Alarm Circuits
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Fire Alarm Circuit using LDR (Light Depending Resistor) as ablaze sensor. It warns the user adjoin blaze accidents. It relies on the smoke that is produced in the accident of a fire. Back this smoke passes amid a LED and an LDR, the bulk of ablaze falling on.... -
Rain Alarm. This circuit gives out an alarm when its sensor is wetted by water. A 555 astable multivibrator is used... -
Motorcycle Alarm Number 4. This is a simple - easy to build - transistor based motorcycle alarm. It`s designed to work at 12-volts. But - if you change the relay for one... -
after SCL is high at hand must be refusal chande voguish SDA line lone followed by the data is legally binding, the data loose change be supposed to be there made only as SCL is low. taking into account transfer of lone byte of data the reciever has to.... -
This Photodiode based Alarm can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered. The.... -
This is a car alarm simulator which using the LED as a simulation output. This simple circuit can tell you whether your car is running or not by detecting the voltage difference when the car is on and off. This occurs because when your car is running the.... -
Whenever AC mains supply fails, this circuit alerts you by sounding an alarm. It also provides a backup light to help you find your way to the torch or the generator key in the dark. The circuit is powered directly by a 9V PP3/6F22 compact battery. Pressing.... -
The danger always exists, when the fuel gases such as propane or gas are confined to a small area. The alarm of toxic gases figs. 1-45 utilizes a tin-oxide-semiconductor. A coil of thin wire heated by a battery 12 V via IC1 and IC2, which pulses the voltage.... -
This circuit sent out an alarm when its LDR sensor is exposed to light by sun or lamp. A 555 astable multivibrator was used here which sent signal a tone of about 1kHz upon detecting light. The sensor when exposed by light completes the circuit and makes the.... -
This is a simple proximity switches with IC 4049th The IC4049 is a bipolar monolithic integrated circuit for use in metal-detection system / proximity sensing applications IC4049 includes an oscillator constituted by an external parallel resonant tank.... -
The system of using this circuit is positioning a little magnet close to the stalk switch SW1 while being connected to the hand or garments of the individual holding the sack with the use of a tiny cable. Since the circuit is tiny, it can be put in a tiny.... -
When the light falls on the LDR, it becomes low ohmic. The voltage at the junction of LDR/R2 charges the C2 via the R1 slowly. After about 10 seconds, the capacitor voltage reaches the input threshold of U1. Then U1 generates a square wave signal with a.... -
The original smoke alarm circuit has some problems and has left some hobbyists and students disappointed. Rather than to attempt to solve its many problems, I have created an update that uses the venerable LM741 op amp. It is simpler, more conventional,.... -
This is a two-zone alarm - with automatic exit, entry and siren cut-off timers. It can be triggered by the usual types of normally-closed input devices - such as magnetic reed contacts - foil tape - PIRs etc. I`ve used a 12-volt supply in the diagram - but.... -
The brake lights of the automobile trigger this circuit on and off. This save the annoyance of the alarm when it is not needed. This is an older circuit which was published in Popular Electronics Magazine, but still a good circuit today... -
The CD4001 quad 2-input NOR gate is a very versatile IC that can be used in an almost infinite variation. Here we will use it in the application of a simple alarm system. The power supply suggested for the CD4001 is 5 to 15Vdc Max. The CD4001 has a typical.... -
There are a lot of alarm systems on the market but you might be inclined to build your own. This little project can be put together using inexpensive parts readily available. The alarm transmitter module allows for a delayed trigger and auto turn-off as it.... -
At present, it is numerous to adopt the telephone line as long-range control and alarm system of the transmission medium, associated too more research [1, 2 ]. This kind of system is generally made up of alarm device and calling the police to accept the.... -
With the quickening of the modern rhythm of life, the frequency happening in traffic accident is increasing too, in order to improve the safety that the car runs, this text introduces the mechanically controlled car anticollision alarm system of a one piece..... -
Take precautions against the coefficient is low, the safety is bad, the applicable space is smaller and smaller. With the development of science and technology, people develop already the intersection of door and magnetic, touch-type, the intersection of.... -
This infrared alarm barrier can be used to detect persons passing through doorways, corridors and small gates. The transmitter emits a beam of infrared light which is invisible to the human eye. The buzzer at the output of the receiver is activated when the.... -
The frequency is controlled by the pin 5 of the IC. When the supply is switched ON, the capacitor charges slowly and this alters the voltage at pin 5 of the IC hence the frequenct gradually increases. After the capacitor is fully charged, the frequency no.... -
Over-Temperature Alarm Circuit Uses Common, Inexpensive Components | Negative-temperature-coefficient (NTC) thermistor, ICs... -
A common piezoelectric alarm, such as the Murata (Smyrna, GA) PKB5-3A shown, has many valuable attributes. It is compact, lightweight, efficient and reliable. However, the loud, high-pitched sound output can be quite irritating in many applications. The.... -
This circuit detects when a tube is empty and pulses a piezo buzzer in. 5 second intervals. I have it working with 5v on a breadboard, but I need to move it to 12v from a wall wart. Secondly, with 12v R1 should be 220 1W, but I want to stick with 1/4W.... -
This Dummy Alarm project makes an LED flash briefly once every 5 seconds to imitate the indicator light of a real alarm. The circuit is designed to use very little current to prolong battery life so that it can be left on permanently. An on/off switch is not.... -
The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery.... -
The circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and.... -
Device such as burglar alarms and sirens, whose basic purpose is to monitor tested circuit diagram with description of burglar alarm alarm using dual operational amplifier... -
Digital Mains Failure / Resumption Alarm use optocoupler and produce sound.circuit diagram with description of digital mains failure various alarm cirucit... -
Many fire alarm circuit is published in different website. But, here in this website is a simple and inexpensive project of fire alarm using thermistor. where thermistor is used astemperaturesensor of fire alarm. Working principle of thermistor is same as....
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This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of.... -
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is.... -
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to.... -
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This.... -
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the.... -
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,.... -
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the.... -
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power.... -
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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