Home Assistant is an open source home automation platform that can monitor and control smart home devices and it integrates with many of other common systems.

Home Assistant installation is targeted for Raspberry Pi’s but other hardware options are available.

I was very impressed how easy it was to install Home Assistant and get a basic home integration system up and running.

There is a huge number of integration solutions (1500+) that connect to most of the mainstream products. However if you want to do some custom programming with connections to Arduino or other Raspberry Pi or PCs there isn’t an easy “out of the box” solution.  To solve this requirement Home Assistant has included Node-Red as an add-on.

Node-RED is a visual programming tool for wiring together hardware devices, APIs and online services.

For information how to install Node-Red on Home Assistant see the HA documentation. (I wrote a blog for my installation).

Home Assistant History

The default installation of Home Assistant has history enabled, and the data is stored in local SQLite database (home-assistant_v2.db) within your configuration directory unless the recorder integration is set up differently.

Charts of sensor history can be show in the Home Assistant Overview pages or as dialogs.

Using Node-Red with HA History

The Node-Red installation has a number of Home Assistant nodes that allow sensors data to be read and created. For viewing history the HA get history node is used.

A simple manual test circuit to get history would have: an injector, a get_history and a debug node.

By double-clicking on the get history node its configuration can be defined. For this example a sensor entity id of sensor.cpu_temp is used with a 10 minute (10m) time scale. When the injector is toggled the debug window will show an array to data and time entries.

3 Button History Chart

The logic to create a 3 button history chart would use: 3 dashboard buttons, 3 get history nodes, a Javascript function, and a dashboard chart node.

The Node Red chart node typically does local historical storage within the node itself. However the chart node can also be used to read external data and show a line chart of the data,nothing is stored locally (more info on this).

A javascript function node can be used to format the data into the required form:

//
// Format the HA History results to match the charts JSON format
//

var series = ["HA Values"];
var labels = ["Data Values"];
var data = "[[";
var thetime;
 
for (var i=0; i < msg.payload.length; i++) {
    thetime = (msg.payload[i].last_changed); // Note: check your format?
    data += '{ "x": "' + thetime + '", "y":' + msg.payload[i].state + '}';
    if (i < (msg.payload.length - 1)) {
        data += ","
    } else {
        data += "]]"
    }
}
var jsondata = JSON.parse(data);
msg.payload = [{"series": series, "data": jsondata, "labels": labels}];
return msg;

The payload data will be in the format of:

If everything is formatted correctly the Node Red dashboard page should look like:

For a more flexible presentation it would be good to use adjustable time periods.

Final Thoughts

For simple historical storage I found that the built-in History worked fine, however if you’re looking for custom long term storage then the InfluxDB add-on to HA might be a better solution.