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==Neon indicator lamp== [[image:Neon 5503-2.jpg|right|200px]]
These tiny lights are used as indicators. They've been replaced by LEDs in modern electronics, but are still useful for mains power indication jobs such as light switches that are remote from the [[light]] they control.
They're also used to enable finding light switches in the dark. For this they're wired from switched live to live, so they light only when the main light is off.
===Types=== Indicator neons come in these types of package:
- just the bare neon
- bare neon plus resistor, shrink wrapped
- in small round housing
- in rectangular housing about 13x28mm
- 4 neons with resistors built into a plastic square ring that mounts behnd a light switch
- MK gridswitch part
All of these except the first normally come with built in resistor.
===Mounting=== Ways to mount bare neon indicators: # Drill a tiny hole, and poke the tip of the neon into it # Fit a translucent plastic spacer behind the switch, with built in neons and resistor # Fit a neon in a housing into a suitable round or rectangular hole. These come in the usual neon colours, red, orange, yellow, green. # In some situations its sufficient to simply mount the neon behind a white plastic front, which then glows. Its best suited to dim locations, light output is low.
Round housed neons go through a drilled panel hole, fixed with a nut.
Rectangular housed neons sit in a rectangular hole. Making these holes without a suitable punch is a real pita. The housing simply presses in place. To remove one, compress the 2 plastic fingers that hold it in place.
Light-up switch rings simply sit behind the switch faceplate.
Gridswitch parts fit the MK gridswitch system.
===Resistor=== Indicator neons must be operated in series with a suitable resistor, usually 220k for 240v operation. Failure to do so results in prompt failure. Most neon indicators have this built in, but neons without it are also available. A 240v rating means the resistor is built in.
If providing your own resistor, it must be 400v rated, and typical
0.3w carbon film resistors are 200v rated. Use 2x 120k 200v resistors in series.)==Neon flickering candle lamp== Small imitation candle bulbs, the light sources moves about as it operates. These give out very little light.
==Neon screwdriver== An unsafe voltage detector. See [[Neon screwdriver]]
==Obsolete neon devices== ===Sign lighting=== Neon gas filled shaped tubes were historically once in advertising, coloured to produce red, yellow, orange or green light. Modern coloured tubing is [[fluorescent]].
===Neon lamp=== Long obsolete, neon lightbulbs of a few watts were once used for low level general [[lighting]]. The light is yellow-orange.
===Neon tuning indicator=== A column shaped neon used in some pre-war radios. The height of the glow is proportional to the current through them.
===Neon regulator=== Indicator neons were once used as voltage regulators at about 90v. 3 terminal neons were once used as voltage limiters in some old dial telephones.
==Light colour== The yellow-orange light is a mixture of red, orange, yellow and green light. Colour filters are often added externally to give any of these colours. 'Blue neons' really contain other gases.
==Life expectancy== [[image:Neon black 5578-2.jpg|right|200px]]
Life expectancy of neon lights varies widely, with indicators lasting years, but often not for the life of the product they're in. They last longest in situations where they're not on all the time.
Light output deteriorates a lot over time. The most common failure mode is blackening of the bulb. The neon pictured above still works electrically, but emits no light.
A secondary failure mode is loss of emission. Loss of emission causes [[dim]]ming, flickering, then failure.
Life expectancy to the power of 3.5 is proportional to current, so life can be much increased by reducing run current. A 10% drop in current gives a 44% gain in lifetime.
[[Category:Lighting]]