17-05-2012, 12:36 PM
Arduino Solar Day Night Controller
Arduino Solar Day Night Switch.doc (Size: 406 KB / Downloads: 46)
This is an Arduino controlled light sensing switching unit. Its main use is to control solar lights to turn on when it is dark outside, but it can work in many more applications. This guide will walk you through every aspect of the building process. Prior knowledge of the Arduino unit is not necessary since the code and schematic have been supplied for you. This project would be fairly complex to build without an Arduino; it is a good example of how a microcontroller can make a circuit far less complex, with less hardware trial and error.
Explanation
This project has three main sections, the Arduino unit, the software, and the circuit.
The Circuit is composed of two sections, the light sensing and the power switching. The light sensing part consists of a photo-resistor R4, connected like a voltage divider to R2. Since the resistance of the photo-resistor changes depending on the amount of light that is shining on it, the voltage divider's voltage ratio changes depending on the amount of light present. The voltage going through this part of the circuit is 5 volts dc, supplied from the Arduino board to J4 of the circuit. So the voltage divider is dividing the voltage between the maximum 5 volts, to the minimum 0 volts. The Arduino senses this voltage on its ‘Analog Pin 0’ that connects to J3 on the circuit. This is called “analogRead,” it divides the 0 to 5 volts by 1024 (10 bits, or 2^10) so it can sense a change in voltage as small as .0048 of a volt.