Cigar lighter receptacle
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The car cigarette lighter socket that most automobile drivers and passengers are familiar with is properly called a cigar lighter recepacle, since it was originally designed as a lighter for cigars—hence its rather large size (and unheated center barely large enough to light a cigarette).
These sockets were not originally designed to provide DC power, and are not an ideal DC connector for several reasons, notably the fact that three sizes exist (one for 6 V DC and two for 12 V DC) and the mating of the different sized 12 V DC plugs and jacks is problematic. Because of this, and the small gauge wiring sometimes used, they can sometimes provide only unreliable and current-limited power connections.
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[edit] Technical details
These sockets can be unreliable and the power connections they provide are limited to low current, but they are ubiquitous. Plugs often include a pilot light to indicate a connection has been made. The sockets and mating plugs are officially defined in the ANSI/SAE J563 specification.
For the 12-volt systems, the "contact point," which is the center part of the plug when viewed end-on, carries the positive voltage, whereas the "can" part, which is the outer part of the connector, carries the negative voltage (which is the "ground" connection for most American automobiles, which have a negative ground electrical system).
[edit] 6 volt cigar lighter receptacle and plug
- Receptacle inside diameter: 21.34 mm to 21.46 mm (median 21.4 mm)
- Plug body diameter: 21.08 mm to 21.23 mm (median 21.155 mm)
[edit] 12 volt cigar lighter receptacle and plug, size A
- Receptacle inside diameter: 20.93 mm to 21.01 mm (median 20.97 mm)
- Plug body diameter: 20.73 mm to 20.88 mm (median 20.805 mm)
- Most often used in American automobiles.
[edit] 12 volt cigar lighter receptacle and plug, size B
- Receptacle inside diameter: 21.41 mm to 21.51 mm (median 21.455 mm)
- Plug body diameter: 21.13 mm to 21.33 mm (median 21.18 mm)
- Most often used in European automobiles, and sometimes as a second socket in American automobiles expressly for DC power connections.
[edit] Issues using for power
Since the cigar lighter socket was designed to heat a cigar lighter, using these sockets as power connectors can lead to many problems. In addition to the issues with incompatible sizes, plugs can vibrate out of the socket under normal driving conditions, owing to poor retention. There have been reports of melted plug tips. [1]
[edit] References
- Standards And Specs For In-Seat Power On Aircraft Still In The Clouds discusses mechanical and electrical deficiencies of using the cigar lighter socket for power.
- SAE J563 (Six- and Twelve Volt Cigar Lighter Recepacles)
- SAE/USCAR-4 (Standard for Cigar Lighters and Power Outlets) (USCAR=United States Council for Automtotive Research)
- SAE J563 task force meeting minutes (Password protected)
