SDG #348 I bought over £30k of LED Lighting to reverse engineer

A pallet of ex-installation architectural LED pixels bought as “parts or not working” turns into a proper reverse engineering exercise. The hardware is Pulsar’s ArcDot2 range: 240 sets of IP65 diecast aluminium RGB dots, an ArcDotDriver80 Art-Net to RS485 controller, and several ArcDotBooster80 28 V power injectors. The listed fault was traced to the usual suspect, leaking electrolytics in the controller’s internal switch mode supply, and separately a dead 75176 differential transceiver on output channel one. A Zener tester confirms the bidirectional protection diode was fine, which is a useful diagnostic order of operations for anyone chasing blown RS485 ports.

The teardown is the interesting part. Each dot uses an MBI5041 16 channel constant current driver with 16 bit PWM, nine PLCC RGB LEDs grouped in series threes, external ballast resistors to shift dissipation off the driver IC, and a buck regulator set to around 10.4 V so long power runs can sag considerably and still work. Best of all, a relay holds the data path in bypass until the local 8051 boots, so a dead node passes data straight through instead of corrupting downstream addressing, a genuinely better design than the shift-by-three DMX pixels covered in an earlier video.

Logic analyser and scope captures reveal a 1 Mbaud UART, 8N1, carrying a break plus 512 bytes of RGB data, so one output can drive 170 dots rather than the advertised 80. Auto addressing is two runs of 160 packets at 25 ms spacing. Frame rate works out near 125 Hz, well within reach of an ESP32 replacement controller.