have 4 buildings, all close enough to be able to use some RF or WiFi to talk to each other, but only one close enough to the wifi hub/router.
what I would like to do is to have that one be the master and store/archive all the data from the others. temp/humidity etc. each sending data about once every 5 minutes.
but, then I want to be able to log onto the master and get graphs of the data from each.
I have the sensors doing individual SD data storage and manually swap cards.
I looked in to the on-line data sites like dweet.io, but either they want a monthly fee of there is no archive retrieval.
You have not said over what distance you need to transmit the data.
And I am not clear if you mean that one of them is situated where it could receive WiFi signals from all of the others? If that is the case then maybe ESP8266 modules would suitable. Perhaps they could send the data direct to the PC with the WiFi.
Another option might be to use nRF24L01+ transceivers in a master-slave configuration. See this Simple nRF24L01+ Tutorial
If longer range is needed the HC-12 modules have got favourable mention in other Threads but I have no experience of them myself.
XBee would give you a mesh to connect all the buildings together. You could use a raspberry pi with mysql to store the data and serve up web pages with your graphs - google charts would be one way to do that.
the first building (barn) gets a strong WiFi signal and has mains power.
the first out-building (shed) has intermittent WiFi if the wind is just right...
but, with an ESP8266 in the barn and one in the shed, they can connect without problem. the other 2 sheds are further, in a straight line and an ESP8266 in each of those can also connect to the barn.
so, the barn ESP8266 seems to be the natural point.
in looking up mesh, it seems like any point can talk to any point. seems to be complicated in concept.
If there was a raspberry Pi in the barn, it could act as the central point for each other device.
The barn seems to be the central point and each other only needs to talk to that and not to each other.
the Raspberry Pi in the barn sounds like it would work and each of the Arduinos would be able to talk to it.
I have not done any raspberryPi stuff yet. any suggestions on key words to search for ? forums ?
One way to do it is to have the Pi run a web server and have the satellite devices send their data in the form of a GET request. Search for Apache. Store the data using MySql. Build the web pages with your language of choice - PHP perhaps.
Alternatively, you could use UDP or TCP to send messages between the sensing units and the Pi.
When I did something similar (but with fewer sensing units) I used the first option using an UNO with a wifi shield and a LAMP server that I already had to collect the data. Now, the sensing unit is itself a Pi because the Arduino wifi library I had couldn't handle WPA2.
If you want to build a simple web server on an RPi (or on regular PC) I suggest you look at the Python Bottle web framework. You could have something simple working in 10 or 15 minutes. It may not have the performance or security features of an Apache server but there is a lot less to learn.
I have also used the Python peewee library to access databases - SQLite should be perfectly sufficient. It is very convenient to use because the entire database is in a single file.
At this point, security is not important. I cannot imagine anyone stealing temperature readings : )
A Pi as a web server seems to be the first step.
in my very brief searches, a PI is a bare-bones mother board with some all-in-one features like video and usb and some have WiFi. need to add storage?
pi-zero with wifi ?
or would one of the larger boards be better ?
to get started, Robin2 said a pi or a pc.... I have an extra PC with wifi dongle.
since all this is new to me, the easier the better.
I'd suggest that you start with the PC. You may want to port it to a Pi later - it'll be easier to protect if the barn is a hostile environment (temperature, humidity, mice). The Pi will be a lot more frugal on power too. They generally run Linux though, which may add to the learning curve.
The reason I have not bought an RPi is because you also need to get a screen and keyboard and I don't own a TV set that could be used as a screen. A cheap laptop comes with a battery-backed power supply, screen, keyboard and hard disk.
An RPi is physically smaller and consumes less power but I have not yet needed either of those features.
I have been using Linux on my laptops for a few years now. The last time I was using Windows regularly it was XP.
An RPi doesn't need a screen or keyboard -- I use them all the time without. In fact the GUI is so slow as to be painful.
Just like Arduino, you can and should do everything of interest in console mode, using a terminal program and a USB serial cable to any other computer, or access it via the network using ssh. Total outlay about US$ 30.
jremington:
Just like Arduino, you can and should do everything of interest in console mode, using a terminal program and a USB serial cable to any other computer, or access it via the network using ssh. Total outlay about US$ 30.
When I last enquired they don't work like that out-of-the-box.
@dave-in-nj
Trying to do something similar in a couple of months with bare ESP8266-12 modules, mounted on multiple 16-channel LED driver boards (designed and ordered) for main house lighting.
The (still fuzzy) idea is to exchange on/off/brightness data with a master, and read/control data/lights with a PC and smartphones, with web pages installed on the ESP modules (or only on the master).
New to mesh setups, and basically bad at programming.
I saw a basic ESP mesh sketch in the examples of the IDE after installing the ESP files. Don't know if that's useful.
Following this thread with interest. Please keep us updated.
Leo..
Have a look at the RPI3 with ESP8266's. I Run the Pi headless with Domoticz. Using 2 Wroom's, a 12E and a NodeMCU all with ESPEasy on them. I get temps from DS18B20's and have an LCD 20x4 on one for display.
I've been working on a Management System for over 2 years when I get a chance. I tried HC-05's, HC-12's, NRF24's and Xbee's. The ESP's are the easiest and seem to work the best. I'm not a coder and I had to work to get things going, but I got it.