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How to build electronic timer? Answered

I would like to build a 24h timer which will operate for 1min at each iteration.
For example: each day at 20:00 the timer will light a led for 1 min.


Depends on how accurate you need it to be.

Accurate then use a micro and RTC

Vaguly accurate or able to reset daily use a 555 timer.

lots on the web for these.

Use a RTC (Real Time Clock) module with an Arduino and your set. Time stamp can be displayed on a 7 character display or a small LCD. You'll get accurate timing as well. a 555 can drift a bit.

Obviously a digital timer for a few bucks from the shop is not what you are after.
There is plenty of info on using a NE555 timer IC for tasks like this, including Youtube videos and datasheets.

It is basically just a matter of using the right resistors and capacitors.
For more precision like using a clock you can misuse an old digital clock.
Use the alarm signal for the speaker/beeper to switch a flip flop on for one minute.