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 NXP Semiconductors


  • Alarm Timer with Multiple Preferences

  • Created: Sep 16, 2014

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Summary

The applications for this project are alarm and switching with adjustable period or the countdown time. This project can be used to switch ON/OFF a device with the absence a person.

The 74LV4060D (14-stage binary ripple counter/divider and oscillator) is used for the operation; it is configured to set a countdown time that can be adjusted through pins RTC, CTC, and RS. The resistors and capacitor connected at these pins will determine the frequency of the 74LV4060D IC. 74LV4060D has ten output pins (Q3 to Q13, w/o Q10) with different trigger time, each with twice the time of the lower Q (e.g. TQ4 = 2 x TQ3). The output produces a signal after the countdown time is set; this triggers the NPN transistor switching the 555-timer circuit.

The ICM7555 timer is configured as monostable multivibrator, it acts as the switch of the buzzer. The time duration of the buzzer is also adjustable through the resistor and capacitor at pins DISCHARGE and THRESHOLD of the ICM7555 (t = 1.1RC). The RESET button at the 74LV4060D is simply to reset the timer back to start.

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