Tag Archives: Security

555 Police siren

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The Police Siren circuit uses two 555’s to produce an up-down wailing sound. The first 555 is wired as a low-frequency oscillator to control the VOLTAGE CONTROL pin 5 of the second 555. The voltage shift on pin 5 causes the frequency of the second oscillator to rise and fall.

Drinking Water Alarm

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The State Jal Boards supply water for limited duration in a day. Time of water supply is decided by the management and the public does not know the same. In such a situation, this water alarm circuit will save the people from long wait as it will inform them as… Read more »

Mini Alarm

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Suitable for doors & windows, Portable anti-bag-snatching unit This circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand or the clothes of the person carrying the bag by means… Read more »

Powerful Security Siren

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Simple circuit – No ICs required, 12V Battery operation This circuit was requested by several correspondents. Its purpose was to obtain more power than the siren circuit already available on this website (One-IC two-tones Siren) and to avoid the use of ICs. A complementary transistor pair (Q2 & Q3) is… Read more »

Cash Box Guard

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Most thefts happen after midnight when people enter the second phase of sleep called ‘paradoxical sleep.’ Here is a smart security circuit for your cash box that thwarts the theft attempt by activating an emergency beeper. The circuit can also be used to trigger any external burglar alarm unit. The… Read more »

Laptop Protector

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Protect your valuable laptop against theft using this miniature alarm generator. Fixed in-side the laptop case, it will sound a loud alarm when someone tries to take the laptop. This highly sensitive circuit uses a homemade tilt switch to activate the alarm through tilting of the laptop case. The circuit… Read more »

Processor with Advanced Security

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Processor with Advanced Security STMicroelectronics, a global semiconductor leader serving customers across the spectrum of electronics applications, and the provider of Trusted Platform Modules (TPMs) to all major PC OEMs, has revealed the industry’s highest performing TPM enabling significantly stronger security and trust for activities like e-commerce and cloud-computing services…. Read more »

Xenon Strobe

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This is a very simple strobe circuit which I have not seen anywhere else. My inspiration came from a strobe circuit that was in a school fire alarm buzzer – the kind that has a built-in strobe light on top. Description: It’s a pretty simple circuit which some of you… Read more »

Over Voltage Protection

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Safety devices like fuses provide protection against excess current, but do nothing for transients and short duration spikes of high voltahe on the power supply lines.This circuit uses the “crowbar” method and provides fast protection against transient voltage spikes, transients that could cause damage to sensitive components. The thyristor will… Read more »