====== Noise reduction ======

Noise is the  unwanted disturbance in an electrical signal. It is considered to be a source of error.

===== Main Sources of Noise: =====

  * 60Hz AC supply. This is almost always present.
  * Inductors.
  * Motors and varying magnetic field.
  * RF, Wifi, and Microwave.
  * Anything that causes abrupt change in current (switching regulators and switches).
===== Why we care =====

  * It affects the operation of the system.
  * It could introduce error when measuring or using very low signals (in mV range). The noise could appear on both the signal and power line.

===== How we fix it: =====
  * Use a filter (band-pass or band-stop).
  * Keep inductor’s traces short and fat.
  * Battery power generates less noise compared to regulated power from main source.
  * Use filter/decoupling capacitor. Maybe use a combination of 0.1uf, 1uf and 10uf to handle multiple noise frequencies. Low capacitance handles high frequency noise very well.
  * Add ground planes and Vcc planes.
  * Avoid right angle traces on board design. Especially for high frequency signals, use 45 or curved traces.
  * Keep like components close to each other.
  * Use a split Vcc (analog Vcc and Digital Vcc)
  * Do not cram components too close.
  * Zener can help handle spikes in the circuit.
  * Keep radios away from inductors as much as possible.