This unit is designed for monitoring the audio output level across a loudspeaker when carrying out alignment of radios. As no great precision is required, a simple passive circuit arrangement has been used. The circuit is a voltage-doubling rectifier driving a panel meter. The input signal is AC coupled via C1. D1 holds the signal so that the nega
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tive peaks are at ground potential. The mean level is above ground, so the polarity of C1 is important. The peak level is rectified by D2 and stored in reservoir capacitor C2. The value of R1 has been selected to give the required calibration with a 250uA meter movement. If a 100uA is used, the alternative component values should be used. The prototype was constructed using a small piece of plain matrix board. Tag strip or stripboard could be used if preferred. A PCB would be overkill for such a simple design! The meter used on the prototype was a low cost ( £3. 20) 250uA signal strength meter obtained from Maplin (Order Code LB80B). This is marked "SIGNAL" and has an arbitrary scale marked 0 to 5, making it ideal for the purpose. A higher quality meter could be used, but this would offer no real advantage. The input may be bought in via a length of two-core speaker cable. The free end may be fitted with a pair of small crocodile clips for easy connection to the speaker tags in the radio being aligned. The unit is designed for connection across a loudspeaker. If you wish to disconnect the loudspeaker because of the annoying noise, replace it with a suitable wirewound resistor. Two people have contacted me regarding the availability of the OA47 germanium diodes. These are listed in the current Maplin catalogue (Order Code QH70M, price 49p each). I followed your online article using 10uF for C1, 2. 2uF for C2, silicon diodes...
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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