SDG #199 Aquarium Light Controller PCB and MQTT on the ESP32

This episode moves the aquarium lighting project off the breadboard and onto a proper custom PCB built around the ESP32, and it is as much a lesson in real-world board bring-up as it is a build log. The board layout choices are walked through first, including layer stackup, the power section feeding the LED channels and how the ESP32 module is positioned relative to the switching hardware to keep noise away from the sensitive analogue and control lines.

The schematic review is the most useful part for anyone attempting something similar, since it explains why each part is there rather than just showing the finished netlist. Assembly is done with paste and reflow techniques familiar from other builds on the channel, and the honest inclusion of bodge wires afterwards is worth paying attention to: even a carefully checked design usually needs one or two corrections on the first revision, and seeing how those errors are diagnosed and patched is more instructive than a board that works first time.

On the firmware side, the controller is wired into an MQTT broker so the lighting channels can be commanded over the network, which is the sensible route if you already run home automation rather than depending on a vendor cloud service. The first boot, mechanical integration into the light fixture, and a full functional test of the channels together show whether the design actually holds up under load rather than just on the bench. The closing section outlines what needs to change for a second revision, which is the realistic takeaway: treat rev 1 as a prototype and budget for a respin.