These differ from J1772 Type 1 connectors in four ways, two of which I'll call out for this discussion:
- They have a locking actuator that the EVSE can use to prevent removal of the plug while charging.
- They can take up to three phase (plus neutral and ground) power, and so typically require a contactor.
OpenEVSE and the Hydra today only have 12 volt DC relay control outputs. So how do you bridge that gap?
This circuit has an input jack and two output jacks. The input jack comes from the Hydra and/or OpenEVSE board and carries 12 volts and a relay output (assumed to be an open collector). The two outputs are an AC contactor switching output and the 3 pin lock actuator output.
The lock actuator is rather simple - there are two lines that are simply fed into a 12v motor. You apply a 12 volt, 300 ms pulse to lock it, and a reverse polarity pulse to unlock. The third line is a switch that is closed when the lock is engaged (the other side of the switch is shared with one of the motor lines).
The circuit above uses an ATTiny85. The controller watches the relay line for changes. On an off->on transition, it will engage the lock, verify that the lock switch is closed, and then turn on the power. On an on->off transition, the contactor is turned off, then there is a brief delay, and the actuator is unlocked.
The circuit above is a 4 transistor "H bridge" for reversing a motor. The bases on each side are pulled up to 12 volts and an open collector driven from the TTL output of the controller is used. This insures that the bases of the H bridge never see other than +12 volts or 0 volts. Intermediate states could potentially turn on both transistors, creating a dead short, which would not be good.
The controller simply raises one of the lines to lock, and raises the other to unlock. To sense the lock state, the controller sets both outputs low and then reads the sense line. That line is configured in the controller as INPUT_PULLUP, so when the switch is closed, the input will read LOW. A zener clamp is used to prevent the full 12 volts from being seen at the controller when the motor is active.
The contactor controller is the same circuit as the contactor adapter I sell in the store today.
The remaining significant difference with the Mennekes connector is the handling of the PP signal. This line should have a resistor to pull it up to +5 and then be fed into an unused analog input on the ATMega. The Hydra has two left - ADC6 and 7. OpenEVSE is not quite so constrained - ADC2 can be used. The trouble is that you'd have to patch the OpenEVSE board both to get to the unused ADC input
as well as pull out the 12 volt power supply (the relay output jack has +12 on it).
Chris is working on a new OpenEVSE board specifically for the European market with all of these items addressed, but if anyone wishes to retrofit their old OpenEVSE, that's what you'd need to do.