Frequency varying alarm using LDR and ARDUINO

Frequency varying alarm using LDR and ARDUINO

Author:- M.Sundeep Goud ( sundeep.2488@gmail.com )

              The project is to control the sound in speaker by varying frequency. In this project i used LDR, LED, speaker and ARDUINO to control the frequency. as u can see in the above video the tone(frequency) of  speaker varies as the position of my finger moves between LDR and LED
       

LDR (Light Dependent Resistor)

         
             A light-dependent resistor, alternatively called an LDR, photoresistor,photoconductor, or photocell, is a variable resistor whose value decreases with increasing incident light intensity.

             An LDR is made of a high-resistance semiconductor. If light falling on the device is of high enough frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron (and its hole partner) conduct electricity, thereby lowering resistance.

              A photoelectric device can be either intrinsic or extrinsic. In intrinsic devices, the only available electrons are in the valence band, and hence the photon must have enough energy to excite the electron across the entire bandgap. Extrinsic devices have impurities added, which have a ground state energy closer to the conduction band - since the electrons don't have as far to jump, lower energy photons (i.e. longer wavelengths and lower frequencies) are sufficient to trigger the device.

ARDUINO

                The Arduino Uno is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started.