Lighted Switch Controlling LED Fixture

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A/A Fuel GTX

A/A Fuel GTX

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WI & AZ
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Electrician
Just installed a lighted switch that controls an LED non dimmable picture light. The lighted switch seems to be pulsing when the LED is off. I'm assuming it's because of the lighted switch going through the LED circuitry for the neutral connection. Is there any reason to be concerned, like will this damage the lighted switch to the point where it no longer illuminates or can I assure my customer that the pulsing is just a throw back to the disco days and all is fine?
 
A/A Fuel GTX said:
Just installed a lighted switch that controls an LED non dimmable picture light. The lighted switch seems to be pulsing when the LED is off. I'm assuming it's because of the lighted switch going through the LED circuitry for the neutral connection. Is there any reason to be concerned, like will this damage the lighted switch to the point where it no longer illuminates or can I assure my customer that the pulsing is just a throw back to the disco days and all is fine?
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If the "light" element in the switch is neon, it will not have any noticeable effect on its life.
If it is incandescent (not likely) then it will burn out sooner.
The pulsing suggests that it takes some time for the voltage to build up to the conduction threshold of the LED input circuit.
A much more troublesome problem would be pulsing of the picture light itself.
 
The picture light works fine. It's a P&S Decora lighted switch so I assume it's neon. I also assume that this scenario will not adversely affect the LED itself?
 
A/A Fuel GTX said:
The picture light works fine. It's a P&S Decora lighted switch so I assume it's neon. I also assume that this scenario will not adversely affect the LED itself?
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The LED is what I would be more concerned about, but not sure if it will cause any harm or not, am leaning toward probably not though. Placing any other (linear) load parallel to the LED load would make the pulsing stop, even if just a small resistor.
 
kwired said:
The LED is what I would be more concerned about, but not sure if it will cause any harm or not, am leaning toward probably not though. Placing any other (linear) load parallel to the LED load would make the pulsing stop, even if just a small resistor.
Click to expand...

Like lets say a 56 ohm, 1/4 watt resistor on the switch terminals?
 
Then that is not what I would call a "small" resistor in this context. :).
With 120V applied across it, it will do a fair imitation of a fuse. Possibly with violent results.

Sometimes a small resistor in effect has to be a large resistance.

Tapatalk...
 
GoldDigger said:
Then that is not what I would call a "small" resistor in this context. :).
With 120V applied across it, it will do a fair imitation of a fuse. Possibly with violent results.

Sometimes a small resistor in effect has to be a large resistance.

Tapatalk...
Click to expand...

Assuming it could handle the heat, it wouldn't really be all that small and that resistor would draw 257 watts @ 120 volts, probably not a great idea to use that one.
 
131125-2349 EST

Try a 0.22 ufd 600 V Mylar or similar capacitor as a load in parallel with the LED lights. The reactance is about 11,000 ohms at 60 Hz. If the pilot light is a neon bulb, then it may have a 100,000 ohms series current limiting resistor. I have not experimented with a neon bulb in series with an 120 V LED or CFL, and therefore I have no idea how it reacts.

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131127-2414 EST

Just tried a neon pilot light in series with a Cree LED 9.5 W bulb, also a CFL. The neon showed an extremely small flicker. Nothing like on and off. You have to look close to see any indication of a flicker. If you are not looking for some sort of variation you would classify this as no flicker.

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131128-1100 EST

This morning I made an LED pilot light from a Stanley EFR5366X high brightness LED shunted with a reversed biased 1N4148 diode and in series with a 680,000 ohms 1/4 W current limiting resistor.

With this LED pilot light and either the Cree or a CFL bulb as the load there was no detectable flicker over a short period of time. The RMS current thru the bulb is on the order of 0.2 mA.

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131130-0901 EST

A/A Fuel GTX:

Following are answers to some of your questions. But first, if I were the customer I would not tolerate a new installation of a device that flashed or flickered when it is supposed to produce a steady light. Also I am not sure why you need a lighted switch for this application.

From post #1, "The lighted switch seems to be pulsing when the LED is off. I'm assuming it's because of the lighted switch going through the LED circuitry for the neutral connection."

I assume your lighted switch is a two terminal device, and that when the switch is in the off position the switch is to light so it can be found at night in the dark.

In this case there has to be a path for current flow to provide power to this indicator light. That path has to be thru the load. It also may require some minimum voltage to turn on. A sample I tested required about a 90 V RMS sine wave. I might have expected a somewhat lower value because an NE51 initially ionizes at about 70 to 90 volts and glows at about 50 V. Less than the about 50 V level and conduction stops. Note: a 90 V RMS sine wave has a peak voltage of about 127 V. Neon bulbs or other ionized gas tubes must be supplied from an approximate constant current source, or after ionization occurs a very large current will flow and burn out the tube. About 1 mA produces good output from an NE51. We can expect your light switch to require something in the 1 mA range.

Still in post #1. "Is there any reason to be concerned, like will this damage the lighted switch to the point where it no longer illuminates"

This won't hurt the lighted switch whether it is a neon or LED indicator. Quite unlikely that it is an incandescent because of the short life, and some other reasons.


From post #3. "I also assume that this scenario will not adversely affect the LED itself?" fixture.

For a lighted switch you want the least power dissipation when the switch light is on, and therefore the current at 120 V is very low. The current from this lighted switch is so low that it won't damage any normal load that would be attached to this switch, your LED illuminated display. And it won't make that display light. That the current pulses is of no consequence.


From post #5. You would not want to put a resistance across the switch terminals. Instead you would want a small added load across the normal load (Your LED display). Small load means not much power, therefore, a moderately high resistance or reactance.


Do bench experiments with your lighted switch and various loads to see what happens. Make some current measurements using a 1000 ohm 1/2 W resistor and measure the voltage across the 1000 ohms. 1 V equals 1 mA. This resistor will reach its power rating at 22 V, or 22 mA. Resistors are inexpensive compared to meter fuses. Thus, using voltage across such a resistor to measure current where you might accidentally apply an over current is a better solution than using the meter current range.

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