08-02-2013, 03:20 PM
Sensor
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A sensor is a detector that measures a physical quantity and converts it into a signal which can be read by humans or by an instrument. Mostly sensors are used to sence Light, Sound, Heat , Pressure, Images etc.
In this lesson I will show you many sensors by which you can make many interesting Project.
LDR : Light Dependent Resistance
LDR is a special type of resistance whose value depends on the brightness of the light falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum.
LDR is placed as potential devider circuit so that output voltage will vary according to its resistance or light falling on it.
Thermistor:
Thermistors are temperature sensitive resistors. Two types available NTC( Negative Temperature Coefficient) and PTC(Positive Temperature Coefficient). PTC is used in all kit which uses CRT (Cathode Ray Tube)eg T.V.,monitor in series with Degassing coil. All conductor and semi-conductor resistance is effected by heat. You can use any semiconductor device such as transistor, diode etc as NTC type thermistor. For PTC type thermistor you can use thin wire of many turn for eg you can also use small step down transformers primary connection. Thermistor are inexpensive device.
IR (Infra Red ) Sensor Module
Commonly used in all T.V, DVD Player, DTH etc for receiving Infra red signal from your Remote Control. Today available IR Sensors are packed with little microchips and a photocell.It has 3 pin. Vcc, Ground and output.
Mic (Sound Sensor)
Two types of Mic commonly used Condenser mic and Dynamic Mic. Condencer Mic are small in size used in Head Set, Mobile etc. Dynamic mic is used by DJ, in Music party etc. A speaker will also do the work of dynamic mic.
Voltage Sensor
Zener Diode is used as voltage sensor or as a Voltage regulator. A Zener Diode is a special kind of diode which permits current to flow in Reverse Bias also, when the voltage is above a certain value. This breakdown voltage is called Zener voltage.
Now days e three–terminal programmable shunt regulator diodes are used very commonly. One eg. is TL431 which is very common used in all type of SMPS found in TV, Mobile Charger etc.
For more information Download TL431 Datasheet