If you want to use FreeRTOS on LPC2148, then please refer FreeRTOS series.
In our next tutorial, we will see how to interface the Sound detecting sensor with LPC2148 (ARM7).
If Light Intensity is high, it turns OFF the LED and If Light Intensity is Low it turns ON the LED. This source code will control the LED, based on the Light Intensity.
The LDR would be used to measure the light intensity which then adjusts the camera shutter speed to the appropriate level. LDRs can be used to control the shutter speed on a camera. An example of this could be a street light or a garden light. The most obvious application for an LDR is to automatically turn on a light at a certain light level. The figure below shows the curve between Resistance Vs Light Intensity curve for a particular light-dependent resistor. When an LDR is kept in a dark place, its resistance is high and, when the LDR is kept in the light its resistance will decrease. These devices depend on the light, when light falls on the LDR then the resistance decreases, and increases in the dark. This makes the electrons jump from the valence band to conduction. These photons in the incident light must have energy greater than the bandgap of the semiconductor material. It is nothing but, when the light falls on its surface, then the material conductivity reduces, and also the electrons in the valence band of the device are excited to the conduction band. This resistor works on the principle of photoconductivity. That means, In the daytime, the output resistance will be less compared to nighttime. Resistance will decrease when the light increases. These resistors are often used in many circuits where it is required to sense the presence of light. When the light falls on the resistor, then the resistance changes. It is one type of resistor whose resistance varies depending on the amount of light falling on its surface. This article discusses in brief about what is a light-dependent resistor, how to interface with LPC2148.Īn LDR or Light Dependent Resistor is also known as a photoresistor, photocell, photoconductor. Hence, we can utilize the light sensor circuit for automatic switch OFF the loads based on daylight’s intensity by employing a light sensor. This is not only risky, however, additionally leads to wastage of power with the negligence of personnel or uncommon circumstances in controlling these electrical appliances ON and OFF. The dominance of street lights, outside lights, a number of indoor home appliances, and so on are typically operated and maintained manually on many occasions. Before starting this tutorial we should know the below topics.
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