135 film positioner (C180、TWH8751) circuit

Published:2011/4/26 21:44:00 Author:TaoXi | Keyword: film positioner | From:SeekIC

The 135 film positioner (C180、TWH8751) circuit is as shown. This circuit is composed of the counter C180 and TWH8751. And the TWH8751 forms the oscillator with 1kHz oscillation frequency. The count switch K2 composed of the a wire and the device body at the position of 135 film's holes, when the 135 film moves, each time the contact plate contacts the body, this circuit produces a count signal. When you open this device, the contact plate of first hole contacts the body, C180 has been reset. When the nineth hole of the photo comes, there will be 8 count signal, so the Q4 of C180 has high-level voltage to turn on the BG, pin-4 outputs the signal to drive the speaker to tell master the photo is in position. When the circuit is debugging, you should close the switch K2 first, then close the power switch K1 to make the LED light, Q1~Q4 have low-level voltage. Then turn on and off the K2 eight times, Q4 has high-level voltage.



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