/challenges-projects/element14-presents/b/blog/posts/how-to-build-an-arduino-controlled-led-matrixArduino Retro LED Matrix Handheld element14 Presents | AirborneSurfer's VCP Profile | Project Videos The matrix circuit for Project Hawthorne is a little different in that it's all NPN transistors instead of the "simpler" combination of a s...en-USTelligent Community 12