Automatic night light using 555 timer

Description 
A cheap and simple  automatic night light using few transistors and NE555 timer is shown here . The circuit will automatically switch on the AC lamp when night falls and the lamp will automatically switched off after a preset time.


The working of this night light circuit very simple. An LDR is used as the sensor here. At day time the resistance of the LDR will be low and so do the voltage drop across it, the transistor Q1 will be in conducting mode . When darkness falls the resistance of LDR increases and so do the voltage across it. This makes the transistor Q1 OFF.  Base of Q2 is connected to the emitter of Q1 and so Q2 is biased on which in turn power IC1.



NE 555 is wired as monostable multivibrator that is automatically triggered at power ON . This automatically triggering is achieved with the help of capacitor C2. The  output of IC1 remains high for   a time determined by resistor R5 and capacitor C4 . When output of IC1 goes high transistor Q3 is switched ON which triggers triac T1 and the lamp glows . A 9V battery is included in the circuit in the order to power the timer circuit during power failures . Resistor R1 and diode D1 , capacitor C1 and Zener D3 forms the power supply section of the circuit . R7 and R8 are current limiting resistors.



Notes:

• The circuit can be assembled on a very board.
• Preset R2 can used to adjust sensitivity of the circuit.
• Preset R5 can be used to adjust the ON time of the lamp.
• The wattage of L1 must nor exceed 200W
• Heat sink is recommended for BT136.

for more information about 555 timer IC

more information about 555 IC

Silicon Controlled Rectifier

What is SCR ?

It is Silicon Controlled Rectifier , use in power electronic device. It use as a switching devices in many high voltages area and high temperature .

figure shows physical diagram and symbol of SCR.
SCR is well known member of thyristor family, although there are many different members are available in thyristor family but SCR are so widely used that as if thyristor and SCR become synonymous.


If we see from the constructional and operation point of view , it is a four layer (PNPN) three terminals (anode,cathode, gate) semiconductor device. This device has two states ON and OFF. We can turn it ON by sending gate current signal between second P layer and cathode. But we cannot turn OFF by control signal. That means we have control upon its turn ON, once it goes to conduction mode , we lose control over it.

It can block both forward and reverse voltage but can conduct only in one direction.It use in high power application like AC -DC converter etc.

SCR V-I Characteristic 

Images electronics figure, circuit diagram chart

Mobile  to Smart phone of popular companies 

Apple

Samsung

Nokia

Lumia series 

old nokia

TV from 1970 to 2015

In 1970

In 1980

In 1990

In 2001

In 2005

GPS

What is GPS ?

The Global Positioning System (GPS) is a satellite base navigation system . It is maintained by united states government and was originally designed for soldiers and army vehicle,but now it available freely to all.  

The satellite work on solar power and also backup batteries when solar light is not available.   

Working principal

There are six GPS satellite in each 4 orbit of earth, they are arrange in such a way that minimum 4 of them cover any point of the globe.

The GPS satellite transmit signals to receivers.

Figure below show how GPS work

Frequency use in GPS

Bluetooth

What is Bluetooth ?

Bluetooth is a smart technology device, by using this device we can communicate or send commands with other devices or near distance peripherals.

Bluetooth use 2.4 GHz frequency.

Why Bluetooth called Bluetooth  ?

Bluetooth was borrowed from the 10 th century, second king of denmark, king Harald , who was famous for uniting Scandinavia just as we intented to unite the PC and cellular industries with short range wireless link.

Bluetooth Protocol

Bluetooth versions 

Bluetooth V1.2

• Backward compatible with v1.1 faster connection and discovery.
• Recovered confrontation to radio frequency interference by avoiding the use of crowded frequencies in the hopping  sequence.
• Data speed up to 721kbit\s.

Bluetooth V2.0

• Enhance data rate for faster data transfer.
• Data speed is upto 3Mbit\s.

Bluetooth V2.1

• Backward compatible with v1.2.
• Uses secure simple pairing to improve a better pairing experience for bluetooth devices.
• Lower power consumption.

Bluetooth V3.0

• Bluetooth 3.0 provides theoretical data transfer speeds up to 24 Mbit\s.
• for high data rate traffic this version  uses the adjacent 802.11 link.

Bluetooth V4.0

• Modified than previous version.
• Provides faster data speed.
• Lower power consumption.
• More secure version.

There are some of simple circuit diagram of Blue tooth 

CDMA

What is CDMA ?

 Code Division Multiple Access. This is a communication technology use in 2G and 3G wireless  communication.  As name implies this technology use multiplexing .It use Ultra High Frequency  Band (UHF) 800 MHz to 1.9 GHz .

figure shows different users data is first converted into code and that code is multiply with a uniqe number and than it will be transmitted to receiver , on that side by using that code which we use in transmitter side again multiply so we get our original data on receiver side .
This is a basic multiplying technique.

This figure shows how data is multiply with a unique code on transmitter side and again same process is done on reverse direction.

Advantages

Application 

Tech@electricalindia : Which is more dangerous voltage or current!!!!

Tech@electricalindia : Which is more dangerous voltage or current!!!!

Full form use in electronic

Full form related to Electronics & Computer

• HTTP -  Hyper Text Transfer Protocol.
• HTTPS - Hyper Text Transfer Protocol Secure.
• IP - Internet Protocol.
• URL - Uniform Resource Locator.
• USB - Universal Serial Bus.
• VIRUS - Vital Information Resource Under Seized.
• 3G - 3rd Generation.
• GSM - Global System for Mobile Communication.
• CDMA - Code Division Multiple Access.
• SIM - Subscriber Identity Module.
• AVI - Audio Video Interleave.
• RTS - Real Time Streaming 
• SIS - Symbian OS Installer File
• AMR - Adaptive Multi-Rate Codec
• JAD - Java Application Descriptor
• JAR - Java Archive
• 3GPP - 3rd Generation Partnership Project
• MP3 - MPEG player 3
• MP4 - MPEG 4 Video file
• GIF - Graphic Interchangeable Format
• JPEG - Joint Photographic ExpertGroup
• BMP - Bitmap
• DOC - Document (Microsoft Corporation)
• PDF - Portable Document Format
• HTML - Hyper Text Markup Language 
• CD - Compact Disk
• DVD - Digital Versatile Disk
• CRT - Cathode Ray Tube
• DOS - Disk Operating System
• GUI - Graphical User Interface
• IP - Internet Protocol
• ISP - Internet Service Provider
• TCP - Transmission Control Protocol
• UPS - Uninterruptible   Power Supply
• HSDPA - High Speed Downlink Packet Access
• GSM - Global System for Mobile Communication
• VHF - Very High Frequency
• UHF - Ultra High Frequency
• GPRS - General Packet Radio Service
• WAP - Wireless Application Protocol
• ARPANET - Advance Research Project Agency 
• IBM - International Business Machines
• HP - Hewlett Packard
• AM/FM - Amplitude Modulation / Frequency Modulation
• WLAN - Wireless Local Area Network

Others

1. A.C - Alternating Current
2. AF - Audio Frequency
3. ASll - American Standerd Code for Information
4. ALU - Arithmatic Logic Unit
5. AC - Auxiliary Carry
6. ALE - Address Latch Enable