Comparing the value read from the A/D converter connected to the photoresistor with that connected to trimmer R39, the micro decides whether to start the sequence of fading, or whether turn off the LEDs. RGB LEDs are driven by the transistor; this choice permit to control with a single line of microcontroller, more LEDs in order to create large luminous figures.

As you can see, we use a line dell’ATmega for each of the primary colors of red, green and blue, so it is clear that all the diodes will do the same play of light. Of course isn’t required to mount all the LEDs provided in the circuit: you mount those who need to obtain a good visual effect on the size of the pattern in the Plexiglass. Note that there are three terminals on the PCB: one to connect the power switch (ON / OFF) a second (BATT) to apply to the circuit power supply and a third (CHARGE) for a possible battery charger lead or a small 12-volt solar panel, which already incorporates the charging circuit. These solutions allow you to use the figures lack the power grid. In this regard, an analog input of the microcontroller is dedicated to control the battery voltage: when it drops below 10 V, the circuit will emit flashes to warn that the energy is about to end.

This circuit is evidently intended to be used externally (provided it is properly isolated) and will turn on and off independently, thanks to the ambient light sensor, which will illuminate the figures in the evening to let off in the morning. In short, is a solution to decorate the garden or backyard.

Building shapes

The materials chosen for this application are clear polycarbonate (or methacrylate) or Plexiglas, which can give the shape you want. Then we need to affect, deep enough (half or two thirds the thickness of the plate) the drawing or writing that you want to appear bright.