The DIY Open EVSE Project

The Open EVSE project includes hard­ware and soft­ware for charg­ing elec­tric vehi­cles and plug-in hybrids using the J1772 stan­dard.OpenEVSE4.23topA 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.

OpenEVSEboardV1populatedMy orig­i­nal build of the DIY Open EVSE

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.

GLC-OpenEVSEchargingMy orig­i­nal V1 board, mod­i­fied to use a 20x2 Character VFD                        (Vacuum Fluorescent Display) uti­liz­ing a SPI interface.

OpenEVSEboards2012Some of my ear­ly DIY Open EVSE boards from 2012 up to the V3 board

OpenEVSEboardV2populatedRly2A 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.

OpenEVSEv3brdThe 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.

OpenEVSEv3PStest1Testing the new 5 volt switch­ing reg­u­la­tor cir­cuit with var­i­ous loads, and ver­i­fy­ing effi­cien­cy and rip­ple voltage.

OpenEVSEv3PStest2 Voltage out 5.061 volts with 6.2 mV ripple.


P1040001The 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.

OpenEVSEv42brd1The 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!

OpenEVSE4.23topThe 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.

8607767074_ef7a63eeac_oAn 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.

DIY Open EVSE V4.23 board installed in enclo­sure and ready for EV charging.

Eagle CAD V7.5 schemat­ic and board files for OpenEVSE DIY V4.23
PDF for DIY Open EVSE con­nec­tion diagram

Bare boards are avail­able from OSH Park fab­ri­ca­tion service:
OpenEVSE DIY V4.23
OpenEVSE 4.2 dis­play and RTC

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