Advice choosing main board and shields for specific project

Projects General Guidance
1

Hi All,

I am a newbie to arduino and find myself a little overwhelmed by the variety of options. I would greatly appreciate if someone could give me some advice on how to create a package with the following component abilities:

  1. real time clock (hopefully to keep time without power applied) accessible through programming
  2. two relay contacts suitable to drive motor relays
  3. at least two spare ADC channels, three better, capable of 0 to 12 volts
  4. some sort of removable memory (sd card?)
  5. 5 volt main operation voltage.
  6. rfid reader

and of course, as inexpensive as possible!

thanks for the advice

2

The RTC and SDcard together suggests looking at the various data logging shields
which normally do both.

Analog inputs will be 5V on a 5V system - resistor dividers can be used to increase the input
voltage range but that's for you to do.

two relay contacts suitable to drive motor relays

Huh? Do you just mean two relays? Contacts don't drive relays,
relays drive contacts.

3

Thanks for the reply...

to clarify, the need is to have relays on board that can drive larger relays that then drive large motors (winches).

I assume your answer means none of the native arduino boards have a RTC included?

My main question is, which main arduino board is the best option for this type of application?

4

What is wrong with just an Uno and some modules?

The most limiting thing you psted is "at least two spare ADC channels, three better, capable of 0 to 12 volts". Maybe you could say a word about that requirement.

5

Sure, and thanks for any advice.

I need to monitor the voltage of a 12 volt battery (that is powering the system by the way) as well as the voltage coming out of a solar cell charging it. I'd like to record both voltage levels every 5 minutes with wall clock timestamps. The third channel would be to a separate solar cell to monitor light levels and detect sunrise / sunset (not sure how reliable the charging solar cell is at this).

I also need to record tags going by with a 125khz rfid reader

And I need to run a winch forward and backward for a few seconds every hour or so through daylight hours, depending on voltage levels of the battery and charging rate (i will develop an algorithm to control this)

I "think" the uno is a good choice, it seems the most compatible and powerful enough. Then I think i would need a data logger shield with RTC as well as SD card and an rfid shield. I assume I can piggyback these shields onto the card. The rfid antenna would have to be remote.

the whole setup can run on either 5v supply or 12v supply, as I have both available, but the voltage from the solar charger going to the ADC channel could be as high as 25 volts.