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Electronic components are included in the category of light sensors are as follows: - LDR - Photo Transistor - Photo Diode - Infrared Receiver The function of the electronic component is to detect the intensity of light received by the component. The light sensor is often used in electronic equipment such as on television, light a light switch, light intensity measuring instrument.

OVER LIGHT DETECTOR Here i am going to Introduce you an Excess light Detector or sensor circuit. The sensing component used in this circuit is LDR (Light Dependent Resistor). LDRs are sensitive, inexpensive and readily available device. They posses good power and voltage handling capacity similar to an ordinary resistor. CIRCUIT DIAGRAM OF OVER LIGHT DETECTOR Components required to wire up this circuit 1. LDR 2. R - 1K 3. SCR 4. Buzzer 5. 5V BATTERY WORKING PRINCIPLE OF OVER LIGHT DETECTOR The LDR is a variable resistor whose resistance decreases with increase in light intensity. When the light falling on an LDR has normal intensity, its Resistance is large enough and the voltage across R is insufficient to trigger the SCR. However, when light falling on LDR is of large intensity, the Resistance of LDR falls and voltage drop across R becames large enough to trigger the SCR. Consequently the buzzer sounds the alarm. It may be noted that if the strong light disappears the buzzer continu...

Basic circuit of the LM35 are made to control the fan is either used on amplifier that requires automatic cooling. Its use on power amplifier circuit above and only requires DC fan. From basic sensors based on ic and amplifier op-amp is added again to the transistor Q1 to drive the fan. Part List : R1___220K R2___100K R3___3K3 R4___22K R5___1M R6___150R R7___2K2 R8___33R 4W C1___100pF D1___1N4148 IC1__7915 IC2__TL072 IC3__LM35 F1___DC Fan 12V

The pressure sensor (MPX4100) MPX4100 is a pressure sensor that is equipped with signal conditioning circuit and temperature calibrator makes this sensor stable against temperature changes. For this sensor measurement accuracy using micro-machine techniques, thin film metalization and bipolar semiconductor process. With the signal conditioning circuit, this sensor can connect direct on Analogue to Digital Converter. Signal conditioning circuit generate analog voltage with Full Scale (Full Scale) to 5 Volt. This sensor has the ability to detect the pressure of 15 to 115 kilo Pascal and work under pressure difference between P1 and P2. P1 or Pressure Side consists of gel fluorisilicone that protect it from the objects hard. Pressure sensors on robotic applications are often used as feedback mechanic in which the system microcontroller can detect mechanical condition at the time it. For example to detect strong or weak grip of the robo...

The RS-455-3671 sensor used in the Automatic Rear Bicycle Light project published in  the July/August 2010 edition can be replaced by a motion sensor that costs nothing instead of a fiver or thereabouts.   The replacement is a homemade device, built from components easily found in the workshop of any electronics enthusiast. Effectively it works as a variable resistor, depending on the acceleration force to which the device is  submitted. A prototype presented a resistance of 200 kΩ when not moving, and 190 kΩ when dropping about 1 cm. Constructing is easy. Cut off a piece of about 10 mm of copper tubing. Take a piece of conductive foam, the kind used to protect integrated circuits. Cut a rectangular piece of 10  x 50 mm. Roll up firmly until it can be push-fitted securely into the copper cylinder. Then insert a conductive wire through the centre of the cylinder, bend it and (optionally) add protective plastic sleeving to each side. This is the first contact. Finally, solder a thin wire...

Here is an ultra-sensitive fire sensor that exploits the direct piezoelectric  property  of  an ordinary piezo element to detect fire. The lead  zirconate  titanate  crystals  in the piezo element has a property to de-form and generate an electric potential plifier with gate protected p-channel.  MOSFETs in the inputs. It has high speed  of  performance  and  low  input current requirements. There are two inputs—the non inverting input (pin 3) connected to the piezo element through diode D7 (OA71) that carries the volt-age signal from the piezo element and the inverting input (pin 2) that gets a momentarily changes the voltage level at pin 3 of IC1 and its output swings high. Transistor T1 conducts taking the reset pin 12 of IC2 to ground. IC2 is now enabled and start oscillating. With the shown values of the oscillating components C3 (0.22) and R8 (1M), when heated, thus converting the piezo element into a heat sensor. Pyroelectric Fire Sensor -Circuit-Diagram The circuit we  have  d...