NE555 exit reminder

Boiling water on a gas stove, heating water on a solar panel, turning on the TV, turning on the lights, forgetting to bring keys or cell phones... It is easy to have these kinds of things happen when you rush out. The exit reminder can help you solve the above problems better.

This device includes two parts: delayed power-off and voice playback. The delayed power-off is based on the 555 circuit. When the switch K is pressed, the 555 integrated circuit is powered, the ② pin is triggered, the ③ pin outputs a voltage of about 3v, the relay J works, and JK is connected, forming a self-locking state to power the voice playback part. As the charging voltage of the capacitor C1 increases, after a delay of about 3 minutes, the ⑥ pin is triggered. The output state flips, and the relay is powered off and released. The voice playback part is powered off and stops working. The LED is a power supply status indicator, and the K switch can be used as a doorbell button. The voice playback can use an ordinary MP3, which requires an additional first-level amplifier to drive the speaker (8Ω small dynamic type), or an MP3 playback speaker. Record content as needed, such as: Please check the gas, solar water supply, don't forget to bring your keys...

The principle of this device is simple, but the production should be exquisite. It can be made into a handicraft or integrated with a key box and placed in a place where it is easy to find when going out. As long as you develop a habit of pressing the switch button when going out, the problem can be solved.