Editing Slip ring (section)

== Types ==
[[File:SlipRings.jpg|250px|thumb|right|The two most common types of slip ring]]
Slip rings are made in various types and sizes; one device made for theatrical stage lighting, for example, had 100 conductors.<ref>Alan Hendrickson, Colin Buckhurst ''Mechanical design for the stage'' Focal Press, 2008 {{ISBN|0-240-80631-X}}, page 379 with an illustration of pancake and drum-type slip rings.</ref> The slip ring allows for unlimited rotations of the connected object, whereas a slack cable can only be twisted a few times before it will bind up and restrict rotation.

=== Mercury-wetted slip rings ===
[[Mercury (element)|Mercury]]-wetted slip rings, noted for their low resistance and stable connection use a different principle which replaces the sliding brush contact with a pool of liquid metal molecularly bonded to the contacts.<ref>{{cite web|url=http://www.mercotac.com |title=mercotac}}</ref> During rotation the liquid metal maintains the electrical connection between the stationary and rotating contacts. However, the use of mercury can pose safety concerns if not properly handled, as it is a toxic substance. The slip ring device is also limited by temperature, as mercury solidifies at approximately -40&nbsp;°C.<ref>{{cite web|url=http://www.moog.com/products/slip-rings/slip-rings-faq-s/ |title=Frequently Asked Slip Ring Questions |publisher=Moog.com |date=2009-06-23 |access-date=2011-09-02}}</ref>

=== Pancake slip rings ===
A pancake slip ring<ref>Peter W. Fortescue, John Stark, Graham Swinerd ''Spacecraft systems engineering'' John Wiley and Sons, 2003 {{ISBN|0-470-85102-3}} page 521</ref> has the conductors arranged on a flat disc as concentric rings centered on the rotating shaft. This configuration has greater weight and volume for the same circuits, greater capacitance and crosstalk, greater brush wear and more readily collects wear debris on its vertical axis. However, a pancake offers reduced axial length for the number of circuits, and so may be appropriate in some applications.

=== Wireless slip rings ===
{{Main|Rotary transformer}}
Wireless slip rings do not rely on the typical friction-based metal and carbon brush contact methods that have been employed by slip rings since their invention, such as those explored above. Instead, they transfer both power and data wirelessly [[Electromagnetic induction|via a magnetic field]], which is created by the coils that are placed in the rotating receiver, and the stationary transmitter.<ref>{{Cite news|url=http://powerbyproxi.com/slip-ring/|title=Slip Rings {{!}} How Does a Slip Ring Work • PowerbyProxi|newspaper=PowerbyProxi|language=en-US|access-date=2016-11-24|archive-date=2016-11-24|archive-url=https://web.archive.org/web/20161124203817/http://powerbyproxi.com/slip-ring/|url-status=dead}}</ref> Wireless slip rings are considered an upgrade from&nbsp;— or alternative to&nbsp;— traditional slip rings, as their lack of standard mechanical rotating parts means they are typically more resilient in harsh operating environments and require less maintenance. However, the amount of power that can be transmitted between coils is limited; typically a traditional contact-type slip ring can transmit orders of magnitude more power in the same volume.