I'm trying to design a small home alarm system. The setup will consist of a number of sensor modules to monitor the perimeter of the garden and one or more base stations. I like to use wireless communication between the remote sensors and the indoor base station(s) and high frequency stuff is an extremely weak point in my knowledge.
I prefer not to specify a maximum distance (I hate limitations) but for the current setup it is between 60 and 100 meters.
I know there are a number of options (I might have missed some) like Wifi, Bluetooth, nRF24 and 433 MHz. I think the first two can be dropped due to range (and bluetooth only seems to support 7 devices). Leaves the nRF24 or the 433MHz.
Which would be the better option. I would prefer the nRF24 as it supports 2-way communication out-of-the-box but will it be able to go through (brick) walls? The 2-way communication however is just a nice option and not necessarily a requirement and I assume I can build it as well with 433MHz if needed.
The sensor modules will use an ATtiny and will be battery powered; the base station(s) some form of Arduino (Uno for the development, a Nano or similar (depending on voltage requirements)).
Any advice or alternative suggestions; cable (with e.g RS485) is the last option if nothing else is possible.
The setup will consist of a number of sensor modules to monitor the perimeter of the garden ............. for the current setup it is between 60 and 100 meters.
Wow that is a big garden. :o
That sort of thing is pushing the limits of what you normally achieve with legal stuff. You could try this:-
Thanks for the reply. It was actually one of your replies in another thread about communication between two buildings that triggered the question.
The garden is not THAT big (local reference ;)); it's about 50 meters long and between 20 to 30 meters deep. One base station will be in a house in one corner of that garden. The furthest sensor module will be diagonally across the garden and Pythagoras says that it will be roughly 60 meters. The 100 meter range is basically a future proofing.
I could not immediately find a costing (should have mentioned that) in / via your link; if it's not in the same ballpark as 433MHz or nRF24 modules, it's not an option as it's a hobby project for now.
Maybe I must just buy both options and test what works.
I have been using RFM12B transceivers for years now. With an attiny85/84, battery life is going on for more than 2 years now. I'm getting excellent reliability from the RFM12B's over 120 meters, and that's from the backyard going thru walls into the house where the receiver is located.
I use the attiny85 for sensors that only require one pin, and the attiny84 for multiple sensors(dht22, bmp085, precipitation gauge, etc.).
I use an Arduino YUN as the receiver, and send the sensor data to thingspeak. I was using an Android app to display the sensor data, but instead, I created a web page to display the sensor data. I can now access the sensor data web page from anywhere.
The furthest sensor module will be diagonally across the garden and Pythagoras says that it will be roughly 60 meters. The 100 meter range is basically a future proofing.
Still more expensive than expected but maybe a possibility.