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555 hand-wave stop noising electric clock circuit

2017-01-08 15:35  
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555 hand-wave stop noising electric clock circuit
When the electric clock goes to the alarm moment, the contact point K1 of the original movement closes (the closing time is about 2 minutes), VT5 conducts, the additional circuit gets the power. The astable multivibrator which is composed of the left part (1/2 556) of the IC1(556) and the R9, R10, C7 starts oscillation, the oscillation frequency f=1.44/(R9+2R10)C7, the parameters of the figure has the oscillation frequency of 38kHz, it outputs the square wave to drive the infrared emitting diode LED(HG411). When the hand is near the probe, the infrared ray which is reflected by the hand is received by the VT1, then this infrared ray is selected by the frequency-selecting amplifier which is composed of the VT2 and L1, C3 to rise the VT3's Vc.