This is a project of an adjustable hourly chime & switch circuit using 555 IC or we can also say it 555 alarm clock. The circuit will produce an hourly time signal / beep after every hour and also make the LED light up with the signal. The circuit is adjustable from few minutes to 1.5 hour.
It is an interesting project and can be used for variety of purposes. For example it can be used as a time reminder, you can also use it in quizzes and competitions and adjust it to give time signal on a preset time like after every 5 to 10 minutes or more. A relay switch can also be connected at the output of the IC to activate any AC or DC device with the time signal, you can also connect any big alarm or bell with the relay, the figure 2 shows the circuit with relay.
The circuit is built around a 555 timer IC. The 5M variable resistor is used to adjust the gap between the time signals from few seconds to 1.5 hour. The time gap can also be increased by increasing the value of the 1000uF capacitor. For example a 2200uF capacitor can increase the time gap to around three hours. The circuit can be operated from 4.5 to 12V DC.