This wireless FM microphone is simple to build and it has a useful transmitting range (over 300 meters in the open air). Despite its small component count and a 3V operating voltage it will easily penetrate over three floors of an apartment building. It may be tuned anywhere in the FM band (87-108MHz) and its transmissions can be picked up on any
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standard FM receiver. The coil (L1) should be about 3mm in diameter with 5 turns 0. 61 mm copper wire. You can vary the Tx frequency by simply adjusting the spacing of the coils. The antenna should be a half or quarter wavelength long (for 100 MHz 150 cm or 75 cm). Circuit The audio amplification stage (T1) is a standard common emitter amplifier. The 47nF capacitor isolates the microphone from the base voltage of the transistor and only allows AC signals to pass. The LC tank circuit is constructed with T2, the feedback capacitor C5 and the parallel LC circuit L1, C4. The coupling capacitor(C6) directs the signal to the RF amplifier (T3). Circuit calibration: Place the transmitter about 10 feet from a FM radio. Set the radio to somewhere about 89 - 90 MHz. Spread the winding of the L1 coil apart to tune to the desired frequency.
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....
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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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