555 automatic exposure timer circuit (2)

Published:2011/5/22 20:13:00 Author:TaoXi | Keyword: automatic exposure, timer circuit | From:SeekIC

As the figure 17-7 shows, the monostable delay circuit is composed of the 555 and C1, cadmium sulfide photoresistor RG.etc. You install the RG near the photo, when exposure, if you press AN, 555 sets, J closes, the exposure light (white) turns on. If the illumination is strong, RG has the low resistance, td=1.1RGC1; if the illumination is weak, RG has the high resistance, td will be long. When the time of td is up, J releases, the white light turns off, the red light turns on, the exposure time complete. Figure 17-7 The 555 automatic exposure timer circuit (2)



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