Device Eternal alarm clock. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Device Eternal alarm clock. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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The task of waking up a sleeping person with the advent of dawn can be solved by assembling the proposed signaling device (see Figure a). It does not require adjustment and it does not need a power source - its role is played by two photodiodes (VD1, VD2) connected in series. The BF1 uses an imported piezoceramic transducer with a built-in oscillator as the sound source.

Device Perpetual alarm clock

Photodiodes, illuminated by direct sunlight, produce an EMF of about 12 V at a load current of 600 μA, which is enough for a very loud operation of the emitter even against the background of street noise. The sensitivity of the photodiodes is enough to work in the presence of light clouds in the sky. By installing this device in the evening on the southeast window and directing the photodiode lenses slightly above the horizon line, you can wake up early in the morning to the mournful peep of the alarm clock.

Many "red" LEDs, when illuminated with bright light, also produce an EMF of about 1,3 ... 1,4 V. The only trouble is that the current that they are able to give to the load is negligible. But among the many LEDs available to the author, there was a record holder, an ultra-bright red LED from the Kingbright company, type L-1513SRC-E. It could be assumed at first that if it shines brightly, then it might work well in valve mode as a miniature solar cell. And so it turned out.

With precise "aiming" at the Sun, this LED, absorbing solar energy, gives 0 9V at a current of 250 μA (Fig. b).

Device Perpetual alarm clock

The sound volume is quieter with it, but you can increase it by turning on in parallel (and pointing exactly at the flaming ball) several LEDs.

Author: A.Butov, village of Kurba, Yaroslavl region

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