I am planning to install a group of level 2 charging outlets at the condo development where I live.
I think it would be great if a user could plug a cord into his/her car and have the system automatically know which car it is.
It might be ideal to use NFC or Bluetooth but those approaches seem kind of complicated. Here is an alternative thought:
1. Equip the J1772 plug handle with a Dallas Ibutton receptacle and a red/green LED.
2. Use 5-wire EVE cable and use the 5th wire for comms using "1-wire" protocol
3. The user keeps a 1-wire key on a lanyard inside his charge door
User's experience: Plug in cord, tap key to reader pad on handle, look for green light.
What do you think?
iButton is a NFC device that uses the 1 Wire protocol.
If integrating the reader out on the J1772 handle, I would be concerned with the distance and running parallel to AC for so long. I am not sure it would work well so far away.
Integration of a card reader and authorization process into OpenEVSE would be a significant amount of work and require back end support as well to track users and usage. Note if you used the Wattzilla C3 UL board, the firmware is locked so adding control for the iButton would difficult and may require re-certification of the firmware with UL if certain portions of code are modified.
I think a Raspberry Pi Kiosk with a Reader (NFC, RFID, iButton) would be a better approach. you could send RAPI commands to the charging station to enable/disable etc.The Raspberry Pi would also pull usage from the Charging stations to match up with the ID. Wattzilla C3 already supports the RAPI command set so no modification would be required. The Pi could also coordinate current usage to ensure your circuit is not overloaded.
Here is a tutorial for adding NFC to a Raspberry Pi.
I'm definitely on board with using an RPi (possibly as a Django web app) for usage tracking, authentication etc. Planning to use RAPI for charger control, and for the load management task to also run on the same RPi. I don't particularly want to mod the OpenEVSE boards.
For my load management plan, I need to get the signals from a couple of panelboard current transformers into the RPi. Pi has no native A/D, so maybe use adafruit ADS1015 breakout.
I still like the idea of ID reader in the J1772 handle, but I am cooling off on the iButton approach as there is exposed metallic contact and corresponding safety concerns. My favorite idea at the moment is using infrared-remote components. 38kHz IR receiver in the handle, drive the raw baseband data down the 5th wire, and couple it to the RPi for decoding. Some little IR-generator circuit (adafruit Trinket?) attached inside the charge door of each car pumps out an ID code which is seen by the IR receiver in the J1772 handle.
I need to think thru the isolation requirements if I want to keep everything on the RPi side Class 2 (per electrical code).
If you are using the ESP8266 Wifi module, you could have the user ID variable post to the OpenEVSE emoncms site. You could then do some post-processing to correlate the user with the KWh used from the server side data. Just a thought.