Use this in your garden and listen for any unusual sounds, or maybe just wildlife noises. If you have a car parked in a remote location, the microphone will also pick up any sounds od activity in this area. The cable may be visible or hidden, screened cable is not necessary and you can use bellwire or speaker cable if desired. Starting from the right
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hand side, the power supply. I have used 12V as a standard power supply voltage, or a 12V car battery may be used. The circuit is in two halves, a remote microphone preamp, and an audio amplifier based around the National Semiconductor LM386 audio amplifier. The remote preamp uses an ECM microphone to monitor sound. A direct coupled 2 stage amplifier built around Q1 and Q2 amplify the weak microphone signal. Preset resistor R2 acts as a gain control, and C1 provides some high frequency roll off to the overall audio response. Q1 is run at a low collector current for a high signal to noise ratio, whilst Q2 collector is biased to around half the supply voltage for maximum dynamic range. The power supply for this preamp is fed via R10 and R6 from the 12V supply. C4 ensures that the preamp power supply is decoupled and no ac voltages are present on the power lines. The amplified audio output from Q2 collector is fed onto the supply lines via C6 a 220u capacitor. The output impedance of Q2 is low, hence the relatively high value of C6. C6 also has a second purpose of letting the output audio signals pass, whilst blocking the dc voltage of the power supply. At the opposite end, C7 a 10u capacitor, brings home the amplified audio to the listening location. The signal is first further amplifier by a x10 voltage gain amplified using the TL071. C8, a 22p capacitor again rolls off some high frequency response above 100kHz. This is...
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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