Idea of this circuit came to me at midnight when my pet dog started barking continuously on sensing a moving shadow, perhaps that of an intruder. Dogs have a night adaptation capability to maximise the sensitivity of vision in low light. They are well adapted to see moving objects rather than stationary ones in darkness. This circuit turns a lamp
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on` for a short duration when the dog barks, giving an impression that the occupants have been alerted. The condenser microphone fitted in the dog`s cage senses barking sound and generates AC signals, which pass through DC blocking capacitor C1 to the base of transistor BC549 (T1). Transistor T1 along with transistor T2 amplifies the sound signals and provides current pulses from the collector of T2. The input trigger pulse is applied to the collector of transistor T3 and coupled by capacitor C3 to the base of transistor T4 causing T4 to cut off. The collector voltage of transistor T4 forward biases transistor T3 via resistor R8. Transistor T1 conducts and capacitor C3 discharges to keep transistor T4 cut-off. Transistor T4 remains cut-off until capacitor C3 charges enough to enable it to conduct. When transistor T4 conducts, its collector voltage goes low to drive transistor T3 into cut-off state. Resistor R9 and capacitor C3 are timing components. When fully charged, capacitor C3 takes about two minutes to discharge. So when sound is produced in front of the condenser mic, TRiAC1 (BT136) fires and the bulb (B1) glows for about two minutes. Assemble the circuit on a general-purpose PCB and enclose in a plastic cabinet. Power to the circuit can be derived from a 12V, 500mA step-down transformer with rectifier and smoothing capacitor. Solder the triac ensuring sufficient spacing between the pins to avoid short circuit. Fix...
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....
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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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