Here are the most common issues and solutions…
- Double-check all wiring. Are the clock and data wires swapped? Is ground connected to the Arduino?
- Confirm the Arduino is connected to the INPUT end of the strand.
- Check power supply polarity and voltage. Are + and - swapped? If you have a multimeter, confirm 12V DC output (±10%) from the power supply.
- Are the power wires at the opposite end of the strand insulated or trimmed? They should not be left exposed where they might make contact with metal, or each other.
- Is the correct board type selected in the Arduino Tools→Board menu?
- Double-check all wiring. Are the clock and data wires swapped? Is ground connected to the Arduino?
- Confirm the Arduino is connected to the INPUT end of the strand.
- Is the correct board type selected in the Arduino Tools→Board menu?
- Did the strandtest code successfully compile and upload?
- Confirm that the number of LEDs in the Adafruit_WS2801() constructor match the number of LEDs in the strand (both will be 20 if using the strandtest example and a single strand of LEDs).
- This can happen when trying to power too long of a strand from one end. Voltage will drop along the length of the strand and the furthest pixels will “brown out.” Connect power to every 20 pixel strand.
- Confirm the library is unzipped prior to installation.
- Confirm the library is properly named and located. The folder should be called Adafruit_WS2801, and placed inside your personal Documents/Arduino/Libraries folder — not inside the Arduino application folder!
- After installation, the Arduino IDE needs to be restarted for new libraries to be used.