volt power module for supplying the pilot circuit, a locking header for the GFCI sense coil connector, and an I2C header with 5volt supply for a remote LCD display.
A popular add-on for the V2 board was the L1 L2 sense board that checked to see if 115V or 230V was being supplied to the system. Level 1 at 115 volts and Level 2 at 230 volts. And also added the ability to check for a stuck relay error condition.
The V3.0 board included an efficient 5 volt switching regulator using a Maxim MAX5033A IC, and also included the L1-L2 sense circuit on the board. A header was also added for a remote LED for those not wanting the added expense of the LCD display.
The V4.0 board introduced the DG419 analog switch which replaced the LF353 op-amp in the pilot switching circuit, and an experimental current transformer and voltage measurement circuit for power monitoring was added. Also included was a header that broke out some of the ATMEGA328P pins.
The V4.21 board added overall stability improvements, and added dedicated regulators for the ±12 supply used for the pilot circuit. The isolated power converter module was changed from ±12 volts to ±15 volts to further improve the DG419 analog switch’s on resistance. The power monitoring circuitry went away, but would reappear in a future design. Lots of bypass capacitors!
The latest V4.23 board includes circuitry to keep up with the SMD Open EVSE firmware. Dual relay drivers are back, along with a solid state relay on board. Also back is the current transformer measurement circuit, and the ability to self test the GFCI circuitry. A new addition was the PP circuit for the J1772 cord. While not as compact as the SMD commercial version, the DIY board allows the hobbyist to easily, not populate non-critical parts of the board not needed for their specific use.
Link to DIY Open EVSE 4.23 Project page.
An add-on for the V2 thru V4.XX boards was the V4.2 display and RTC (Real Time Clock) board. This board uses the MCP23017 I2C 16 I/O port expander IC, and also included a DS3231S RTC IC with a backup battery for precision timekeeping. The board supports RGB backlight LCD displays and includes three current limiting resistors and a contrast potentiometer. Space for I2C pullup resistors along with address selection solder pad jumpers for the MCP23017 are included.