LIGHT/DARK SENSOR USING SINGLE TRANSISTOR

Circuit Diagram

This is a simple circuit to sense light/darkness. The LDR(Light Dependent Resistor) used in this circuit is used as the sensor. The resistivity of the LDR varies with the brightness of the light. As the brightness of the light increases, the resistance of the LDR decreases and when the brightness of the light decreases, the resistance of LDR increases. Here the transistor acts as a switch.

The components used are given below.......

Q = BC108 or BC548 or BC547
R1 = 10k
R2 = 27k
B = 9v
LED

NoTe:
Adjust the value of R1 and R2 to get much brightness from LED............. :D
You can also use a buzzer or a normal bulb instead of a LED.

TEMPERATURE SENSOR USING SINGLE TRANSISTOR

Temperature Sensor Using Single Transistor

This is a simple circuit developed by me to sense the temperature. The
TERMISTOR used in this circuit is used as the temperature sensor. The
resistivity of the thermistor varies with increase/decrease in
temperature. This circuit is as same as the dark/light sensor. The
difference is, in the place of the LDR(light dependent resistor) i
placed a thermistor.

The components used are given below.......

Q = BC108 or BC548 or BC547
R1 = 10k
R2 = 27k
B = 9v
LED

NoTe:
Adjust the value of R1 and R2 to get much brightness from LED............
You can also use a Buzzer or an ordinary Bulb instead of LED............. :)

TEMPERATURE SENSOR USING TWO TRANSISTOR

Temperature Sensor Using 2 Transistors

This is a simple circuit developed by me to sense the temperature. The
TERMISTOR used in this circuit is used as the temperature sensor. The
resistivity of the thermistor varies with increase/decrease in
temperature. This circuit is as same as the dark/light sensor. The
difference is, in the place of the LDR(light dependent resistor) i
placed a thermistor.

The components used are given below.......

Q1 = BC108 or BC548 or BC547

Q2 = BC108 or BC548 or BC547

R1 = 10k

R2 = 27k

B1 = 9v

LED

NoTe:
Adjust the value of R1 and R2 to get much brightness from LED.
You can also use a buzzer or a normal bulb instead of the LED........ :)

CAPACITOR NUMBER CODING TABLE

Capacitor Code Table

This capacitor number code table will help you to find out the
capacitor values easily.

EASY WAYs TO REMEMBER RESISTOR COLOUR CODE VALUES

There are many mnemonic phrases to help you to remember the order of
the colours:

Black Brown Red Orange Yellow Green Blue Violet Gray White ...
which correspond to the values 0-9.

Black             0
Brown            1
Red                2
Orange           3
Yellow            4
Green             5
Blue                6
Violet             7
Gray               8
White               9

For example: 

Bad Beer Rots Our Young Guts But Vodka Goes Well.

Another example:

B B ROY of the Great Britain has a Very Good Wife .......

This wil help you to remember the order of the colours.................. :D

RESISTOR COLOUR CODING SYSTEM

Resistor Color Code System

The last coloured band is usually used to indicate the tolerance - a
measure of how accurate the stated resistance is, i.e. 1%, 2%, 5%, or
10%. In the case of six band resistors, is used to show the
temperature coefficient - a measure of how much the resistance of a
resistor is changed by changes in temperature.

RESISTORS & ITS VALUES WITH IMAGE

Resistors with their Values

This picture includes the values of resistors with color coding. It
will help you to identify the resistors easily.

Please click here to find the values of the resisrors other than the above........ :)

CLAP SWITCH

Clap Switch

This is a small circuit that acts as a sound activated switch. The ic used is ne555 wich is known as the multi vibrator or timer IC.

Components  :

IC  ne555                        - 1

Transistor   BC547           - 2

Condenser Mic                - 1

Resistor         4.7k           - 1
                     470R          - 2
                         1K          - 1
                       47K          - 1

Capacitors       100n         - 2
                        100uf        - 1

  LED                                - 1

Battery               6V        

NoTe :

You can also use the Transistor BC548 instead of BC547 ...... :)