simple security alarm
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Key Code Combination High Security Door Lock
This project involves an electronic lock that supports numerous combinations, which can be easily modified. It unlocks only with the correct sequence of four consecutive numbers. A significant feature of this electronic lock is that the four numbers must be...
Alarm Sounder For Flex Switch Circuit
This is a cross-sectional diagram of a flex switch. They can be used as pushbuttons or even position sensors. This schematic diagram shows an oscillator, which is used as an alarm sounder, triggered by a flex switch.
The flex switch is...
Power Buzzer
A powerful buzzer in the room, combined with a pushbutton at the bottom of the stairs or in the kitchen, could be very useful in such situations. The core of this circuit is formed by IC1, a TDA2030. This integrated...
Automatic Turn-Off Alarm With Delay
In this circuit, IC1A and IC1B serve as a monostable multivibrator. Any input from the sensors SI through S5 triggers IC1A to produce a logic low signal, which activates IC1B, turning on Q1 until the capacitor C3 discharges through resistor...
Novel Buzzer
This novel buzzer circuit uses a relay in series with a small audio transformer and speaker. When the switch is pressed, the relay will operate via the transformer primary and closed relay contact. As soon as the relay operates the...
Add a sensor to a board and measure something with it
This week's plan is to build a device that warns of the potential for a knockdown, which is the process by which an over-canvassed ship is laid over on her beam-ends. The risk of sinking is high during this event,...
Power disconnection alarm circuit diagram
The circuit operation principle of the device illustrated in Figure 13 is as follows: When the barbed wire (Fe) remains intact, the output pin (O) of the LSE is at a high state. Consequently, the transistor (VT) remains off, and...
Mini Alarms
This is a selection of small self-contained alarm circuits. They have a very low standby current; and are suitable for battery operation.
The described alarm circuits are compact and designed for low power consumption, making them ideal for battery-powered applications. These...
buzzer set
Building a competition buzzer set involves the construction of a contest buzzer system. The kit includes an etched, undrilled printed circuit board, a programmed PLD, a 556 timer, various mounting hardware, and a detailed assembly manual. The kit is priced...