I have a 50 light LED set. I want to use about 30 of the lights selected at random from the 50.
Question: How can I disable the other 20 lights without cutting wires?
Thanks
Tom B
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The short answer is, you don't. If you're talking about something like Christmas lights. you can't pick and choose without some surgery and potentially some voltage adjustment.
If the string is Christmas lights with the lights in sockets, unplug the lamp from the socket, remove the LED from the lamp holder, replace the LED with a 150 ohm resister,
plug the lamp holder back into the lamp socket. Repeat for each LED you want to
replace. A 150 1/4 watt resistor should work.
When replacing the LED with a resistor, make sure the resistor makes contact like
the LED did.
It is a string of Christmas lights. If one bulb "burned out" naturally, would the other bulbs remain lighted?
Tom B
If one LED burns out half the string goes out. The strings are wired as 2 strings of 25 with one string of 25 LEDs in parallel with the other string of 25.One string lights on half the 60 cycle sine wave and the other string on the other half of the sine wave.
How about black electrical tape, black heat-shrink tubing, or the like around the 20 you want to "disable". As noted above the LEDs themselves or their electrical proxies (e.g., 150 ohm resistor) must be in-circuit for the string to work.
What are the specs on the LEDs? What voltage range do you plan to operate the LED string on? You can't just throw in a random resistor and expect it to work.
If the string of lights are for a Christmas tree than the power source is 115VAC.
The resistor was picked to replace a white LED with the same load and voltage drop
as a white LED. If other color LEDs are being replaced, than a different value resistor could be used. The resistor value is not critical so try a resistor value and check the light output of the string and change the resistor as required.
Originally Posted by pa:
If the string is Christmas lights with the lights in sockets, unplug the lamp from the socket, remove the LED from the lamp holder, replace the LED with a 150 ohm resister,
plug the lamp holder back into the lamp socket. Repeat for each LED you want to
replace. A 150 1/4 watt resistor should work.
When replacing the LED with a resistor, make sure the resistor makes contact like
the LED did.
Sounds like a lot of work just to use an existing string, especially if you have a lot of bulbs you want to remove.
As to the value of the resistor, that would obviously depend on what current they're running the LED's at. If they're running them at other than 20ma, the resistor should technically be a different value.
Thanks guys. I have several strings of these lights, but as gunrunnerjohn points out, it's too much trouble to pick & choose the bulbs that I would want to light by using resistors or even shrink wrap. I won't pursue this idea further.
Tom B
