So, I basically need to have one receiver Arduino and multiple transmitter Arduinos (probably ~5). Goal is to see when the windows are open in my apartment. There is a magnet on every window, and a bare Atmega328p with a transmitter. When a window is opened, it sends a byte to the receiver Arduino. It's powered by two AA batteries (3V). Station is 5V and I don't need any power savings there.
Now, the problem I'm encountering is the range. The apartment is not very large, but it would have to penetrate walls. All in all, 10 meters with 2 walls should be the most it has to overcome.
Can I achieve this with this product:
Or, do I need something more expensive? If so, the receiver cost is not that important (RXB12 is completely fine), but transmitter should be cheap. Also, what transmitters do they use in car remotes, and can I use them with Arduino? Because their range is completely fine for me.
If this is a security system then it would be more reliable if it uses wires rather than wireless.
It's not a security system. It just needs to turn the AC on and off.
Yes, that transmitter and receiver will do what you want.
Product link corrected: 433 Mhz Superheterodyne RF Receiver and Transmitter Module ASK kits with antenna For Arduino uno Diy kit 433Mhz Remote controls|module connector|module enginemodule gear - AliExpress
The receiver is the superheterodyne version, so that is the proper one.
The transmitter is nowhere near as critical. That one, using a PLL multiplier should be fine. The Web page notes that it is permanently enabled in this module, so while it cites "shutdown mode current is less than 1µA", I am not sure that it actually is in "shutdown" when always enabled and indeed has such a low standing current. Since you mentioned these, I put a couple on order so I may be able to check this sometime in the next three months.
I presume your bare Atmega328ps will be sitting in sleep mode using their internal clock and waking periodically to enable INPUT_PULLUP and read the reed switch then disabling it. Even with the superheterodyne receiver, you will be sending a repeated code for the receiver to verify and presumably identify the particular transmitter (even if your application does not really need to know which, most of the time).