555 simple automatic exposure circuit

Published:2011/5/24 2:51:00 Author:TaoXi | Keyword: simple, automatic, exposure circuit | From:SeekIC

As the figure 17-4 shows, this circuit is composed of a 555 and some resistance, capacitance components. The 555 is the monostable delay time circuit. If you press AN, the 555 sets, pin-3 has the high level voltage, the exposure light or the actuator turns on. The silicon photovoltaic cell suffers the illumination to produce the light current I, and this light current I charges C1, when C1's voltage is more than 2/3VDD, 555 circuit resets, pin-3 has the low level voltage, the exposure light or the actuator has no power to work. The threshold electrical level can be adjusted by RP1, the value is more than 1.4V.



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