Editing Switch (section)

===Contact bounce===
<!-- This section is linked from [[Elektronika BK]] -->

==== Bounce ====
[[File:Bouncy Switch.png|thumb|[[Oscilloscope]] snapshot showing voltage fluctuations caused by a switch bouncing between on and off (even swinging above V{{Subscript|high}} and below V{{Subscript|low}}) many times over 2.6 [[Millisecond|ms]] before settling|260x260px]]
Contact bounce (also called ''chatter'') is a common problem with mechanical switches, [[relay]]s and [[battery contact]]s, which arises as the result of electrical [[contact resistance]] (ECR) phenomena at interfaces. Switch and relay contacts are usually made of springy metals. When the contacts strike together, their momentum and elasticity act together to cause them to bounce apart one or more times before making steady contact. The result is a rapidly pulsed electric current instead of a clean transition from zero to full current. The effect is usually unimportant in power circuits, but causes problems in some [[analogue electronics|analogue]] and [[logic circuit]]s that respond fast enough to misinterpret the on‑off pulses as a data stream.<ref name="Walker1998">Walker, PMB, ''Chambers Science and Technology Dictionary'', Edinburgh, 1988, {{ISBN|1-85296-150-3}}</ref> In the design of micro-contacts, controlling surface structure ([[surface roughness]]) and minimizing the formation of [[Passivation (chemistry)|passivated layers]] on metallic surfaces are instrumental in inhibiting chatter.

In the [[Hammond organ]], multiple wires are pressed together under the piano keys of the manuals. Their bouncing and non-synchronous closing of the switches is known as ''Hammond Click'' and compositions exist that use and emphasize this feature. Some [[electronic organ]]s have a switchable replica of this sound effect.<ref>Features of Technics E-33</ref>

==== Debouncing ====
[[File:TS contact bounce filter.svg|thumb|right|SPST switch bounce filter using a [[Schmitt trigger]] and capacitor]]
The effects of contact bounce can be eliminated by:
* Use of [[Mercury-wetted relay|mercury-wetted contacts]], but these are now infrequently used because of the hazards of mercury.
* Alternatively, contact circuit voltages can be [[low-pass filter]]ed to reduce or eliminate multiple pulses from appearing.
* In digital systems, multiple samples of the contact state can be taken at a low rate and examined for a steady sequence, so that contacts can settle before the contact level is considered reliable and acted upon. See {{Section link|Keyboard technology#Debouncing}}.
* Bounce in [[#Contact terminology|SPDT]] ("single-pole, double-throw") switch contacts signals can be filtered out using an [[Multivibrator#Bistable|SR flip-flop]] (latch) or [[Schmitt trigger]].
All of these methods are referred to as 'debouncing'.