The circuit illustrated here comes to the rescue by sniffing out defective bulbs by capacitively sensing the electric fields they produce ( see the figure ). To understand how it works, consider a string of bulbs with an opencircuited filament, labeled in the schematic as String Under Test. The intact filaments on either side of the burned-out bulb complete continuous circuits from the ac supply
Click here to download the full size of the above Circuit.
all the way around to the opposite ends of the broken filament. The ac voltage differential between wires leading to any intact bulb is zero, but the differential between the connections to the defective bulb will be the full 110 V. The presence of 110 V ac on a wire produces large electrostatic fields that are easily detected through plastic insulation. The high-impedance CMOS inputs of XOR U1 can do just that. Resistors R1 and R2, in addition to delivering operating power to the circuit, effectively suspend U1 midway between the ac supply rails. Thus, equal-amplitude (160 V p-p) but opposite-phase voltage differentials will exist between U1 and both ac rails. R4 and C1 reference U1 pin 2 to ac neutral, while R2 and the Test electrode are used to capacitively probe the voltages present in the wires of the String Under Test. U1 then performs as a phase-sensitive detector of those ac voltages. Suppose the Test electrode is held close to point A. Because A is continuous with the hot rail, the signals at U1`s inputs will have opposing phases. One input will be high (logic one) whenever the other is low (logic zero). This causes XOR U1 to hold pin 3 high, so D2 glows. If the probe is moved to points B or C, the same phase relationship will persist and D2 will still glow. But if the probe is brought near D, the sensed phase will reverse because the circuit break lies between D and the hot rail. Consequently, neutral...
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: