NIGHT SENSING CIRCUIT

THIS CIRCUIT Is used to sense the night darkness, actually when the night comes and dog begin's to bark, the dog's are having a sense to see through night .

The condenser microphone fitted in the dog’s cage senses barking sound and generates AC signals, which pass through DC blocking capacitor C1 to the base of transistor BC549 (T1). Transistor T1 along with transistor T2 amplifies the sound signals and provides current pulses from the collector of T2.

The input trigger pulse is applied to the collector of transistor T3 and coupled by capacitor C3 to the base of transistor T4 causing T4 to cut off. The collector voltage of transistor T4 forward biases transistor T3 via resistor R8. Transistor T1 conducts and capacitor C3 discharges to keep transistor T4 cut-off. Transistor T4 remains cut-off until capacitor C3 charges enough to enable it to conduct. When transistor T4 conducts, its collector voltage goes low to drive transistor T3 into cut-off state. Resistor R9 and capacitor C3 are timing components. When fully charged, capacitor C3 takes about two minutes to discharge. So when sound is produced in front of the condenser mic, triac1 (BT136) fires and the bulb (B1) glows for about two minutes. Assemble the circuit on a general purpose PCB and enclose in a plastic cabinet. Power to the circuit can be derived from a 12V, 500mA step-down transformer with rectifier and smoothing capacitor. Solder the triac ensuring sufficient spacing between the pins to avoid short circuit. Fix the unit in the dog’s cage, with the lamp inside or outside as desired. Connect the microphone to the circuit using a short length of shielded wire. Enclose the microphone in a tube to increase its sensitivity. Caution. Since the circuit uses 230V AC, many of its points are at AC mains voltage. It could give you lethal shock if you are not careful. So if you don’t know much about working with line voltages, do not attempt to construct this circuit. EFY will not be responsible for any kind of resulting loss or damage.

source : efymag.com

SEISMIC SENSOR

This circuit simulates a seismic sensor to detect vibrations/sounds. It is very sensitive and can detect vibrations caused by the movement of animals or human beings. So it can be used to monitor protected areas to restrict entry of unwanted persons or animals.

The circuit uses readily available components and the design is straight forward. A standard piezo sensor is used to detect vibrations/sounds due to pressure changes. The piezo element acts as a small capacitor having a apacitance of a few nanofarads. Like a capacitor, it can store charge when a potential is applied to its terminals. It discharges through VR1, when it is disturbed.

In the circuit, IC TLO71 (IC1) is wired as a differential amplifier with both its inverting and non-inverting inputs tied to the negative rail through a resistive network comprising R1, R2 and R3. Under idle conditions (as adjusted by VR1), both the inputs receive almost equal voltages, which keeps the output low.

TLO71 is a low-noise JFET input op-amp with low input bias and offset current. The BIFET technology provides fast slew rates. Capacitor C1 is provided in the circuit to keep the differential input of IC1 for better performance.

When the piezo element is disturbed (by even a slight movement), it discharges the stored charge. This alters the voltage level at the inputs of IC1 and the output momentarily swings high as indicated by green LED1. This high output is used to trigger switching transistor T1, which triggers monostable IC2. The timing period of IC2 is determined by R7 and C5. With the shown values, it will be around two minutes. The high output from IC2 activates T2 and the buzzer starts beeping along with red light indication from LED2.

Assemble the circuit on a common PCB and enclose in a suitable cabinet. Connect the piezo element to the PCB using single-core shielded wire. Enclose the piezo element inside a rustproof, small aluminium box. The piezo element should be firmly glued to the enclosure facing the fine side towards the case. Fix the sensor assembly on the back side of a ceramic tile or granite tile with good adhesive. Fix the tile (or bury it in the earth) near the entrance with the sensor assembly facing downwards. Whenever a pressure change develops near the sensor, the circuit will be activated.

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SIM STRUCTURE

ELECTRONICS MAKE A FUN

TV AND FM JAMMER 

Physical Layer of Data Communications and Computer Networks

DATA COMMUNICATIONS BASIC LEVEL

When we communicate, we are sharing information. This sharing can be local or remote. Between individuals, local communication usually occurs face to face, while remote communication takes place over distance. The term telecommunication, which includes telephony, telegraphy, and television, means communication at a distance (tele is Greek for "far").

The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data.

Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. For data communications to occur, the communicating devices must be part of a communication system made up of a combination of hardware (physical equipment) and software (programs). The effectiveness of a data communications system depends on four fundamental characteristics: delivery, accuracy, timeliness, and jitter.

1.      Delivery. The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user.

2.      Accuracy. The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.

3.      Timeliness. The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery is called real-time transmission.

4.      Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets. For example, let us assume that video packets are sent every 3D ms. If some of the packets arrive with 3D-ms delay and others with 4D-ms delay, an uneven quality in the video is the result.

Components of Data Communication

1.      Message. The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video.

2.       Sender. The sender is the device that sends the data message. It can be a computer, workstation, telephone handset, video camera, and so on.

3.       Receiver. The receiver is the device that receives the message. It can be a computer, workstation, telephone handset, television, and so on.

4.      Transmission medium. The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves.

5.      Protocol. A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating, just as a person speaking French cannot be understood by a person who speaks only Japanese.

                                                                        

A PROJECT USING A MICROCONTROLLER.

TO MAKE A MICROCONTROLLER PROJECTS YOURSELF

      THEN YOU MUST FOLLOW THESE

The following steps will help you... 

1.        

Choose a microcontroller you want to learn. Microchip's PIC series and Atmel's AVR chips are both popular choices, as well as the Arduino board. Most microcontrollers use a version of the C programming language, but there are variations. Each manufacturer also uses its own assembly language. Assembly code is less clear than C, but is more efficient because it's closer to the machine language of the chip. Because assembly language is so compact and memory on a microcontroller is limited, many programs are written in a combination of C and assembly.

Download code-editing software and a compiler for your chip. "Compiling" code transforms it from the relatively clear language you wrote it in to a language the chip can understand. Code for a microcontroller needs to be compiled for that specific chip, therefore, download the compiler from your microcontroller's manufacturer. Arduino uses its own programming language, which is similar to C, but easier to learn. Free editing and compiling software for Arduino is available on its website, along with extensive tutorials.
Read the data sheet for the microcontroller you've chosen, and find out what external circuitry you'll need to run it. You'll need a breadboard to prototype circuits on, components for the power supply circuit, a programming cable, and potentially an EEPROM memory chip for program storage. If you're using an Arduino you don't need to wire up any external circuitry before programming the chip

Set up your microcontroller on the breadboard. Follow the instructions in the data sheet for external circuits such as the power supply. Different microcontrollers require different amounts of voltage and current to run, so you need circuitry that will condition the power supply properly.

Follow the instructions you've found for your chip's programming language, either online or in a book, to write your first simple program. Don't get ahead of yourself and try something complicated. The first step is just to successfully program the chip with some simple instructions. For example, try writing a program that will blink an LED on and off. Your instructional materials will most likely have sample introductory projects as well.

Connect your microcontroller to the power supply, and connect the programming interface to your computer. Compile and download your software to test it out.

Develop your skills by adding features to your software and making it more complex. For example, try adding a dial to your blinking LED project that will allow you to change the rate at which the LED blinks.

Learn more code and become confident in your programming by working on increasingly complicated example projects, and trying out your own ideas. Don't just read the whole book through and then try something complicated. You learn programming by programming, not just reading

SMART FOOT SWITCH

SMART FOOT SWITCH 

Such jobs as jewel cutting and polishing require the workers to switch on/ off two electrical appliances one after another repeatedly for two different services Such jobs as jewel cutting and polishing require the workers to switch on/ off two electrical appliances one after another repeatedly for two different services.

Here’s a smart foot switch based on dual negative-edge triggered master slave JK flip-flop IC 74LS76 (IC1). J1 and J2 inputs are conneted to 5V through resistors R2 and R5 (each 10k), respectively. K1 and K2 inputs are grounded. Preset pins 2 and 7 are shorted and connected to 5V via resistor R7 (10k). Push-to-on switch S3 connected to the preset inputs is also grounded. Clock and clear inputs of the two flip-flops are cross-connected, i.e. CLK1 (pin 1) is conneted to CLR2 (pin 8) and CLR1 (pin 3) is connected to CLK2 ( pin 6). Clock input pins 1 and 6 are pulled up high through resistors R1 and R4 (each 4.7k), respectively.

Initially when the power supply is switched on, Q1 and Q2 outputs of the JK flip-flops are at low level (logic 0). When switch S1 is pressed for the first time, the high level (logic 1) present at J1 input is transferred to Q1 output on the trailing edge of clock (CLK1). The high level (logic 1) at Q1 activates relay RL1 through pin 16 of IC ULN2003 (IC2), turning on device 1 via its normally-opened (N/O) contacts. Clock CLK1 of flip-flop IC1(A) is also connected to clear input CLR2 of flip-flop IC1(B) so as to clear it asynchronously. Switch debounces don’t affect the circuit as the same J1 state is being transferred to Q1 output on succeeding trailing edges. At the same time, device 2 is switched off.

When switch S2 is pressed, flip-flop IC1(A) gets cleared via CLR1 and the high state of J2 input of flip-flop IC1(B) is transferred to its Q2 output on the trailing edge of clock (CLK2). This high level (logic1)  activates relay RL2 through pin 15 of IC2, turning on device 2 via its N/O contacts. At the same time, device 1 is switched off.

Now if you want to turn on both the devices simultaniously, press switch S3 momentarily. Switch S3 provides ground to preset inputs PRE1 and PRE2 of flip flops IC1(A) and IC1(B), making their Q1 and Q2 outputs high, which energises both the relays turning on the two devices. LEDs glow to indicate that both the devices are ‘on.’

Place all the three switches (S1 through S3) where you can easily press them by foot when required. The LEDs can also be mounted at a convenient location to know whether the devices are turned on.