Christmas 2018 LED string

This year I am using two strings of fifty 5V RGB WS2811 led pixel modules (12mm leds) connected together to make a 6 meter 100 led string.

LED string in place outside

The led strings were bought from Aliexpress and are described as “waterproof IP65”. I am using them outside.

A 50 led string with 12mm leds

I found a few issues with the string. Firstly, when the second length is plugged-in the leds in that string did not fully light with the correct brightness/colours, probably due to voltage drop over the length. I fixed that by running a separate pair of wires to power the second string.

Secondly, the strings have plugs and some bare wires on each end which are not waterproof. I fixed that by wrapping some self-amalgamating tape around the joints.

Here is the schematic diagram:

It is assembled on strip-board and the power supply is a 5V unit rated at 5A.

I am using a separate 5V timer module to turn on/off the display at set times – this plugs in to socket J3 .

Switch SW1 is used to manually turn-on the display and can be permanently connected to ground if no time is being used.

The whole thing is fitted into an old PC power supply case (which is mounted indoors).

Case shown with lid removed

The cable to the LED string should not be too long  (a few meters) as the serial data could get corrupted and the voltage drop may be to great if the cable is very long.


It has 29 effects which are chosen randomly.

These WS2811 led strings have the leds connected in the order Red,Green,Blue (RGB). This differs to the usual WS2812 led strip order (GRB).

Here is the hex file.


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