Aquarium Lighting! Pt. 1

My aquarium is fully planted:

I have a Finnex Planted+ 24/7 RGB LED light – the W/R channels provide the necessary light for photosynthesis while the G/B channels allow for colour mixing, to give a sunrise/sunset cycle. The trouble is, the timing for this cycle is fixed and there’s no way to vary the photoperiod – which is actually a bit long for my tank and leads to algae buildup. So I’ve had to keep the light on a timed socket to reduce the photoperiod, which sadly means no more sunrise/sunset cycle. If only I had a better way to control the light…

I’m looking at moving to a longer tank, which will need a new light. Commercial options run at about $250 minimum for the LEDs and controller – if only I had a decent controller I could use cheaper LEDs!

Commercial LED controllers (for example the Phillips Hue) are cheaper, but still a bit pricey – and don’t give the flexibility I’m looking for. So I’m planning to build a custom 4 channel light controller. It will need to interface with the existing LED strip in the Planted+; after some poking around I’ve found that the microcontroller in the light supplies +15V to the LEDs and runs PWM switching to ground.

The controller will be based on a Raspberry Pi 3, because I had one lying around and it will allow for easy wifi updates of the light program. I’ll design a PCB to be printed cheaply (e.g. SeeedStudio) and plug directly into the RPi – the circuit will mimic the existing low-side switching arrangement. The whole controller will be powered by two SMPS’s – 25W@5V for the RPi and 70W@15V for the LEDs. The existing power supply is rated for 15W@15V, so this should allow for almost 3x the light level.

The total project cost should be under $100 (plus a bit of work) and will allow for much more flexibility than a similarly-priced commercial option.

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