SDG #109 AC LED Dimmer Testing with PCBs from JLCPCB - Lighting Controller Project Part 8

Part 8 of the lighting controller build moves from schematic and layout work to real hardware, with the newly manufactured dimmer PCBs populated and powered up on the bench. The focus is the mains side of the design: phase angle control of AC LED lamps, reliable zero crossing detection, and whether the switching stage behaves predictably across the full dimming range rather than only at comfortable mid brightness.

Measurement is the most instructive part. Probing a mains referenced dimmer safely requires a differential probe rather than a grounded oscilloscope lead, and the captured waveforms show exactly where the conduction angle starts and how cleanly the switch turns on each half cycle. That matters because many dimmer problems only appear at the extremes: buzzing, uneven brightness steps, visible flicker at low levels, or a lamp that drops out below a certain threshold. Viewing the waveform alongside the lamp behaviour makes it clear whether a fault lies in the control firmware, the detection circuit, or the lamp’s own driver.

The practical conclusion for anyone attempting a similar project is that retrofit LED lamps vary enormously in how they respond to leading edge dimming. Some track smoothly, others behave badly regardless of how well the controller is designed, so testing with several lamp types is essential before attributing a fault to the controller board. The episode also shows how well a low cost prototype PCB order holds up for a mains circuit, including clearance, trace width and the general build quality of the delivered boards.