Once, the digital alarm clock starts the alarm signal, we need to stop this alarm. The potentiometer is used to control the volume and pressure of the alarm signal from the buzzer. The alarm output of the IC1 (LM8560) is given to the input (Pin 3) of the IC2 (LM386) through a potentiometer P1. Hence, the IC LM386, which is a power audio amplifier, is used in the digital alarm clock circuit. But to drive these special buzzers, we need an audio power amplifier. But in order to get special alarm tones from the digital alarm clock, we can use special alarm signals. This can be connected to a small buzzer directly for alarm output. Once the alarm is set successfully, the digital clock IC waits for the alarm time and once the alarm time is reached, an alarm output at the Pin 3 is generated. In order to set the alarm, we need to hold the switch S3 and set the Hour and Minutes of the alarm time by using switches S1 and S2 respectively. In order to differentiate between the setting of current time and alarm time in the digital alarm clock, we use the switch S3 which internally triggers the alarm display of the LM8560. Once the time is set, we can set the alarm using the switches S1, S2 and S3. The duplex display is a 4-bit seven segment LED display, where two bits are for displaying the Hours and two bits are for displaying Minutes and the Hour and Minute bits are separated by a colon. LM8560 automatically triggers the display connected to it and the time will be displayed on the duplex LED display. Switch S1 is used to set Hours and S2 is used to set Minutes. In order to set the current time, we use the switches S1 and S2. This is the current time to be displayed. After switching on the power, we need to set the time. In relation to the input of the IC1, corresponding inputs to the cathode of the display are given through the diodes (D2 and D3). This signal can be supplied from the mains supply using the resistor R1 to the Pin 25 of the IC1. IC1 (LM8560) works at a frequency of 50/60 Hz. The input from the mains is given to the transformer which converts the input voltage to 12V AC.Ī diode (D1) and a capacitor (C1) are used to convert this AC voltage to DC and supplied to the Vdd (Pin 20) of the IC1. The working of the above shown digital alarm clock is as follows.Īs explained in the component description, the heart of the digital alarm clock circuit is the digital clock IC LM8560. The components required and the complexity of the circuit are less. The circuit shown above can act as a simple digital alarm clock without requirement of any programming. Digital Alarm Circuit WorkingĪ digital alarm clock is a very useful device as it can display the current time as well as function as an alarming device. Transformer (T1)Ī transformer is used to step down the 220-240 V AC supply to 12 V AC supply. A buzzer is used for this purpose which is driven by an audio power amplifier. The main function of the digital alarm clock is to signal an alarm at specified time. They work in relation to the input of the LM8560. Diodes D2 and D3 act as switch signal generator to the cathode of the duplex display. Diodes (D1, D2, and D3)ĭiode D1 in combination with the capacitor C1 will produce a DC voltage that is supplied to the IC1 (LM8560). When setting time and alarm in the digital alarm clock, both Hours and Minutes can be set separately using these switches. These four switches are used to set time, set alarm and turn off the alarm. There is no need for any extra drivers to drive the display unit as all the required drivers are built in to the digital clock IC. In the digital alarm clock, to display the information like current time, alarm notification etc. The alarm output of the LM8560 is given to power amplifier through a potentiometer. It is used in the circuit to drive the alarm buzzer. It is a low voltage audio power amplifier. The functions of the IC LM8560 are display of current time, alarm support, snooze function and supports 12 HR and 24 HR time format. The drivers required to drive a duplex LED display to show the time are in-built to the IC. It is an alarm equipped digital clock IC. The heart of the digital alarm clock is the IC LM8560.
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