This circuit features automatic Exit and Entry delays - timed bell cut-off - and system reset. It has provision for normally-open and normally-closed switches - and will suit all of the usual input devices (Pressure Mats, Magnetic Reed contacts, Foil Tape, PIRs and Inertia-Sensors). If the green LED is not lighting - check for an open window or do
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or etc. Once you`re satisfied that the building is secure - and the green LED is lighting - move SW1 to the "set" position. At this point - the red LED will light - and the Exit Delay will begin. The length of the Exit Delay is set by the value of R12. With a 220k resistor - you have about 30 to 40 seconds to leave the building. As you do so - the Buzzer will sound. It should stop sounding when you close the door behind you. This indicates that the trigger circuit has been successfully restored within the time allowed. When you return to the building and open the door - the Buzzer will sound - and the Entry Delay will begin. The length of the Entry Delay is set by the value of R8. With a 470k resistor- you`ll have about 30 to 40 seconds to move SW1 to the "off" position. If you fail to do so - the Siren will sound. The length of time the Siren sounds is set by R11. With a 4M7 resistor it will sound for about 15 to 20 minutes. Then the relay will drop out - and the alarm will attempt to reset itself. It does this by using Q3 to switch itself "off" briefly. If the trigger circuit has been restored - the alarm will reset. If not - the attempt will fail - and the alarm will reactivate. It will go on trying to reset itself every 15 to 20 minutes - until either the trigger circuit is restored - or the alarm is switched off. All the usual triggering devices may be connected to the input terminals. These include Inertia-Sensors....
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
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The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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