The circuit described here was designed as an addition to a remotely controlled garage door opener. The problem was that a brief burst of interference, arising from a thunderstorm or a mains spike, was enough to trigger the mechanism, and the author found this a nuisance. The effect of the circuit is to enable the output from the receiver module o
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nly when a relatively long pulse (more than about 0. 5 s) is received. The circuit can of course also be used in other similar situations, such as electrically-powered shutters, alarms and the like. At the heart of the circuit is NAND gate IC1. C. The output of the circuit (after inverter IC1. D) only goes high when both inputs to IC1. C are at a high level. When the circuit is triggered T1 conducts, and the output of inverter IC1. A, and hence also pin 8 of IC1. C, go high. If we now arrange things so that for a preset time the other input to IC1. C remains low, the trigger signal will not be propagated to the out-put until this period has elapsed. In the case of the author`s garage door opener, this will only happen if the button on the transmitter is held down. The 555 timer is used to generate the delayed gating signal for IC1. C. It is wired as a monostable multivibrator in a similar fashion to the arrangement in the Economy Timer` circuit elsewhere in this issue. When the circuit is triggered T2 will briefly conduct as a result of the positive edge at the output of IC1. A. This triggers the 555 timer: its out-put will go high, and thus pin 9 of IC1. C will go low. Because of the propagation delays through the components a very short low pulse will appear at the output of IC1. C when the circuit is triggered. The RC combination at the input to IC1. D ensures that this does not affect the output. When the period of...
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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