This is a universal four-digit keypad-operated switch - with a difference. Instead of entering the security code one number at a time - the four keypad buttons must be pressed simultaneously. In other words - the four numbers must be entered in parallel. The intruder won`t know the code. He won`t even know how many digits there are in the code. An
Click here to download the full size of the above Circuit.
d he almost certainly won`t know that the entire code must be entered simultaneously. Added to this - is the extra layer of security provided by the secret time-lock. After a few incorrect codes are entered - the circuit will stop responding to the keypad. And any further attempts to crack the code - will be unsuccessful. If you don`t want the time-lock feature - leave out D6, C6, R8 & R9. And connect pins 8 & 9 of the IC together. If you want to use a three-digit security code - leave out D4, C4 & R4. And connect pins 5 & 6 of the IC together. Three digits are easier to enter than four. Do not use the "on-board" relay to switch mains voltage. The board`s layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount a suitably rated relay - somewhere safe - Away From The Board. Choose the four keys you want to use for your code - and connect them to "A B C & D". Since the keys have to be pressed simultaneously - the order in which you make the connections is irrelevant. Wire the keypad`s common terminal to "Com". And connect all the remaining keys to ground. That is - to "E". The circuit will power-up with the relay energized. When you press keys "A B C & D" simultaneously - the relay will de-energize. To energize it again - press any key not included in your code. That is - any key connected to "E". If you want to reverse the action of the...
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.....
characters left: