Early bird LM324
Let's make an early bird that begins chirping when it grows light in the morning. No doubt you suspect we use CdS cell: yes you're right.
In this project the op amplifier IC is used as the square-wave oscillator and the sweep oscillator. When the resistance of the CdS cell goes down, the switching transistor Q3 turns ON, and power is supplied to the circuit.
When you finish wiring up the circuit, turn the 100K control volume tuner fully clockwise. Set the 50K control volume in the 12 o'clock position, and turn power ON.
You'll hear the early bird chirping from the speaker. Rotate the 50K control volume, and you can change the tone of the chirp. Set the 50K control volume in the position where you can hear the twitter you like the best.
The 100K control volume adjusts how much brightness is required to wake up the early bird. Adjust to the best point so you can wake at the time not too late to school!