A wireless push-button in the charging plug that opens the vehicle's charge port

The task

When you charge an electric vehicle, you open the charge port door first and then reach for the plug. One vehicle manufacturer has changed that: pressing a button on the plug opens the door by radio, and your hand stays on the cable. For the plug manufacturer, this means that a part which used to be purely mechanical and electrical now contains radio electronics.

Brugg eConnect wanted this function in its plugs to the North American standard. The electronics had to fit the contour of the plug grip, transmit without dropouts in the harsh environment of a charging cable and be UL certified for the North American market. The first generation used a magnetic switch for the button; the new one was to be a genuine push-button with feedback.

The solution

The electronics sit on a rigid-flex circuit board made of two rigid sections that follow the grip: one carries the button and LED, the other the radio transmitter with its antenna, with the flexible link in between. The antenna is part of the board itself and was tuned to the geometry of the plug, because a grip made of plastic and metal shapes the radiation differently from a lab breadboard.

The transmitter IC has one-time programmable memory. During development, the firmware therefore runs only in the chip's RAM, and only the released version is written to the chip as a programming image. A qdTest test fixture contacts every board, measures the current draw, checks the function and programs the transmitter only once the test has passed, all in one pass. No chip is programmed with an untested version.

Component selection followed the UL requirements for the target market from the start, and radio testing took place in an accredited lab. Busse Design und Engineering developed the housing and the ergonomics of the grip; we developed the electronics and their testing. Both sides were aligned in iterations until the layout and the grip contour matched.

The plug is UL certified and in series production. What we delivered: feasibility, hardware including antenna design, firmware, the test fixture and test sequence, the certification documents, and support through UL certification into manufacturing.