Electrical Safety

Electricity can be dangerous to either your body or your equipment. The following notes are by no means comprehensive, but please

Arduino Wiring Hazards

  1. Please only rest the Arduino on a non-conductive surface. It has exposed metal on the back which can short-circuit.

  2. Please generally refrain from touching the exposed electrical connections with your fingers. There are no dangerous voltages, but electronics can be damaged from static charges on your body.

  3. Please perform all wiring changes with the USB cable detached and the Arduino unpowered.

  4. Please carefully observe breadboard wiring discipline, double-checking all jumper wire locations.

  5. The most common errors are off-by-one insertions of a jumper wire into a position adjacent to the desired tie point. For this reason, I recommend not using the busses +/- as marked, but instead keeping the +5V and ground busses widely separated.

Arduino Power Hazards

We frequently use a computer as the power source for our Arduinos via the USB port. Occasionally, students have damaged their computers due to wiring mistakes, especially those involving external power supplies. To minimize risk, please observe the following.

  1. Please limit any actuator circuits powered by the 5V bus to only one micro-servo. For multiple micro-servos or DC motors, please use the external 5V power supply in your kit.

  2. The Arduino 3.3V output is drawn from an onboard regulator sourced from the 5V supply. It should not be used to drive actuators.

  3. USB ports have limits on current and most computers will reliably shut down the port if the power draw is too high. If your computer reports an overload, immediately disconnect your Arduino and troubleshoot.

  4. The Arduino 5V output is either drawn from USB or from the barrel plug input via an onboard regulator. Both sources have similar total current limits.

  5. When using an external 12V supply for larger actuators, please keep the higher voltages carefully isolated and triple-check all wiring. Students have damaged laptops in the past by inadvertently shorting +12V signals into the Arduino pins; please avoid this expensive mistake.