555 automatic exposure timer circuit (1)

Published:2011/5/22 20:06:00 Author:TaoXi | Keyword: automatic exposure, timer | From:SeekIC

As the figure 17-6 shows, the circuit is composed of the step-down rectifier circuit and the 555 monostable circuit. The monostable circuit is composed of the 555 and photoconductive resistance RG, C2, when you press the button AN, 555 circuit sets, pin03 has the high electrical level to trigger the SCR, the expose lamp turns on. When the photoconductive resistance has no illumination, the resistance is so big, when the light turns on, the resistance of the photoconductive resistance reduces, the power supply charges C2 through the photoconductive resistance, when pin-6's voltage is higher than 2/3VDD, pin-3 has the low electrical level, SCR cuts off, the light turns off.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Control_Circuit/555_automatic_exposure_timer_circuit_1.html

Print this Page | Comments | Reading(3)