This circuit is designed to be used with the Universal Keypad Operated Switch. A few genuine mistakes - made during code entry - will not activate the device. But repeated attempts to find the correct code by trial and error - will cause the keypad to lock-up - and the Buzzer to sound. Connect the coil of a suitable relay to the Buzzer output - a
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nd you can sound a Siren instead. The circuit uses a Cmos 4017 decade counter. It counts the number of times a "Wrong" key is pressed. When the count reaches eight - it sounds the alarm and locks the keypad. The alarm will continue to sound - and the keypad will remain locked - for a period of time set by the values of C3 and R3. With the values shown - this takes about five minutes. Then the keypad becomes active once more - and the alarm is silenced. Two different control switches are provided. The first - Sw1 - simply stops the noise. Removing the lock from the keypad is left to the timer circuit. Sw1 gives you the option to silence the alarm - and still retain the keypad protection. Sw2 shortens the time it takes for C3 to charge. It both removes the lock from the keypad - and stops the noise. Any small normally-open switch will do. If you use a magnetic reed-switch - you can hide the switch within the keypad housing - and use a magnet to reset the alarm. There are three connections to be made between the Tamper-Alarm and the Keypad Circuit. Connect "Com" on the Tamper-Alarm Circuit to "Com" on the Keypad Circuit. Connect "X" on the Tamper-Alarm Circuit to Pin 1 of the 4081. And connect "Y" on the Tamper-Alarm Circuit to the junction of the relay coil and the collector of Q6. The count advances by one every time a "Wrong" key is pressed. A wrong key is any key that takes pin 1 of the 4081 low. Since "E" takes pin 1 low...
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....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
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....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
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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