The internal lighting lamp state test circuit of 555 fridge

Published:2011/5/27 0:11:00 Author:Borg | Keyword: internal lighting lamp, test circuit | From:SeekIC

555, R2,R3 and C1 consist a coercive multi-oscillator, the 4-lead of the coercive terminal links to the C terminal of LED 3DU5, under the light, 3DU5 is in a low resistance, so the 4-lead of 555 is in a low LEV and it is forced to be reset, the oscillator stops working and the loudspeaker is quiet; when there is no light, 3DU is blocked and its resistance is high, the 4-lead is in a high LEV, the 555 oscillator is starting to work and it frequency is f=1.44/(R2-2R3)C1The shaking frequency of the parameter in the figure is 993Hz. Figure 13-20 The internal lighting lamp state test circuit of the fridge



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