It can be very convenient to make use of the 5v supply existing in every USB socket for external purposes. This lead brings out the 5v from a USB port to two screw terminals labelled with the appropriate + and - polarity indicators. However, it should be noted that the 5v supply prpvided on USB ports has only a very limited current capability and, although it can theoretically provide up to 500mA, we would not recommend using more than 100mA. It should also not be used to power electrically noisy motors or similar inductive devices due to the possibility of voltage spikes being introduced into the USB system supply. The Majority of sensor modules we stock use no more than 2 or 3mA making this a very easy solution, especially for initial experimentation. The cable is approx 1M long with a USB Type-A connector.