The figure below shows a very interesting project of an automatic electronic weekly calendar circuit with alarm. The circuit will show a visual indication of each day of the week by activating an LED. It can also make alarm on the selected day when sun rises, the length of alarm can also be increase or
decrease as desired. The circuit can also be used as a weekly timer and a relay can also be connected in the place of peizo buzzer.
The circuit is using three ICs with some discrete components. A light detector circuit is built around the IC1; its output at pin 3 goes high at daytime and low at night. An LDR is used as a light sensor. The sensitivity for detecting light can be adjusted with the 15K variable resistor. The IC2 is a CMOS decade counter IC. It has 10 outputs from which we have used 7, which are from Q0 to Q6. An LED is connected at each output with name of a day marked on it. The IC will activate a new LED and close the previous each time the voltage at its clock input pin 14 goes low to high. The alarm circuit is built around the IC3, it will give a beep for 10 second and then goes off automatically. The time period of the alarm can be increase by increasing the value of capacitor Cx.
After completing the circuit fit it in a suitable casing and fix it at a place, which gets sunlight or daylight. For making the circuit to work properly make sure that the circuit will not get much light at night from any source.
The operating voltage of the circuit is 6V to 15V DC, make sure to use the same voltage relay as the supply voltage.