555 film cans-show lan activity & exposure timer circuit

Published:2011/5/21 8:12:00 Author:TaoXi | Keyword: film, cans-show, lan activity, exposure, timer circuit | From:SeekIC

As the figure 17-2 shows, the step-down rectifying power supply spllies the voltage of VDD=+12V to the timer. The timer uses three pieses of 555 as the core. IC1 is the long timing circuit, when you press AN, IC1 and IC2 reset together, IC1's timing time is td1=1.1RP1C1，td2=1.1RP1C2, and the value depends on the different films and different exposure time. When the warning time is up, J1-1's NC contact point cuts off, IC2 and IC3's power supplies are cut off. The 1 minute timer is composed of the IC2 and R3，C3, when you press AN, J2 closes to connect the J2-1.



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