Rongge

Hello Freinds ! Here designed SIMPLE BAR DISPLAY WITH ALARM FLASHER . Schematic: Return to Display Circuits. By using two switching transistors and two LEDs, this circuit can distinguish low-level ac and dc signals. If the red LED illuminates, the signal is positive dc. If the yellow LED lights, the signal is negative dc. If the signal is ac, both LEDs will light. Bar Display With Alarm Flasher Circuit Schematic

A very simple heat detector alarm electronic project can be designed using the UM3561 sound generator circuit and some other common electronic parts . This heat detector electronic circuit project uses a complementary pair comprising npn and pnp transistor to detect heat . Collector of T1 transistor is connected to the base of the T2 transistor , while the collector of T2 transistor is connected to RL1 relay . T3 and T4 transistors connected in darlington configuration are used to amplify the audio signal from the UM3561 ic . Heat Detector Alarm Circuit diagram When the temperature close to the T1 transistor is hot , the resistance to the emitter –collector goes low and it starts conducting . In same time T2 transistor conducts , because its base is connected to the collector of T1 transistor and the RL1 relay energized and switches on the siren which produce a fire engine alarm sound . This electronic circuit project must be powered from a 6 volts DC power supply , but the UM3561 IC i...

Are you having a hard time waking your hubby from sleeping? And when you leave the house for work, are you in doubt that he has not gotten out of bed? One thing that will stop your worries is to use this clock that does not just tell time but also “swears”. This is an All-in-one alarm clock. It shows an alphanumeric character, it has a calendar, temperature, and a light sensor to control its brightness. You can plug it on to your power source or use a battery. Although this is cool, It’s not ok being around kids. We don’t want young kids to learn to swear or say bad things, right?   Streampowers

Circuit Diagram Description An reverse biased germanium diode is used here as a heat sensor at normal room temperature the reverse resistance of the diode is very high in the order of over 10 kilo ohms so it produce no effects on the transistor Q1 which conducts and keeps the reset pin 4 of ic 555 at its ground level, and so the alarm doesn’t get activated. When the temperature in the vicinity of the diode (the sensor) increases in case of fire, the reverse resistance of the germanium diode drops at about 70 degree its resistance drops to a value below 1 kilo ohms this stops Q1 conduction and the 555 ic pin 4 becomes positive through the resistor R1 which activates the alarm. Note: For installation of the alarm two or three reverse biased germanium diode can be connected in parallel at different locations in case of fire any of the diode can sense the heat and can activate the alarm. DR25 Germanium diode is recommended for use but still it can be replaced with base emitter junctions o...

Here is an interesting circuit , it is used to make a kind of lock or locks for bicycles , it allows owners to implement a bicycle lock and electronic alarm with a low cost . The operation of the electronic lock is simple , it has a circuit that uses a tone generator IC UM3561 , this IC generates a sound when your bike has the protection wire that surrounds the wheel broken .   Blocking Circuit with Alarm for Bicycle Circuit Diagram Click here to download complete project

Here is simple alarm circuit project of Theft Preventer Alarm using NE 555 circuit. This circuit utilising a 555 timer IC can be used as an alarm system to prevent the theft of your luggage, burglars breaking into your house etc. The alarms goes ON when a thin wire, usually as thin as a hair is broken. Theft Preventer Alarm Circuit Diagram: The circuit is straightforward. It uses a 555 IC wired as an astable multivibrator to produce a tone of frequency of about 1kHz which gives out a shrill noise to scare away the burglar. The wire used to set off the alarm can be made of a thin copper wire like SWG 36 or higher. You can even use single strands of copper form a power cable. The circuit operates on a wide range of voltages from 5V to 15V. The speaker and the circuit could be housed inside a tin can with holes drilled on the speaker side for the sound to come out.

We usually lock our luggage utilizing a chain-and-lock arrangement when in travelling by a train of bus. But, still we are worried, apprehending that someone may possibly break the chain and steal our luggage. The following schematic is really a very simple and easy build luggage security alarm circuit to alert you when a person tries to break the chain. Transistor T1 allows supply to the sound generator chip when the base current begins flowing through it. When the wire (thin enameled copper wire of 30 to 40 SWG, applied for winding transformers) loop around the chain is cracked by someone, the base of transistor T1, which was previously linked with positive rail, becomes opened. Because of this, transistor T1 gets forward biased to extend the positive power source towards the alarm circuit.   In idle mode, the power source consumption within the circuit is lowest and as a result, it could possibly be utilized for numerous travel hrs. To make it possible for generation of various ...

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.   Photodiode Alarm Circuit Diagram   The circuit uses a PN Photodiode in the reverse bias mode to detect light intensity. In the presence of Laser / IR rays, the Photodiode conducts and provides base bias to T1. The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential. IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable operates only when its resent pin becomes high. When the Laser / IR beam breaks, current thorough the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated. IR Transmitter Circuit   A simple IR transmitter circuit is given w...

This is a very simple Electronic Circuit Project of piezo alarm circuit. Piezo alarm which will generate a sound around 110dB can be designed using this diagram. This Piezo alarm siren circuit diagram use some common components like 555 timer ic, you can use two 555 timer circuits or one 556 circuit. Electronic Alarm Project of Piezo with 555 Timer Circuit Diagram: This Piezo alarm siren circuit project use two piezo sounders with high efficiency and can be powered from a wide input voltage, between 5 and 15 volts. This circuit is very easy to build, maybe you will have a little trouble with the T1 and T2 auto-transformers. Both auto-transformers used in this project are the same type and require between pin 1and 2 1500 turns of 44 SWG wire and 220 turns between 2 an 3 using 40 SWgG wire. In this circuit the IC1:B closest to the piezo elements is set to oscillate around their resonant frequency. The frequency is then varied via input pin 11 from the other 555, IC1:A. This modulating in...

GIVES BEEP WHEN WATER IS IN CONTACT WITH THE WIRE Water is a conductor of electricity. When water is in contact with the probe then there is a flow of current which reaches to the base of Q1. Transistor Q1 is a NPN transistor which conducts. With the conduction of Q1 electron reaches to Q2 which is a PNP transistor .Q2 also conducts and current flows through the speaker. In a speaker there is inductive coil which causes motion in one direction and also produce induce current which is in opposite direction to the flow of current this induce current in the form of pulse flows through a capacitor, resistance and switches off Q1 and relax .this process repeats again and again till probe is in contact with water or we can say there is a oscillation in the circuit thus speaker diaphragm vibrates and gives a tone. Frequency of the circuit depends on the value of Speaker Coil impendence, Capacitor and Resistance Value. Sourced By : Streampowers

Even the best car alarm is useless if you forget to set it upon leaving your car, whence this circuit. The relay has a make and a break contact: the  former is necessary to delay the switching in of the  alarm after you have got out of your car, and the  latter serves to switch on the car alarm proper. Immediately on re-entering your car, you must press the hidden switch, Si. This causes silicon-controlled rectifier Thi to conduct so that the relay is energized. At the same time, the green LED lights to indicate that the alarm is switched off.   Circuit diagram :   Best Automatic Car Alarm Circuit Diagram As soon as the ignition is switched off, T, is off, T2  is on, and the buzzer sounds. At the same time,  monostable IC1 is triggered, which causes T3 to  conduct and the red LED to light. The silicon- controlled rectifier is then off, and D4 is reverse  biased, but the relay remains energized via its make  contact for a short time...

This circuit alarms you whenever their is a power failure in your mains supply and the circuit doesn't use any additional Voltage Source. It is simple to design and effective to construct. Power failure alarm circuit monitor your supply line and trigger the buzzer to produce beep sound when their is a Voltage drop. This circuit finds applications in Refrigerators, Fish Tank, air conditioner etc... All the components used in this circuit is cheap to buy and easily Available in the market. CIRCUIT DIAGRAM FOR SIMPLE POWER FAILURE ALARM COMPONENTS AND THEIR SPECIFICATION FOR POWER SUPPLY FAILURE ALARM CIRCUIT WORKING OF SIMPLE POWER FAILURE ALARM CIRCUIT The circuit mainly consisting of a stepdown Transformer, a bridge rectifier, an PNP transistor and a buzzer. The stepdown Transformer step-down the high Voltage AC to a safer value for the circuit to work fine. And this low Voltage alternating Current is now fed to a Bridge rectifier to make it unidirectional. The diode D2 and Capacit...

To open the lock, buttons S1, S2, S3, and S4 must be pressed in this order. They must be pressed for more than 0.7 seconds and less than 1.3 seconds. Alarm Using 4-Buttons Circuit Diagram Reset button S5 and disable button S6 are also included with the other buttons and if the disable button is pressed, the circuit will not accept any code for 60 seconds. Each of the 3v3 zeners can be replaced with two red LEDs and this will show how you are progressing through the code. Make sure the LEDs are not visible to other users.