Sensor

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 sense Light, Sound, Heat , Pressure, Images etc.

In this lesson I will show you many sensors by which you can make many interesting Electronics 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 divider 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.
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. Condenser 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.

Advance Sensors :

PIR Motion Sensor Module (pyroelectric sensor)
Highly integrated module popularly used for entry detection, it complies with micro-controller or DC loads. Output high when motion detected.

Centigrade Temperature Sensor
Its output voltage is linearly proportional to the Celsius (Centigrade) temperature. Eg of this type of sensor is LM35. Programmable type is 18B20.

Project using Temperature Sensor LM35

Hall Effect Sensor
These Hall-effect switches are monolithic integrated circuits with tighter magnetic specifications, designed to operate continuously over extended temperatures to +150°C, and are more stable with both temperature and supply voltage changes. Eg of this sensor are A3141 to A3144.