The post explains a simple yet effective fish aquarium light optimizer circuit which automatically controls the illumination of a group of appropriately selected LEDs with respect to the varying daylight and after darkness sets in. The idea was requested by Mr. Amit

Technical Specifications

I liked your Automatic 40 Watt LED Solar Street Light Circuit Project, but I am looking is a bit other way round.

1) LDR is in open, broad day light outside the House. 

2) Series of LED (White RED BLUE GREEN ratio (3:1:1:1) is inside the house on the Fish Tank. 

3) As the Day light gets Brighter, the LED glows brighter. 

4) gets Dimmer in evening and Off when Sun Sets. 

5) A low Watt Blue LED Strip depicting calm moon light keeps going when Bright LED are off. 

6) Powered by Solar energy 

7) Can a generic circuit be made with more Solar panels to generate more power and Cater 3 tanks ?
simulating day light is very  important for a marine tank. do you like the concept?

The Design

As shown in the diagram the proposed automatic fish aquarium light optimizer circuit consists of just a couple of transistors as the active components, wherein the NPN device is configured as a common collector while the other PNP as an inverter.

During day time the solar panel produces the specified amount of light conversion supplying the common collector stage with the required amount of voltage.

The NPN transistor base is restricted with a maximum of 12 V with the aid of the connected zener which in turn ensures that the potential across the connected red, blue, green, white LEDs never exceeds this value regardless of the solar panel peak voltage levels.

During dusk when the solar panel light begins deteriorating, the LEDs also experience a proportionately diminishing voltage conditions simulating a proportionately dimming effect in their illumination levels, corresponding to the sunlight....until it's almost dark when these LEDs completely shut off.

In the meantime, as long as the solar panel voltage maintains an optimal voltage the PNP is forced to stay shut off, however as the sun begins to set, the potential at the base of the PNP device begins falling and when it falls below the 9 V mark, prompts the connected blue LEDs to brighten up slowly until these become fully lit after dusk.

The process gets reversed at daybreak, and the cycle keeps repeating simulating a day/night cycle light effect inside the fish aquarium

The 9 V at the emitter of the PNP may be derived from any standard 9 V AC/DC adapter or simply from a cell phone charger unit.

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