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First and foremost, let me say that I'm new to electronics and the Raspberry Pi. I'm a programmer. I have never done this type of project before.

Now, I have a Raspberry Pi 3 model B that controls my 150 LED strip. This is powered by a 5V battery pack which outputs 2.4 amps per USB port. The Pi outputs 3.3V at its GPIO. I need to convert the voltage with a voltage level converter chip; the TXB0801 to be precise.

Last week everything was working fine with this layout:

The pattern that the Pi was sending to the LED was 100% correct. Now, I wanted to add switches for the power to the LEDs. When I tested the switches, nothing worked anymore. I reverted back to this same design (without the switches), and now, the LEDs are acting wonky. It's basically random colours now with no distinct patterns.

While troubleshooting I tried tons of stuff:

  • Replaced the voltage level converter
  • Replaced all wires
  • Bypassed the first LED on the strip (maybe the first LED was broken) and connect to the second LED on the strip
  • Checking 100 times at the wiring is correct
  • Checked the code, it's 100% correct

Now, I tested something today. I tried to not use the chip (volt level converter) at all. The data from the Pi is connected directly to the data of the LED strip. The pattern seems a bit better, but, get this, when I hold the connection of the data wires with my fingers, the pattern is now correct. It seems that with my body, the pattern is 100% correct. What can I do to make this work like it did before? Did I blew something with the switches?

  • I don't know how the circuit ever worked! The voltage level converter chip will NOT switch 150 LEDS. You need a different solution. Why not just use a MOSFET? – Milliways Oct 16 '17 at 0:46
  • @Milliways Well, it worked before as I have video proof. Why would it not switch 150 LEDs? – Alexandre Demers Oct 16 '17 at 2:53
  • The max current of the level converter is 150mA. Unless the (unspecified) device you used has onboard drivers you need MOSFET drivers, which is the situation with most LED strips. You have provided very little information with your question and how it is wired is unclear. – Milliways Oct 16 '17 at 2:59
  • Post a link to the LED strip your using. Usually one end is data in and the other end is data out - did you swap it round ? – CoderMike Oct 16 '17 at 15:33
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I found the solution. In my second setup, I used telephone solid core wire. That was the only "variable" that was different from my working solution. Now everything works. Thanks for your help.

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