Coming in under the “very useful for some” banner is this USB to Banana Jack adaptor for laboratory power supplies. Whilst we all probably have some form of USB socket or charger within reach standard USB sockets are exactly that, standard, and tend to only offer whatever flavour of USB power they are designed to supply. That can be a frustration if you are building devices or systems with USB supplies and you need to test with varied conditions.
This adaptor in essence is pretty straightforward. It connects a USB to a pair of 4mm Banana Jack sockets which are a common connector for benchtop power supplies. This means that you can dial in the voltage and the current supplied to the USB connector. Whilst this means you need to take care not to over-volt and kill an attached project, it does mean you can have a USB supply with all the bells and whistles and safety features of your benchtop supply. Even most budget variable supplies can perform constant voltage current regulation and we aren’t too ashamed to say that we often use it as a rough measure of current consumption by an attached circuit.
The adaptor allows for the data lines to be connected via a switch and also has a jumper socket to which you can attach a resistance that defines the maximum charge current available at the USB.