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Led Diode String

ruko

New Member
I have string of LED holiday lights that are either on all together or can be set to blink randomly. There are two wires going in to each LED and two wires going out. Parallel right? What confuses me is one LED can be off and the next in line can be on when random blinking is chosen. How is this possible with only two wires going in and two going out?
Thanks.
 

Diver300

Well-Known Member
Most Helpful Member
Strings like that are often wired with alternate LEDs in reverse. If the polarity is one way, the odd-numbered LEDs light up, reverse it and the even numbered ones light.

If the polarity is alternating, all the lights will appear to light.

Depending on the frequency of the alternating current, there may be visible flicker.
 

ruko

New Member
Thanks. Makes sense. The string is hooked to a solar cell/battery combo with a control box that controls what the diodes do. The box must generate the alternating current since it is not connected to AC house power.
 

Diver300

Well-Known Member
Most Helpful Member
Thanks. Makes sense. The string is hooked to a solar cell/battery combo with a control box that controls what the diodes do. The box must generate the alternating current since it is not connected to AC house power.
It is the box that generates the AC. It can't be simple mains frequency as it wouldn't be controllable.

It needs 4 transistors to control what is effectively 2 strings of LEDs. If there were more wires, it could be done with fewer transistors but that would cost more in wires.
 

Pommie

Well-Known Member
Most Helpful Member
Or they could be addressable LEDs such as WS2812s but unlikely unless an expensive set of lights that can do far more than blink.

Mike.
 

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