I need advise on the following problem: I am connecting a 5 metres WS2812B based RGB-LED strip to an extension cord. This is a 12V version, where two LEDs are coupled in terms of their addressing and IC. There are 100 addresses and 200 LEDs. I am generating the control signal from a Raspberry Pi.
- I connect the ground of the Pi's GPIO and the ground of the external 12V power supply (a strong 150W laptop power adaptor)
- I connect GPIO 18 out (3.3V) to the DI of the LED strip
- I connect the 12V to the LED strip
- This works
Now I want to insert an extension between power supply and Pi on one end, and the LED strip on the other end. I bought a 3x 0.75mm 20 metres cable for that. (Here is the product description in German if you are curious).
- I inserted two wires between the 12V power supply and the GND/12V pins of the LED strip
- I inserted the third wire between GPIO out and the strip's Digital In.
- This doesn't work
Simply powering the strip seems fine; all LEDs go on. If I run the modulating program on the Pi, the first three or four LEDs are erratically flickering, that's it. Now I tried all sorts of combinations to figure out what is going on. For example,
- I inserted a LLC to lift the digital output signal from 3.3V to 5V. Makes no difference. Does not work.
- I extended only the power but connected the digital signal directly without extension. Makes no difference. Does not work.
- I extended only the digital connection, leaving the power supply directly connected to the strip. This works.
This result was very surprising to me. I kind of feel relieved that I won't have trouble extending the digital signal, but now I'm baffled why the power extension apparently doesn't work. Using a volt metre, I saw that over the 20 m, the voltage drops from 12V to 9V. However, compensating by setting a higher voltage at the adapter, e.g. 15 to 18V to measure around 12V on the other end, did not change the situation.
My question is: What is the reason for this problem, and what should I do to properly extend the power connection by 20 metres? Is this simply a fault of the diametre, or am I looking at the wrong type of cable? Because even a standard 240V euro cable only has 0.75mm diametre. (In German this type of cable is called H03VV-F). The cable needs to work in outside space.