Electrical Safety Tips – Ultimate Guide

jojo April 7, 2017 1 Comment
Technology and science have made homes (and workplaces) more comfortable and pleasant. People often overlook electricity as it is omnipresent to illuminate homes and operate appliances and gadgets. However, as beneficial electrical currents are to illuminate homes, workplaces, and streets, they can also cause severe injuries; and sometimes these injuries can be fatal. Injuries Due to Electrical Current The human body is a better conductor of electricity than many materials around us. Hence, if electricity does not find a...
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PIR Sensor Based Security System

john July 20, 2018 31 Comments
The circuit of an inexpensive and highly secure electronic security system is explained below. This electronic security system can be used in banks and other high security areas. A normal electronic security system will have a transmitter and a receiver. The transmitter sends out an IR laser and this will be received by the receiver. When an intruder walks past the device, the IR beam is cut and thus the alarm is activated. But, this system has some major...
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Lightning/Surge Protector Circuit Using Gas Discharge Tube (GDT)

john April 26, 2011 7 Comments
Gas Discharge Tubes (GDT) – Introduction GDT’s are special type of gas filled tubes used for wide range of electronic/electrical circuits for providing protection against lightning and other power surges.  These tubes basically has two electrodes that are kept inside a gas filled closed envelope. In case of electronic applications, the container is mostly ceramic in nature. For high grade electrical applications military tubes are used. The electrical characteristics of this tubes depends on the pressure and composition of...
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One transistor code lock

jacky March 3, 2010 19 Comments
Description. This is of course the simplest electronic code lock circuit one can make. The circuit uses one transistor, a relay and few passive components. The simplicity does not have any influence on the performance and this circuit works really fine. The circuit is nothing but a simple transistor switch with a relay at its collector as load. Five switches (S0 to S4) arranged in series with the current limiting resistor R2 is connected across the base of the...
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Wire loop alarm

jacky February 11, 2010 7 Comments
Description. Here is the circuit diagram of a very simple wire loop alarm based on  a N-channel enhancement FET 2N700, a buzzer and few passive components.In normal condition the gate of 2N700 (Q1) is connected to the ground through a 100K resistor (R2) and the wire loop. When the wire loop is broken , Q1 will be biased to ON state and the buzzer is activated.The circuit consumes very less standyby current and so the battery will last for...
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How to protect IGBT

jojo September 8, 2009 No Comments
How to protect IGBT from failures and breakdowns ? Insulated Gate Bipolar Transistors are susceptible to gate insulation damage by the electrostatic discharge of energy through the devices. When handling these devices, care should be exercised to assure that the static charge built in the handler’s body capacitance is not discharged through the device. With proper handling and application procedures, however, IGBTs are currently being extensively used in production by numerous equipment manufacturers in military, industrial and consumer applications,...
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How to protect mosfet devices

jojo September 8, 2009 15 Comments
MOSFET requires very careful handling particularly when out of circuit. In circuit a MOSFET is as rugged as any other solid-state device of similar construction and size. MOSFETs have an ultra-thin silicon dioxide layer between the channel and the gate. Because the insulating layer is so thin, it is easily destroyed by excessive gate source voltage VGS. On application of large gate voltage, an open-circuit gate may accumulate enough charge so as to develop an electric field large enough...
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How to protect Cmos devices and IC’s

jojo September 8, 2009 6 Comments
All MOS devices have insulated gates that are subject to voltage breakdown. For instance the gate oxide for Motorola CMOS devices is about 900 A thick and breaks down at a gate-source potential of about 100 V. To guard against such a breakdown from static discharge or other voltage transient, the protection networks shown in figure are used on each input to the CMOS device. Static damaged devices behave in different ways, depending on the severity of the damage. The...
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Infrared intrusion barrier

john February 28, 2010 22 Comments
Description. Here is the circuit diagram of an infrared intrusion detector. Whenever a trespasser cuts the invisible infrared beam an alarm sound will be raised. The arrangement consists of a receiver circuit and a transmitter circuit. The transmitter circuit is based on two TLC555 ICs (IC1 and IC2). The first 555 (IC1) is wired as an astable multivibrator operating at 300Hz.The second 555(IC2) is also wired as an astable multivibrator operating at 36 KHz which can be adjusted by...
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Night security light

john July 9, 2014 19 Comments
Description.  Here is a simple circuit switches on a light around 2 hours after midnight, the time at which most of the robberies taking place. This simple circuit is build around a CMOS IC 4060 to obtain the required timing. During day time the LDR has low resistance and keeps the pin 12 of the IC1 high, preventing the IC1 from oscillating. When it is dark the LDR resistance becomes high and the pin 12 of IC1 becomes low...
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