Breadboard Power Supply USB

The YwRobot MB102 breadboard power supply also has a female USB socket, which suggests that it provides a +5 V output. Here is a sketch of the circuit diagram based on a continuity check using a digital meter. This is how the USB socket, switch, and the voltage regulators appear to be connected. This is not the complete circuit diagram but it gives some clue as to how the USB socket operates. Interestingly, if you were to feed +5 V through the USB socket, instead of using the barrel socket, then that will energise the 5 V rail of the breadboard, and there will also be +3.3 V output. This functionality only works when the switch is in the IN position.

Is the USB Socket for Input or Output?

I tested the USB socket output by feeding 7 V into the barrel socket and measuring the voltage at the USB socket power pin. To my surprise, I discovered a regulated 5.1 V output. This suggests that the designers have purposefully designed the USB socket to provide an output, because it is providing a regulated output.

Double Check

The manufacturer may change the specification without any notice, therefore if you are lucky or unlucky -- as the case may be -- to buy one of these, double check all the voltages with a meter first before you connect it to anything.

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