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A simple STEREO amplifier, with minimal external components. It use one only opamp., that is capable to give output power 2X5W in the 4 ohms, with distortion 0.5%.... [read more]

This circuit is the opposite of Repeating Timer No.5. It will only begin to operate if the temperature falls below the preset level. Again - the variable resistor (preset) lets you choose the temperature below which the timer will function.... [read more]

This device was designed on request; to control the light intensity of four filament lamps (i.e. a ring illuminator) powered by two AA or AAA batteries, for close-up pictures with a digital camera. Obviously it can be used in other ways, at anyone's will.IC1 generates a 150Hz square wave having a variable duty-cycle. When the cursor of P1 is fully rotated towards D1, the output positive pulses appearing at pin 3 of IC1 are very narrow.... [read more]

This device allows one or more lamps to illuminate at sunset and turn off at dawn.Q1 and Q2 form a trigger device for the SCR, providing short pulses at 100Hz frequency. Pulse duration is set by R2 and C1.When the light hits R1, the photo resistor assumes a very low resistance value, almost shorting C1 and preventing circuit operation. When R1 is in the dark, its resistance value becomes very high thus enabling circuit operation.... [read more]

This circuit is intended to be placed in the same box containing the loudspeaker, forming a compact microphone amplifier primarily intended for speech reinforcement. A device of this kind is particularly suited to teachers, lecturers, tourists' guides, hostesses and anyone speaking in crowded, noisy environment. The circuit's heart is formed by the TDA7052 Audio power amplifier IC, delivering a maximum output of 1.2W @ 6V supply.... [read more]

This circuit generates an astonishingly real imitation of the chirping of the cricket. A suitable audio wave form is generated by IC2 and related components, driving the loudspeaker through Q1. To allow a more real-life behavior, the chirp is interrupted in a pseudo-casual way by two timers built around IC1C and IC1D, whose outputs are mixed into IC1B and further time-delayed by IC1A, driving the reset pin of IC2.... [read more]