LED fixtures

AquasManager drives each channel of a fixture with PWM, from an ESP32 pin or an output of a PCA9685 module.

How it works

The ESP32 outputs a 3.3 V PWM signal, which can’t power high-power LEDs directly. It drives a power stage:

an LED driver with a PWM dimming input (constant-current driver with a “DIM” input);
or a MOSFET module for constant-voltage LED strips (12 or 24 V).

One channel = one controllable colour = one PWM pin = one driver.

Commercial fixtures

Many reef fixtures have a dimming input, or accessible drivers. Check their documentation: the expected signal (3.3 V or 5 V PWM, 0-10 V) determines the electronics needed between the ESP32 and the fixture.

Dimmable power supplies (Meanwell ELG-B, HLG-B…)

These power supplies have two dimming wires, DIM+ and DIM−. Left open, they deliver full power. They expect a 10 V PWM signal, while an ESP32 or a PCA9685 only output 3.3 to 5 V: the fixture would only reach a third or half of its power.

The simplest solution is one optocoupler per channel (a PC817 board, for example):

Control side	Power supply side
input ← PWM output	collector → DIM+
GND ← controller GND	emitter → DIM−

The optocoupler shorts DIM during the pulse: the logic is inverted. Tick Inverted PWM on the channel. Several power supplies on the same channel (two units for the whites, for example) can share one optocoupler: connect their DIM+ together and their DIM− together.

The dimming wires of a power supply that is only used as a 24 V source (for a driver board or MOSFET modules) stay open and insulated.

Common ground

A dimming input without a “DIM−” wire (an LDD driver, for example) reads the signal relative to the driver’s −Vin. Then connect the GND of the controller or PCA9685 to the − of the drivers’ power supply. Never connect anything to the − of the LED output (−Vo): it is not a ground.

Without a common ground, the dimming input “floats” and the driver goes to full power.

Flicker at low intensity

Many drivers become unstable below 5 to 10 %: the light flickers at sunrise and sunset. Set the channel’s switch-on threshold just above that zone (see the Lighting guide). With an optocoupler, a lower PWM frequency (300 Hz for example, in the light settings) also steadies low intensities.

A MOSFET module that chops the output of a power supply set to constant current “pumps” at every cut: prefer a constant voltage supply, with LED strings that limit their own current.

Settings in AquasManager

Declare the fixture, then one channel per colour on its PWM output. Schedules are then set as described in the Lighting guide. The controller needs an RTC clock.