David Johnson-Davies USB Power Delivery Dongle Gives Configurable Juice in a Compact Footprint

Maker David Johnson-Davies has designed a compact board for anyone looking to turn a USB Power Delivery (PD)-capable power supply into a user-selectable fixed voltage for their breadboard projects and more: the USB-C Power Delivery Dongle.

"This is a small board that will deliver one of six fixed voltages from a USB-C power adapter that supports [USB] Power Delivery," Johnson-Davies explains of the gadget. "It's compact enough that you can put it in line with a USB-C cable, encapsulated in a small case or heatshrink tubing, and you can select the voltage by soldering a wire link or fitting a jumper in one of six positions. A green LED indicates when the output is active."

USB has long been a handy way to power devices, but early versions of the standard were limited in just how much power they could provide — topping out at a fixed 5V and up to 500mA. Later revisions introduced the ability to increase the amperage, but it wasn't until the launch of the USB Power Delivery standard and later USB Programmable Power Supply standard that the voltage could be adjusted too.

Johnson-Davies' power adapter takes advantage of this, but simplifies matters: the board handles all negotiation of voltages, based solely on which jumper is closed. Users can pick between the standard 5V or negotiated voltages of 9V, 12V, 15V, 18V, or 20V, using either a permanently-soldered link or a moveable jumper. Space for a resistor on the rear allows for a configurable amperage, with Johnson-Davies recommending the dongle for up to 2.25A.

"If the voltage and current combination you have selected isn't available from the power adapter it will provide the closest available lower voltage," Johnson-Davies notes. "So, for example, Apple USB-C power adapters typically offer 5V, 9V, 15V, and 20V. If you request 12V from one of these adapters you will get 9V, and if you request 18V you will get 15V. The voltages and currents provided by an adapter are usually shown on a label on the side of the adapter."

More information is available on Johnson-Davies' blog, while Eagle-format design files and Gerber production files have been published to GitHub under an unspecified license.