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555 Photosensitive oscillator circuit

2015-01-29 18:54  
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555 Photosensitive oscillator circuit
555 Photosensitive oscillator circuit
As shown in picture 3-11, this oscillator constitutes an astable multi-vibrator along with a 555, R1, R3, C1 and a photosensitive audion, and its oscillation frequency can be calculated by this formula: f=1.44/(R+2RVT+2R3)C1 The internal resistance in photosensitive audion VT changes as light change. When exposed in a strong light, is will have a low resistance, vice versa. Therefore, the oscillation frequency changes as sensitivity of light changes, oscillation frequency can change from 1Hz to 6.5Hz. This oscillator can be used as the leader to explore the way for the blind people, or as the harbinger of dawn or can be used in other situations.