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555 E-Lark Circuit changing with Light intensity

2015-02-05 03:13  
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555 E-Lark Circuit changing with Light intensity
555 E-Lark Circuit changing with Light intensity
This E-Lark circuit can make a fluctuating and toned sound when exposed in light of different sensitivity, it is like that in the figure 3-22. The core part of the multi-vibrator is the time-based 555 circuit, which consists of 555, R1, RG and C1.This multi-vibrator concatenates a photoresistance (RG) on its charge and discharge loop, resistance value of this photoresistancewill change as the sensitivity of light changes. This attribute can be used to change the charge and discharge time constant and the frequency of the multi-vibrator, that is, f=1.44/(R1+2RG)C1, GR refers to the photoresistance resistance value in different light sensitivity. This changeful frequency signal drives the VT1 and makes various bird sounds through the speaker when its current is limited by R2. We can choose photoresistance series MG41~MG45 used as RG, MG45 is a nonhermetic instrument and its response wave ranges from 0.56 to 0.58μrn, low-power tube 9013 can act as VT1. If you want to strength the vocal power, 8050-type tube can be used. (Pcm=1W,Icm=1.5A, fnt=190MHz)