Cigar lighter receptacle

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The car cigarette lighter socket or car adapter that most automobile drivers and passengers are familiar with is properly called a cigar lighter receptacle, since it was originally designed as a lighter for cigars — hence its large size and unheated center that make it less than ideal to light a cigarette.

These sockets were not originally designed to provide electrical power, and are not an ideal power connector for several reasons, notably the fact that three sizes exist (two for 12-volt DC and one for the older 6-volt DC systems) 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, the power connections they provide are sometimes unreliable and not suitable for high-power devices.

Despite these limitations, they are often used for many purposes; for example, electric razors, portable spotlights, laptop computers, mobile phones, PDAs, USB adapters, digital audio players, lamps, or even thermoelectric coolers. For devices that run on regular line voltage, a plug-in inverter will convert to alternating current, and transform it up to 120 or 240 volts AC. Inverters have become so popular that some larger vehicles (minivans, pickup trucks, SUVs, and especially recreational vehicles) come with them built-in, along with domestic AC sockets.

Low-power devices that run on even lower voltages can be plugged into these sockets by using a DC/DC converter. Universal ones have a switch that allows selection of 3, 4.5, 6, 9, and 12 volts. Some instead supply 5 volts to a USB "A" socket, allowing USB devices to be used or recharged. Likewise, the USB socket has become the cigar lighter socket of the computer world, with dozens of unrelated devices now using it for power, especially because of its ubiquitous connector (unlike the many sizes and voltages of coaxial power connectors).

Contents 1 Lighter 2 Plugs 3 History 4 Technical details 5 Issues using for power 6 See also 7 Notes 8 References 9 External links

[edit] Lighter

The lighter is a cylinder containing a thin coil of nichrome wire, through which high current (15-20 amps) passes when the device is activated, usually by pushing its handle in. When pushed in, the lighter is held against the force of a spring by a hook attached to a bi-metallic strip.^[1] The heating element becomes glowing orange hot in seconds, causing the bimetallic strip to bend and unhook the mechanism, and the handle pops out. If the lighter is then promptly removed from its socket, it is capable of setting cigarettes, cigars and tinder (among other things) on fire.

In newer cars, the socket often ships without the heating element (the "lighter") due to declining popularity of smoking^[2] However, the socket continues to exist to power consumer electronics in cars as the primary purpose. Often, a vehicle may come with several outlets for convenience, such as for powering portable GPS devices, recharging cell phones, powering a tire pump or a vacuum cleaner from an outlet in the trunk (boot) or rear hatch. These usually have a plastic cap tethered to them, and are usually labeled as not for lighters, as they are not designed to take the heat generated by them.

[edit] Plugs

12 volt automobile plugs are regulated by UL 2089, vehicle battery adapters. This standard covers plugs and cord sets that insert into cigarette lighter receptacles. In Europe 12 volt plugs and sockets are regulated and require approvals, see "E mark" for requirements

[edit] History

Cigar lighters started appearing as standard equipment in automobiles in 1925 or '26.^[3] In 1928 the Connecticut Automotive Specialty Company in Bridgeport patented the first automotive cigar lighter with cord and reel. The modern "automatic" automotive V-Coil lighter was developed by Casco in 1956.^[4]

In the reel type lighters, the igniter unit was connected with a source of current by a cable which was wound on a spring drum so that the igniter unit and cable could be withdrawn from the socket and be used for lighting a cigar or cigarette. As the removable plug was returned to the socket, the wires were reeled back into it. The circuit was closed either by manual operation of a buttom of by withdrawal of the igniter from its socket. ^[5]

In 1921, the Morris patent (no. 1,376,154) was issued for a so-called "wireless" or "cordless" lighter. This ligher eliminated the cables and the mechanism for winding and unwinding them, it provided for heating the lighter unit without removing it from its socket, and it eliminated all electrical and mechanical connection of the igniter unit with the socket once it was removed therefrom for use. ^[6]

[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).

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)

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.

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.^[7]

A second problem is that "12 volt" power in cars is subject to wide fluctuations. Although the battery produces approximately 12 V, an operating engine supplies 13.5–14 V to charge the battery.^[8] A load dump transient can produce very high voltages. A car receiving a jump start from a truck will be subject to its 24 V electrical system.^[9][10] (This "double battery jump-start" abuse is performed by some tow truck drivers in cold climates.)

[edit] See also

• DIN 4165 connector
• CASCO Lighter History (1925 - 1960)
• CASCO Lighter History (1960 - 2005)
• Large Photo of Receptacles

[edit] Notes

[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 Receptacles)
• SAE/USCAR-4 (Standard for Cigar Lighters and Power Outlets) (USCAR=United States Council for Automotive Research)

[edit] External links

• Pictures of 12 volt plugs and Sockets