Seven-Cluster Reef Light

Live model of the whole fixture. It runs the same schedule, dimming, button logic, fan control and heat protection as the firmware further down. Change the time, press the five buttons, drag any slider or heat the sensor, and the LEDs, fans and circuit respond.

Circuit diagram

The four shaded areas are the four separate systems: mains to 24 V, high power (drivers and LED strings), fan power, and low-voltage control. LED current only flows in the red area. The ESP32 only sends PWM signals, and the moving dashes on each string show LED current from its own driver. Every ⏚ symbol is the same common ground, returning to PSU −V.

The ESP32 is drawn by function. On the terminal adapter, find each screw terminal by the GPIO number printed beside it. Only 5V, 3V3 and GND terminals carry power, and they only power the ESP32 itself and the two sensors.

Wiring list

Every connection, one per row. Driver terminal names follow the 7-pin 700 mA driver module you chose (IN+, IN−, PWM, LED+, LED−). IN+ and IN− each have two pins; either one works.

Clusters and strings

One driver and one GPIO per cluster, all LEDs in each cluster in series. Night clusters carry the strongest fluorescence colours (royal blue 445 and UV 410) for the evening glow. Day clusters mix royal blue, ice blue 480, a 10000 K white and UV 410 for a blue-rich reef look that keeps corals glowing in daytime too. Clusters sit every 137.9 mm (5.4 in), with 68.9 mm from each end of the 965 mm fixture to the first and last cluster centre.

Control workflow

%%{init: {'theme':'dark'}}%%
flowchart TD
  A[Power on] --> B[All 7 PWM at 0. Pull-downs hold drivers off]
  B --> C[Start DS3231, DS18B20, 5 buttons, serial]
  C --> L{Every 50 ms}
  L --> K[Read buttons B1 to B5]
  K --> T[Read heatsink temperature once per second]
  T --> P{Heat check}
  P -- sensor fault --> P0[LEDs capped 50 percent, fans 100 percent]
  P -- up to 50 C --> P1[LED limit 100 percent]
  P -- 50 to 60 C --> P2[LED limit falls to 50 percent]
  P -- 65 C or more --> P3[LEDs off until 55 C]
  P0 --> S
  P1 --> S
  P2 --> S
  P3 --> S
  S[For each cluster: override or schedule level] --> X[x master x heat limit]
  X --> F[Fade toward target at 25 percent per second]
  F --> W[Write 12-bit PWM at 1 kHz to its driver]
  W --> Fan[Fans: 30 percent while LEDs on, 35 to 45 C ramps to 100 percent]
  Fan --> L

%%{init: {'theme':'dark'}}%%
stateDiagram-v2
  [*] --> Off
  Off --> Sunrise: sunrise start
  Sunrise --> Daylight: start + duration
  Daylight --> Sunset: sunset start
  Sunset --> Night: start + duration
  Night --> Off: night lights off
  state "B1 or B2 pressed" as O
  Daylight --> O: override that group
  Night --> O: override that group
  O --> Auto: next schedule change
  state "Manual hold (B5)" as MH
  Daylight --> MH: B5 off
  Night --> MH: B5 off
  MH --> Off: B5 on, schedule resumes

Spec, power budget and design checks

Every cluster is 5 LEDs, so a plain 24 V supply is enough. A night string (4 royal blue + UV 410) needs at most 18.2 V, typically 16.6 V. A buck constant-current driver needs about 3 V more than its LEDs, so at most 21.2 V, and the sealed 24 V supply leaves 2.8 V to spare with any LED batch. It has no voltage adjustment and needs none.

Bill of materials

Firmware

Install RTClib (Adafruit), OneWire and DallasTemperature from the Library Manager. Written for ESP32 Arduino core 3.x, with a shim so it also builds on 2.x. Every threshold and timing matches the simulator.

Serial commands: status · auto · day on|off|auto · night on|off|auto · peak 3 75 · daylevel 90 · nightlevel 100 · nightend 20 · dayramp 120 40 · master 70 · sunrise 06:00 60 · sunset 18:00 60 · nightoff 21:00 · schedule on|off · dim normal|inverted · fan auto or fan 60 · time 14:30

7-LED test build and power-up order