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Power from a Computer with USB

Many commercial products such as phones, MP3 players and cameras take their power from a computer’s USB port (when connected) and school projects can also do this. This is a great power source, especially for small devices as it saves on bulky batteries or the expense of a mains adapter.

Boat Race

Miniature Race Boats by Fernwood School.

Which Resistor Should I Use with my LED?

LED brightness is controlled using a current limit resistor to drop some of the battery voltage, calculate the resistance using the formulas in this guide. A worked example shows the calculation used to work out the resistance to accompany an LED in a typical circuit using a 9V battery.