LOOKING FOR: Individuals who would like to contribute to this project and make it something truly great. Safety, J1772 and IEC62196 conformity and wonderful feature set for the end-user. Published under CC-BY-ND license, because I'd like others to contribute to this project if they would like to implement changes or fixes.

This is the early beginning of a wallbox project for electric vehicle charging. Referencing from openevse.org, I'm using a little different route with the focus on more user-oriented adjustability and better visuals on the display. Interested in using an OLED 128x128 panel (SPI) and letting the user dial the maximum charging current down or up in 1A increments.

Possible power supplies (AC / DC converter) are listed below.

Basic concept

• ATmega328P chipset for Arduino IDE (easy when coding) for the beginning, STM32F0 microcontroller for hosting the system
• 1kHz square wave generator with variable duty cycle, that can be adjusted through an output pin from the STM32F0, a generator with oscillator for perfect frequency stability over time and temperature ranges would be preferred
• Operational amplifier to convert STM32F0 output to ±12V 1kHz square wave (Control Pilot Signal)
• Readback of Control Pilot Signal into STM32F0
• Power Supply -> AC / DC converter from 85-264VAC (47-440Hz) with triple Output: +5V, +15V, -15V (may ±18V)
• Using ±15V/±18V on the power supply instead of 12V so we can fine-tune the voltages with the operational amplifiers onboard to achieve a perfect 12.00V square wave

EVSE modes

• Status A: standby, open resistance, +12V, no square wave
• Status B_noPWM: vehicled connected, +9V static voltage to detect and enable PWM mode.
• Status B: vehicle detected, 2740 Ohm resistance (control pilot - protective earth) +9V(±1V) / -12V, square wave initiated to report maximum charging current to vehicle
• Status C: ready / charging, 882 Ohm (CP - PE) +6V(±1V) / -12V, square wave remains active, vehicle wants to charge, contactor for high voltage lines closes
• Status D: with ventilation (see Status C), 246Ohm, +3V(±1V) / -12V, with the difference that this should shut off, if it's installed in a hot environment and no airflow is provided? (unclear)
• Status E: no power available, 0V/0V, offline, i.e. possibly after Status F until resetting of system
• Status F: Error, -12V square wave amplitude got reduced due to a faulty diode in the vehicle or a human touching the pins

The design shall be as such that it will be possible to use this controller for three-phase 400V power grid in Europe and the 110/220V power grid in North America.

Outputs from controller

• Contactor signal for either a 3-phase contactor or 1-phase contactor depending on the power network/grid
• Protective Earth (PE) for vehicle connector
• Control Pilot (CP) for vehicle connector
• Proximity Pilot (PP) for vehicle connector not required because it is implemented within the plug itself with no feedback to the controller
• OLED 4-pin SPI interface
• UART Debug Console (RX,TX, GND): output only for now

Inputs to controller

• L1 and N from AC power grid (after circuit breakers and GCFI within the wallbox)
• Protective Earth from AC power grid (after circuit breakers and GCFI within the wallbox)
• Rotary Encoder w/ click button
• SWDIO for STM32 ST-Link
• Feedback from Control Pilot
• long-term: current sensor for L1/L2/L3 (is it sufficient to only use one on L1?) for kWh calculation of charging process

Milestones

• 25.06.2016 - created project
• 16.07.2016 - ordered first prototyping PCB (dirtypcbs.com)
• 16.07.2017 - after several further evaluations and learnings, the project has been reworked for STM32F0 chip and a much simpler electronics of creating and evaluating the Control Pilot Signal
• 17.11.2017 - installation of the first prototype into a wallbox, set for 32A, and it's fully working.