Électronique / Electronic
Wouldn't you like to make a kitchen timer that you can use for cooking meals?
This timer is the same as the test timer in the last project (Study Timer) except for one point. It gives out a buzzer sound for 1 to 2 seconds and automatically stops.
Slide the switch to OFF and build the circuit. When you finish assembling the project, turn on the power by sliding the switch to position ON.
Set the control to position 2 on the dial, and press the key to start the timer. After about 40 seconds, the timer sounds for 1 to 2 seconds and stops. Use the graph you made in project Study Timer to preset this timer.
Look at the schematic. When the preset time is up, the comparator (IC 2) sends out an output. After a time lag of 1 to 2 seconds produced by R2 and C2, the transistor Q1 turns on to stop the multivibrator. The silicon diode discharges C2 and restores the circuit to the original state when the timer is restarted.