High & Low voltage cut-off with delay& alarm

jacky March 8, 2012 101 Comments
Description. This straight forward circuit will protect electrical appliances from over voltage as well as under voltage. The circuit also produces an alarm when the power supply comes back. An ideal circuit for home to protect your valuable equipments from voltage fluctuations. The same circuit with some modifications can be used  to make a automatic voltage stabilizer. When the mains voltage is in the normal level, the voltage at the negative terminal of zener diode D4 will be less...
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Mosquito repeller power saver

admin February 16, 2012 7 Comments
Description. Almost all liquidator type mosquito repellers are rated 5Watts. It is a pretty energy consuming game  when these repellers are operated through out the night. Even though these liquidators are switched ON and OFF in discrete intervals there will be no considerable loss in the effectiveness, and more over there will be a great saving of energy. Then why can’t we do that and that’s why I designed this circuit. The circuit is nothing but an astable multivibrator...
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Cat repeller circuit

admin February 15, 2012 5 Comments
With this cool cat/dog repeller circuit you could chase the cats  off  from any where you want. In fact, I designed this circuit to chase my cat from my computer table. Most of the animals like cats respond violently to ultrasonic sound and in fact it’s the best way to chase them off. This principle is employed in this circuit. The circuit here is nothing but an astable multivibrator wired around NE555 (IC1). The cat repellent circuit produces an...
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Infrared Motion Detector Circuit

admin August 3, 2016 255 Comments
In this tutorial, we have explained how to build a DIY (Do It Yourself) Infrared Motion Detector Circuit using 555 Timer IC, IR Diode, 2 comparator IC’s and other associated components. An Infrared Motion Detector circuit can be designed in different ways using different sort of components. This one is a low cost, easy to build one designed using inexpensive and easily available components. Note:- If you are looking for reviews of a commercial Motion Sensor/Detector to install at...
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Low cost fire alarm circuit.

admin January 21, 2014 89 Comments
Description. When there is a fire breakout in the room the temperature increases. This ultra compact and low cost fire alarm senses fire breakout based on this fact. Transistor BC177 (Q1) is used as the fire sensor here. When the temperature increases the leakage current of this transistor also increases. The circuit is designed so that when there is an increase in the leakage current of Q1, transistor Q2 will get biased. As a result when there is a...
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Rain alarm circuit

admin January 21, 2014 64 Comments
Description. Here is a simple rain alarm circuit that produces an audible alarm when ever rain falls. The rain detector circuit is based on two transistors (Q1 & Q2) and a NE555IC (IC1). The two transistors are wired as a switch which goes on when the base of Q1 is shorted to the positive of the supply by the rainwater falling on the sensor. When the transistors are ON power supply is available to the IC1 which is wired...
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USB LED Lamp Circuit

admin November 15, 2018 19 Comments
USB LED Lamp Circuit Description Here is a simple USB powered lamp that can be used to light your desktop during power failures. The circuit operates from the 5 Volt available from the USB port. The 5V from the USB port is passed through current limiting resistor R2 and transistor Q1. The base of transistor Q1 is grounded via R1 which provides a constant bias voltage for Q1 together with D2. The diode D1 prevents the reverse flow of...
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Remote controlled switch circuit

admin November 9, 2018 49 Comments
In this project, let’s build a simple Remote controlled switch for appliance controlling. If you know basic concepts of electronics, this circuit is pretty easy to build and test. The core of this circuit are two IC’s – which are infra red sensor IC’s – TSOP 1738. A couple of transistors and associated components complete the circuit – which is affordable for any hobbyist/student. Description. Here is a versatile remote controlled  switch that can ON or OFF any appliance...
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Light sensing intruder alarm

Sensitive Intruder Alarm Circuit

admin November 2, 2018 67 Comments
Super light Sensitive Intruder Alarm Circuit Intruder alarms are popular devices used in high-security areas as well as civilian houses to detect and alarm the presence of any intruders. There are different kinds of intruder detection alarms, some detect movements by using a laser, some use pressure variations etc.  Our intruder alarm works using an LDR (light dependent resistor). Also known as photoresistor its resistance varies with the intensity of light falling on it. Its resistance decreases with increase...
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DoorBell circuit using UM 66 IC

admin November 9, 2018 25 Comments
Doorbell Circuit Description Related Posts: Melody Generator using UM 66 Door Bell Circuit Using NE555   The main objective of the doorbell circuit is to convert electrical signals (input) into audio signals (output) with a single press of a switch. The circuit given below is a modified version of the Melody Generator Circuit, whose link is given above. In the previous circuit you had to keep the switch manually pressed for making the IC play the full music. Here...
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