# Controlling 30W Pixel Dot **URL:** \ **Category:** LEDs and Multiplexing\ **Created:** [February 14, 2022, 4:35pm UTC](https://forum.arduino.cc/t/controlling-30w-pixel-dot/959121 "2022-02-14T16:35:46Z")\ **Posts on this page:** 1\ **Showing post:** 6
**Author:** ![guyhundere](https://avatars.discourse-cdn.com/v4/letter/g/b9e5f3/32.png) [@guyhundere](https://forum.arduino.cc/u/guyhundere)\ **Post date:** [February 15, 2022, 7:38pm UTC](https://forum.arduino.cc/t/controlling-30w-pixel-dot/959121/6 "2022-02-15T19:38:15Z")
I just realized that since I'm not using the power off the Arduino, I no longer have a common ground. Connecting the ground from the LED to the negative terminal of the external power supply fixed my issue. > [@Common ground and why you need one](https://forum.arduino.cc/t/common-ground-and-why-you-need-one/626215): > > A common mistake for people new to electronics is to have 2 circuits fed from different power supplies with signals passing between the circuits, but with the grounds not connected. This leads to questions asking why the project doesn't work. You don't have to spend long reading the questions on this forum to see this is asked often. Here I attempt to explain the problem and why it matters to connect the grounds. Note that in all of the schematics that follow I have used a battery as a power sup… --- _[View the full topic](https://forum.arduino.cc/t/controlling-30w-pixel-dot/959121)._