Starting Arduino

I would like to know about boards and modules I need for real time clock and programmable time controling . For example : I need to power on and off some loads at differents hours a day for some periods ( seconds or minutes )

Regards

Hello, it's Kind of difficult to answer questions when no specific question has been asked.

In reference to boards, you can use any of the Arduino boards. A specific board is usually Chosen for a specific Project due to specific factors. For example, the Mega has more Memory and I/= Pins so if you Need the extras, the Mega is the way to go. Another factor is power usage. Some boards Need more milliamps than others. You Need to state your requirements for us to be able to make specific suggestions.

Similarly, you can use any RTC breakout you find based on availability, Price, and the required communications you want to use (I prefer I2C). Again, state your requirements and we can make suggestions.

As for the programming, make a structure of pin number, current state, time to start being on, time to stop being on. Put the Arduino to sleep, wake it up once a Minute or so and run through your structure. If it's off and time to turn it on, turn it on. If it's on and time to turn it off, turn it off.

You might want to take a look at the "Time" library, and maybe also the "TimeAlarms" library, along with one suitable for the RTC that you choose.

And when choosing an RTC module, it's much better to get a DS3231 or DS3232 - based module, and not a DS1307 or DS1302. The DS323x chips are much more accurate. They have an integrated temperature compensated crystal oscillator, whereas the DS130x chips don't.

And unless you need more than a total of 19 I/O pins, an UNO is a good board to start with.