How Do Twinkling / Sequencing LED Christmas lights work?

[GasEngineer]

After having a set stop working and fixing a broken wire, I noticed that there are in effect only two wires to each each bulb (positive/negative in and positive/negative out).

I would like to understand how it manages to switch individual and groups of lights on/off and separately flash twinkle etc.

There appears to be a varying DC output from the transformer which may have something to do with it, but all the bulbs are on the same circuit.

Tried extensive googling but can't find the answer. Can someone explain or post a link please?

[Whataguy]

From Siri via chat gpt on the iPhone 16 running 18.2:

Twinkling or sequencing LED Christmas lights with only two wires use a technique called "channel multiplexing." In this setup, the two wires serve as both the power supply and the control signal.

Here's a simplified explanation:
AC Voltage: The lights are powered by alternating current (AC), usually from a standard electrical outlet. The AC signal can be modulated to include both power and control information.
Diode Bridge: Each LED has a diode bridge or similar electronic component that allows it to interpret the AC signal. This bridge converts the AC to DC for the LED while reading the control signal from the modulation.
Timing Circuit: A small timing circuit inside each LED or LED group reads the control signal's modulation to determine when it should turn on or off, creating the twinkling effect.

This design allows for multiple sequences without needing additional wires for each LED, keeping the setup simple and cost-effective.

[Griffith4ever]

They do it in a couple of ways.

Often they'll simply reverse the DC voltage polarity, flip/flop style, and then the LEDs are wired in alternating polarity (LEDs only work when given the correct polarity, and do nothing when given the reverse). So, every other LED it wired the "wrong" way round. Then the controller will pulse 3v + & -, and all the LEDs wired up with + & - will light up, and the ones wired - & + won't. Then the controller pulses 3v - & + , and the other half of the LEDs light up. So you now have discreet control over 2 groups of LEDs.

Add to this a 3rd or 4th wire (still only 2 going to each LED) and you can achieve some very complex effects, by subgrouping the LEDs sveral times again with the extra wires, and the polarity alternation.

[.:ian:.]

Whataguy said:

From Siri via chat gpt on the iPhone 16 running 18.2:

Twinkling or sequencing LED Christmas lights with only two wires use a technique called "channel multiplexing." In this setup, the two wires serve as both the power supply and the control signal.

Here's a simplified explanation:
AC Voltage: The lights are powered by alternating current (AC), usually from a standard electrical outlet. The AC signal can be modulated to include both power and control information.
Diode Bridge: Each LED has a diode bridge or similar electronic component that allows it to interpret the AC signal. This bridge converts the AC to DC for the LED while reading the control signal from the modulation.
Timing Circuit: A small timing circuit inside each LED or LED group reads the control signal's modulation to determine when it should turn on or off, creating the twinkling effect.

This design allows for multiple sequences without needing additional wires for each LED, keeping the setup simple and cost-effective.

That's a terrible and inaccurate explanation, Griffith4evers is much more accurate!

[Whataguy]

You do get a disclaimer on the iPhone results at the moment.

Hopefully we will be able to switch to Grok, iOS is supposed to be allowing the choice of different AI integrations in the future.

[Whataguy]

Groks reply

Here's a simplified explanation of how twinkling or sequencing LED Christmas lights can work through just two cables:

1. # Basic Setup:

- **Two Wires**: The lights are wired in a way where one wire serves as the positive (power) line, and the other as the ground (return) line.

1. # LED Arrangement:

- **Parallel Configuration**: LEDs are connected in parallel between these two wires. This means each LED can be controlled independently without affecting others.

1. # Control Method:

- **Integrated Circuit (IC) or Microcontroller**: Placed somewhere along the string or at the plug:

- **Addressable LEDs**: Each LED or group of LEDs might have its own controller or be part of a chain of addressable LEDs (like WS2812B or similar). These LEDs can receive data signals through the same power wires, which is achieved through:
- **Data Signal**: A very brief change in the electrical signal (like a specific voltage spike or modulation) can be interpreted by each LED or group of LEDs as instructions for what to do next (light up, change color, dim, etc.).

- **Daisy Chain**: The signal travels down the wire, passing through each LED or group, where each one reads the signal intended for it and then passes the rest of the signal to the next LED.

1. # How It Works:

1. **Signal Transmission**:
- The controller sends a signal through the power wire. This signal could be modulated in a way that each LED or segment understands its specific command within that signal.

2. **Command Execution**:
- Each LED or segment interprets the signal, which could dictate brightness, color (if RGB), or on/off state.

3. **Sequence Creation**:
- The controller might send a pattern of signals that correspond to different twinkling or sequencing effects:
- **Twinkling**: Random LEDs light up and go off quickly.
- **Chasing**: LEDs light up in sequence from one end to the other.

4. **Power Management**:
- Since the control signal goes through the power wire, the system must ensure the power delivery isn't interrupted by the data signal. This can be managed by very precise timing or by using the LED's own power needs to momentarily decode signals.

1. # Example (Conceptual):

If you were to visualize this with code, you'd be looking at something like:

```c
void setup() {
// Initialize communication with LEDs
}

void loop() {
// Send command to LED1 to light up
// Send command to LED5 to dim
// Send command to LED10 to change color (if RGB)
delay(100); // Wait for effect
// Repeat with different LEDs for twinkling effect
}
```

This setup allows for complex light displays with minimal wiring, making it both cost-effective and easy to manufacture. However, the exact implementation can vary based on the manufacturer's design choices, including the type of LEDs and controllers used.

[GasEngineer]

Thanks for all the replies - much appreciated.

[phil4]

A lot depends on what sort you're asking about.

The flashing sort that many people have are likely as Griffith4ever says.

A few people have more complex ones, the likes made by "Twinkly", where each LED can display any colour, and be turned on or off individually (called individually addressable), and so display complex patterns, scrolling words, rainbows, plasma etc... these work more like Grok and GPT suggest, using data over the power, to address each LED individually.

[geeks]

Like this:



Mine are 3 wire LED strings with controllers, you have positive, negative and data. The data line tells each "pixel" (a pixel is a single "bullet" that contains 3 LEDs Red, Green, Blue much like the pixels on a TV) to turn on/off/rgb mix