Temporary Parking Sign with a Timer

I have always made an effort to avoid occupying others' parking spaces, but occasionally, I have no alternative. Leaving a phone number is a considerate practice, as it allows the space owner to contact you promptly. However, I have been contemplating whether it might be even more courteous to indicate the expected return time.

Manually writing the time each instance is impractical; while feasible, it lacks elegance and intuitiveness.

Initially, my plan was to utilize a microcontroller with an e-ink screen to display the estimated return time. Integrating a GSM module could further enable remote adjustments, such as reducing the timer if the return occurs earlier than anticipated. However, the internal temperature of a car can rise significantly, often exceeding 50 degrees Celsius. Under such conditions, leaving a lithium battery in direct sunlight raises serious safety concerns.

As a result, I opted for a mechanical timer, which only requires the addition of a base. Small kitchen t