Maker and former One Laptop Per Child staffer C. Scott Ananian has designed a quality-of-life upgrade for the OpenEVSE electric vehicle charging station, offering a capacitive touchpad and radio-frequency identification (RFID) reader to help keep your charger secure yet allow third party access on-demand.
"This project replaces the original front panel of the OpenEVSE open-hardware EVSE [Electric Vehicle Supply Equipment] charger with a new front panel with a capacitive-touch keypad and RFID reader," Ananian explains of the project. "This allows basic access control for your charger: you can assign PINs and track usage by PIN, keep your charger 'mostly locked' but allow folks who contact you on PlugShare [an EVSE sharing service] to drop by and charge once you give them a pin, etc. For frequent users you can give out RFID cards as well, and track usage by card ID."
The OpenEVSE project aims to deliver an open source alternative to off-the-shelf electric vehicle charging stations, and comes in its default configuration with a design that slots into the Polycase ML-85 weatherproof enclosure. Ananian's mod, though, replaces the printed front panel with a capacitive touch PCB, lit for use at night through "reverse-gullwing" LEDs on the back side.
"I've got three of them running at my house now," Ananian says of the latest revision of the board, which swaps a black solder mask layer for white in order to reduce heat build-up in the sun. "Two for our personal EVs (a [Tesla] Model Y and a Fiat 500e) and one more for public use. We can give out PINs for the public charger when we're contacted via PlugShare, or for neighbors who need a place to charge, which lets us track usage."
Ananian has released the project for others to build, but does warn of a few "bodges" in its design — and the potential to resolve them in a future third revision. "The CAP1214 chip I'm using for the capacitive keypad has only 11 LED outputs, whereas there are twelve keys on the keypad," he explains.
"I hacked around this in v1 and v2 by wiring the 'back' and 'enter' keys LEDs in parallel," Ananian continues, "so both LEDs blinked when you pressed either of them. The second bodge is the more usual 'dumb mistake' kind, where I'd managed to short two traces in the PCB layout in a way that the DRC [Design Rules Check] didn't catch; hence the 'green' (actually orange) wire running from U3 to the capacitive pad for key '3.'"