Curious Scientist Takes a New Approach to Breadboard Power Supplies with a USB PD "Decoy" Board
Negotiating up to 20V and dropping it down to 5V or 3.3V, this compact breadboard power supply makes additional power available on-demand.
Pseudonymous maker "Curious Scientist" has designed a power supply for breadboard projects, which is based on a USB Power Delivery "decoy" system to deliver on the demands of high-power circuits.
"My aim is to introduce a different approach to the breadboard power supplies," Curious Scientist explains. "The devices I have encountered so far are based on the same 5V and 3.3 LDO [Low Drop-Out] regulators (typically, AMS1117), they have a limited input voltage, and usually, the high voltage that goes to the LDOs is not accessible on the boards. Sometimes they don’t even have a simple fuse on the LDO's output to protect the circuit from overcurrent which is being powered from the supply board."
Curious Scientist, then, wanted a similar power board design — one that connects to the power rails of a standard solderless breadboard to minimize wiring — that didn't rely on LDOs. The solution: USB Power Delivery (PD), to take advantage of the ubiquity of compatible power supplies. The only problem, of course, is that in order to use a USB Power Delivery power supply to its full potential, you need to negotiate for more than the default 500mA at 5V you get by just connecting up a straight cable — which is where the "decoy" circuit comes in.
"The board is powered via a USB [Type]-C cable which is connected to a PD-capable USB charger," Curious Scientist explains. "The voltage requested from the USB charger can be set by a 3-position DIP switch. It can be 5V, 9V, 12V, 15V and 20V," and is then stepped down to 3.3V or 5V. "We [can also] tap into the USB voltage (VUSB trace) and supply it to something power-hungry, such as a motor driver or a larger display."
"Let's say we use a 5V microcontroller and connect a bunch of sensors and a display to it," Curious Scientist continues, "so the total power consumption is 1A at 5V or 5W. We still have 25 or so Watts available on the USB (assuming we use the IKEA charger and we requested 12V). We can add a NEMA 17 stepper motor to the project and use it properly. Or, we can add a servo motor and supply it from the breadboard power supply’s screw terminal specifically made for this purpose."
The project is documented in full on Curious Scientist's website, with the board design files uploaded to PCBWay; additional information is available in the video embedded above and on the maker's YouTube channel.