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This circuit generates a two-tone effect very much alike the cuckoo song. It can be used for door-bells or other purposes thanks to a built-in audio amplifier and loudspeaker. Used as a sound effect generator it can be connected to external amplifiers, tape recorders etc. In this case, the built-in audio amplifier and loudspeaker may be omitted and the output taken across C8 and ground. There are two options: free running, when SW1 is left open, and one-shot, when SW1 is closed. In this case a two-tone cuckoo song will be generated at each P1 pressing. Cuckoo Sound Generator Circuit diagram: Parts: R1,R5___________1K 1/4W Resistors R2_____________50K 1/2W Trimmer Cermet R3______________8K2 1/4W Resistor R4_____________82K 1/4W Resistor R6______________1M 1/4W Resistor R7,R17,R20,R21_22K 1/4W Resistors R8,R10,R11,R19_10K 1/4W Resistors R9____________150K 1/4W Resistor R12_____________4K7 1/4W Resistor R13___________100K 1/4W Resistor R14___________220R 1/4W Resistor R15,R22________20K 1...

This electroinc Circuit Project of  Mobile phone detector circuit can sense the presence of an activated mobile cell phone from a distance of one and-a-half meters. If a RF signal is detected the cell phone detector circuit will inform you using a sound alarm (beep sound ) and a blinking LED . In this type of circuit (that use high frequency 0.9-3Ghz ) you can not use an LC circuit for frequency tuning. Mobile Phone Detector Circuit Diagram: The circuit uses a 0.22μF disk capacitor (C3) to according the RF circuit to ensure the capability of the circuit to capture the mobile phone signal .This cellular phone detector can detect any activity of a mobile phone : incoming or outgoing SMS , video transmission or voice transmission . The C3 capacitor must have leads length of 18 mm with 8 mm spacing between leads to obtain the desired frequency .  This small disk capacitor acts as a small gigahertz loop antenna to collect the RF signals  . The CA3130 operational amplifier IC i...

The circuit below requires a double pole, double throw relay in conjunction with a single transistor to allow toggling the relay with a momentary push button. One set of relay contacts is used to control the load, while the other is used to provide feedback to keep the relay activated or deactivated. Several push buttons can be wired in parallel to allow toggling the relay from different locations. In the deactivated state, the relay contacts are arranged so the 1000 uF capacitor will charge to about 2.7 volts. When the switch is closed, the capacitor voltage is applied to the transistor base through a 560 resistor causing the transistor to turn on and activate the relay. In the activated state, the relay contacts are arranged so the 3.3K resistor and 560 ohm resistor provide a continous current to the transistor base maintaining the activated state. While in the activated state, the capacitor is allowed to discharge to zero through the 1K resistor. When the switch is again closed, the...

15 seconds delayed switch-off A good idea for bedroom lamps This circuit is intended to let the user turn off a lamp by means of a switch placed far from bed, allowing him enough time to lie down before the lamp really switches off. Obviously, users will be able to find different applications for this circuit in order to suit their needs. Circuit diagram : Courtesy Light Circuit diagram Due to the low current drawing, the circuit can be supplied from 220Vac mains without a transformer. Supply voltage is reduced to 10Vdc by means of C1 reactance, a two diode rectifier cell D1 & D2 and Zener diode D3. IC1 is a CMos 555 timer wired as a monostable, providing 15 seconds on-time set by R3 & C4. When SW1 is closed, IC1 output (pin 3) is permanently on, driving Triac D4 which in turn feeds the lamp. Opening SW1 operates the monostable and, after 15 seconds, pin 3 of IC1 goes low switching off the lamp. Notes: The circuit is wired permanently to the mains supply but current d...

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