The operating systems like Archlinux ARM, OpenELEC, Pidora, Raspbmc, RISC OS and the Raspbian and also Ubuntu versions are available for the Raspberrypi board. Linux operating systems especially Ubuntu is preferred for all kind of programming and development. The immediate advantage of having an Operating System like Ubuntu running on an embedded system device is multitasking. The Raspberrypi is a board actually designed for helping computer education for remote schools but it is a nice platform for programmers especially beginners to explore various coding techniques. In a multi-tasking system several processes will be running at a time. The Operating System can control a process by sending signals to it. A user can sometimes initiate a signal sending and the processes can also send signals to each other. This project demonstrates how a process can receive the signal called SIGALRM from the OS and use it.
Many a time it happens we forget to switch off the gas, electric oven, stove or motor while watching TV or taking on the phone or while talking to a friend in your neighborhood. To solve this problem we have described a circuit below which alarms you after the preset time interval. It will give a loud musical alarm and reminds you that you to off your machine or gas. It uses NE555 which is a well known multi-vibrator IC.Here 555 timer IC is wired as an a-stable oscillator which provide a clock pulse to CD4017 IC. CD4017 which is a medium speed Johnson Counter that works at 10MHz and has 10 decoded outputs. CD4017 ICs are widely used in frequency dividers, binary counters, and divide by N counters and register design applications.
The circuit described below produces a musical sound whenever you put your hand on the sensor or a shadow of the person falls on sensor. It can be named as shadow alarm. This circuit can be used at our homes near door bell. Whenever somebody is present on the door it alerts us about the presence even before the door bell is pressed. A very useful technique in restricted area where only authorized person are allowed but in that case sensors need to correctly chosen. This circuit can also used to switch ON the light when darkness is detected with little modification. For example you can connect relay at output(in place of UM66 IC) to on the bulb or you can use LED’s in series. So when there is no light this can be our emergency torch. It can serve the decoration purpose, by switching the light ON when the darknessis detected at night.This can be done by connecting LED’s at output.This circuit can operated with pencil cell as it require less only 3V for its operation.Can easily be mounted because of less components used in circuit.
In homes considerable amount of water lost every day due to refilling of water tank. We can avoid this just by having little knowledge with electronics. Here [[wysiwyg_imageupload::]]I have described a simple circuit with the help of two IC that is LM741 and UM66 which will give an musical alarm when your tank become full so that you can avoid wastage of water due to over flow.In this circuit IC LM 741 is an operational amplifier which is working as a comparator to sense the level of water present. And IC UM66 is used as melody generator. When tank is empty, water will not touch metal plate or sensor in that case inverting pin of LM741 IC is at higher potential in comparison to non inverting pin of IC1. Keep on reading to know more.
This small alarm circuit protects your valuables from thefts by engaging the alarm when somebody attempts to pick up your suitcase.It can be operated with the [[wysiwyg_imageupload::]]help of 3V therefore power consumption is also very less.It uses very less components that why it can be easily fit on the suitcase. Due to its small size you can easily carry this small alarm while you are travelling.The circuit is build around IC LM358 which is a low power transducer amplifier. The important component of this circuit is piezo sensor. Piezo sensor converts vibration or pressure into electrical signal. This same piezo element can be found inside the buzzer or you can purchase the same from market. Its working is somewhat similar to capacitors. Piezo element holds the charge when potential applied, until it is mechanically disturbed or some vibration will be there.
The circuit is built around two IC namely CD4060 and UM66 with few more components. IC CD4060 is 14 stage ripple carry binary counter, divider and an oscillator. Its built in oscillator is main feature of this IC that’s why it can be used in numerous application like flasher, clock generator in timer circuits. UM66…
This switch, when hidden under the floor mat, triggers an alarm when the person walks over it. Mat switch can be used as a security measure in a restricted area. [[wysiwyg_imageupload::]]Just put the switches beneath the mat after regular intervals so that when anybody who puts his feet on switch will engage the alarm.This circuit is built around the CMOS UM3561 IC which is mostly used in toys and alarms because of its low cost and power saving ability.One of the advantages of this switch is that the circuit does not consume the battery current in standby mode therefore lead to longer battery life. Also, you can also stabilize 9V DC mains adaptor in place of the battery. Read more to find out how the circuit is designed and how it works.
While travelling in public transport such as buses or trains, people usually carry expensive belongings and are quite insecure about their safety. Even though after [[wysiwyg_imageupload::]]locking the luggage thoroughly, there is always a worry about it.To solve this problem here is a simple circuit based on NAND gate. When somebody tries to steal the luggage, the circuit will give a warning alarm. An audio visual indication can also be provided by connecting it to the relay.This project circuit can also be used in home to prevent the attempt of burglary as when somebody tries to open the door, the loop breaks and the alarm. The project is built around CD4011 with components like LDR, variable resistor, capacitor, transistor and relay.. It generates a warning beep when somebody attempts to open the locker.
The project presented can be used as a smart circuit for the cash box that thwarts any theft attempt by activating an emergency alarm. This can also be used to [[wysiwyg_imageupload::]]trigger any external burglar alarm by connecting a relay to the output of the circuit. The circuit is built around a NAND gate IC in which all gates are used as an inverter. The circuit is based on the concept of Light Dependant Register (LDR) whose resistance varies with the intensity of light falling on it. This small circuit can also be installed in a locker system where if somebody tries to open the locker, the light will fall on the LDR and the circuit will start sounding with the help of buzzer connected to the relay. A switch is also provided so that the circuit can be switched off when not in use to save the battery power.
It is very essential to keep the door of fridge closed all the time. The refrigerator will not work efficiently if the door is left open. To avoid such situations, this [[wysiwyg_imageupload::]]project presents an interesting circuit that will sound an alarm if the door is not properly closed This alarm circuit will not buzz till the door is opened and closed between the predefined times but if it crosses the predefined time it will start buzzing. NAND Gate is created by applying NOT operation to an AND gate. Hence, the outputs of this gate are opposite to that of AND gate when the inputs are kept same. This simple circuit project is based around transistor, switches and NAND gates. In the standby mode, the switch is closed and the current flowing through R1 is grounded through the switch.
The circuit gives an audio visual alarm when somebody enters from a door. This project can also be used in locker and almirah door. This circuit is based on [[wysiwyg_imageupload::]]operational amplifier LM741 and LDR. An op-amp produces an output voltage that is hundreds of thousands times larger than the voltage difference between its input terminals. The circuit comprises of Operational amplifier A741 which is used as sensitive voltage comparator, LDR and Preset VR1. The preset provides reference voltage to the non-inverting terminal pin 3 and LDR. R2 is connected to inverting pin 2 of IC1. How does the alarm sense someone entering? How is the circuit constructed? What is the role of op-amp in its working? Continue reading to find out how answers to these questions and more.
BACKGROUND One day at the evening time I was talking with my uncle on telephone. He asked me some question base on my learning means what are you learning? which type of engineering are you doing? He ask me that have you made something new during your engineering? That time I don’t have any answer. But…
This project presents another application of RF (radio frequency) communication. The capability of fire alarm circuit can be improved by incorporating an RF [[wysiwyg_imageupload::]]module. This way the temperature sensor and buzzer for alarm can be placed away from each other. This provides flexibility in installing various sensors at different locations in a building and thus overheating at a place (due to fire) would signal the buzzer to go on. This project about fire alarm circuit can be divided into four parts, namely, temperature sensor, comparator, transceiver part (RF module) and the output. In this circuit a temperature sensor (LM35) is placed at a certain place and its output is given to the negative end of a comparator. LM324 has been provided in the circuit for comparator. The positive end of comparator is connected to a preset, to set the reference temperature. As long as the output of temperature sensor is below the set reference, the output of comparator stays high.
This project extends the functionality of intruder alarm to alert a user at a distant location. The intrusion can be detected at a faraway place by making use of RF [[wysiwyg_imageupload::]]communication. For this purpose, an RF module can be used as has been explained here. This project about intruder alarm circuit can be divided into three parts, namely, IR circuit, transceiver part and the output. The IR circuit is used as a sensor to detect an intrusion in its proximity. RF module works as the transceiver here. For more details, refer wireless RF remote. The transceiver transmits the signal generated by IR sensor. It provides this signal to the data pin of decoder IC. The output part consists of a NOT gate IC 74LS04 (to invert the low signal) and a buzzer to alert the user. Read more to find out how the circuit is constructed and how it works.
Celsius scale thermometer displays the ambient temperature through a LCD display. It consists of two sections. One is that which senses the temperature. This is a temperature sensor LM 35. The other section converts the temperature value into a suitable number in Celsius scale which is done by the ADC0804. A digital thermometer can be easily made by interfacing…
Shadow alarms are widely used for security purposes. A shadow alarm is a device that generates an alarm whenever a shadow falls on it. This project can be easily [[wysiwyg_imageupload::]]installed on the windows and doors. This circuit demonstrates the principle and operation of a simple shadow alarm using LDR. Other than the LDR, the circuit consists of LEDs for input and output purposes, buzzer and a LM324 comparator IC. Keep on reading to find out how the circuit is constructed and how it can be made to work.
This electronic device is designed to alert the user to an intrusion. The project consists of a sensor and a control unit which are connected to each other. The [[wysiwyg_imageupload::]]sensor detects the interruption whenever an object or person comes between its transmitter and receiver. This interruption results in a signal generation which is supplied to a speaker. This way whenever an intrusion takes place, the speaker goes on. Such devices are installed at various locations in houses or offices, especially near doors, windows.In this project, the transmitter part of the circuit is an Infrared (IR) Led which transmits continuous IR rays to be received by IR receiver. The reception of rays at IR receiver results in high voltage at the output. The output of this IR sensor remains low when no signal is received. Keep on reading to find out how the circuit is constructed and what makes it work.
At times we forget to switch off our heating devices and eventually they get damaged. Therefore there is always a need of a device which can alert by sounding [[wysiwyg_imageupload::]]an alarm if the device temperature goes beyond a particular value. Same concept can be used in this project about fire alarm. If a building catches fire then it will raise an alarm and people could evacuate the building. This circuit uses a LM35 temperature sensor along with a LM339 comparator. Interfaced to LM339 are the following components: Resistors, Capacitors, Transistors, 555 Timer, Buzzer (output). This project about fire alarm circuit is based around LM35 which is a temperature sensor and could be used to switch an alarm when temperature goes beyond a preset value. In this circuit the output of LM35 is fed to the negative pin of comparator of LM339. The positive input is connected to a preset VR1 of value 10K.
Sometimes there is need of devices which should intimate us when power goes off, so that we could switch off our devices if they are battery [[wysiwyg_imageupload::]]operated or they are getting power from some other limited source [such as for computer using UPS(uninterrupted power supply)]. This project can solve our purpose and can intimate us if power supply fails. This circuit has a 555 timer at its heart and following components that aid its working:1N4148 Diodes Resistors in the range of Kilo and Mega Ohms. Capacitors at the range of Micro Farads and Nano Farads.A 9volt battery taking care of the power supply of the circuit.
This article illustrates the construction and working of a liquid level indicator. Such an indicator is used in tanks to indicate the level of liquids and alert us when [[wysiwyg_imageupload::]]the tank is full. So by this circuit we can monitor the various levels of the tank and can avoid spillage of water and also we can configure our supplies according to the various levels of tank. Such module or circuit can be installed in big buildings where manual monitor of tanks is difficult and its indicator can be placed at some centralised place. Initially when the tank is empty LCD will show the message VACANT. As the tank starts filling up wire at different levels get some positive voltage, due to conducting nature of water. This voltage is then fed to their corresponding pins on controller. When level reaches to quarter level, LCD displays the messageQUARTER. On further rise of level, HALF and 3/4 QUARTER are displayed on LCD.