Coin cell batteries power many an embedded electronics project, and are excellent if you need a tiny bit of power in a compact size. Because of their minimal power capacity–3V in the 200 mAh range for CR2032 batteries, and about half that for CR2016s–if you need to push a device to its limits, swapping them out can get inconvenient, expensive, and non-environmentally friendly. As an ingenious alternative, Bobricius offers the coin cell CR2016/CR2032 battery emulator to allow one to sub in USB power instead!
The device is formed from a printed circuit board, with a rectangular area for a Micro USB connector and other circuitry on one end, and two circular sections on the other. The top circle snaps off, revealing a CR2016-sized section that slides into a typical battery holder. The snapped off circle can then be stacked and soldered on to “fatten up” the adapter for use as a CR2032. Meter connection points are also provided for easy current consumption testing.
The trick to how this device works lies in a few dimensions that work together perfectly. The CRxxyy moniker specifies a coin cell’s diameter as xx, i.e. 20mm, while the thickness is noted by yy, i.e. 1.6mm or 3.2mm. A standard PCB is 1.6mm in thickness, and double that is 3.2mm, matching the CR2016 by itself, or the CR2032 when two are stacked together.
