NOISE - NOISE - NOISE

Noise spikes on power supply or signal lines can easily debilitate a microcontroller or other digital device. Noise spikes caused by DC motors or servos can be enormous. We suggest a number of steps to alleviate this problem.

Good wiring practices: Use a separate power supply to supply the microcontroller! If possible keep motor associated circuitry completely separate from the microcontroller by use of optoisolators.
Also, use sufficiently heavy wiring for high current devices such as motors & servos, and if feasible, use twisted pairs of color coded wires to connect e.g. the battery to the motor control circuitry.

Make generous use of decoupling capacitors (typically 0.1m F disk capacitors) across the supply pins feeding IC's such as digital multiplexers or op-amps. This will greatly suppress noise on their supply lines. In fact, it is highly recommended that you buy a generous supply of 0.1 mF disk capacitors (they're cheap if you buy them in quantity from a mail order place such as Jameco or DigiKey), and make generous use of them throughout your undergraduate design lab career! I've seen many circuits go from "not working - I don't know what's wrong..." to "It finally works!" simply by strategically placing a few decoupling capacitors in the circuit.

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