Computer interfacing via Universal Serial Bus (USB) ports, in either 12Mbps (Version 1.1) or more recent 480Mbps (Version 2.0) offerings, has deservedly become such an indispensable connection method that it’s hard to realise USB has only been in use for just five years.

Here's Stan's prototype USB breakout "box", potted in some hot-melt glue. The idea is to poke your multimeter probes into the terminal block (avoiding shorts) for voltage measurements; for current measurements, you remove the header pin shorting block and connect your mulitmeter in series.

Apart from seamless "smart" data connections for digital cameras, flash RAM dongles, WiFi adapters, modems and mice, etc, the availability of a regulated 5V DC supply at relatively generous currents has also lead to such diverse "dumb" devices as mobile phone chargers, coffee cup warmers, cooling fans and inspection lights.

Dumb, of course, refers to the hi-tech USB data lines (middle pins 2 and 3) being ignored and just the low voltage DC being exploited at (outer) pins 1 and 4.

The PC’s USB port can supply up to 500mA @5V; however, downstream ports on USB devices are generally limited to 100mA maximum.

Although it may be considered frivolous to use a $1000 PC to just power a light or charge batteries, the computer may be on anyway and equipment powered by the 5V USB supply is often conveniently associated with one’s needs at the time.

Cold coffee, when trying to tame a late night spreadsheet macro, can easily ruin one’s concentration!