Noob questions: Arduino Wi-Fi thermometer?

Question

Apologies if this is in the wrong spot, I had some trouble navigating around the element14 site.

TL;DR summary: I need a simple way to get temperature and humidity readings into a PHP script. I want it to be powered by USB, but I want the data to be transferred over wi-fi. Where should I start?

Full story:

I have a tidy little PHP website I've made that pulls data from my Nest Thermostat via the unofficial API and generates this glanceable graph to show the current comfort level in my living room:

This is useful to me and I'm happy with it, but I want to enhance it with temperature and humidity readings from my second floor and my basement.

Nest makes their own external sensors, but they inexplicably lack a humidity reading. They're also battery powered, which I don't like, and they cost $40 each. I feel like I'd be better off trying to roll my own solution here.

I have extra USB charging outlets in the spots where I'd like to stash these sensors, so I figure that's the best way to power them.

I came across this tutorial, which seems quite close to what I'm looking for: https://www.instructables.com/id/Arduino-IOT-Temperature-and-Humidity-With-ESP8266-/

This guide seems to be a few years old, though, and I'm too much of a novice to know if there are ways to simplify and improve it. For one, I don't need data logging, I just need the sensor readings to be available on demand.

Any suggestions or ideas?

ntewinkel · Accepted Answer

mp2100 wrote:

...the esp8266 is smart enough on its own...

True, I've used some inexpensive ESP based boards to log data around the house here too.

My favourite right now is still the Wemos D1 Mini. It's super affordable, like seriously less than $3 Canadian these days.

The ESP-01 in that Adafruit example is more effort to program and more effort to power, so it probably won't save you anything to go that route.

That Wemos board connects directly via USB for power and also to program the board via the Arduino IDE. I used a little old iPhone charger cube to power it where I was reading the temperature.

For sending to your own server, feel free to look through my samples. My server side scripts do more than you need, but it sounds like you can handle the PHP side well enough to just make it do what you need.

This example shows the Arduino side - basically it calls the server script with the current temperature. You should be able to expand it to add humidity without too much pain.

https://github.com/ntewinkel/electronics/tree/master/ESP-01

Hope that helps!

Cheers,

-Nico

neilk · Answer

ntewinkel kindly gave me access to his code and scripts as a starting point for my development of 2 channel ESP8266 based temperature monitoring system, with data sent over wifi to my own server. It's fairly straightforward and you should have no problem - I used a wemos D1 mini and run it on battery, via a wemos battery unit. Neil

mp2100 · Answer

A quick look at that instructables makes me think that method is ok, and not too archaic. The funny thing is, those instructions areusing the esp8266 to add wifi to the arduino. If you really want to use the arduino, that’s great. But the esp8266 is smart enough on its own to grab temperature and humidity from the DHT sensor, and I think, send it to your web client. And the esp8266 can be programmed using the Arduino IDE, just using the 8266 library added in.

Here’s one example that does that:

https://learn.adafruit.com/esp8266-temperature-slash-humidity-webserver

Gough Lui · Answer

The Wemos board is fine - I've actually used a NodeMCU Amica with CP2102 for much the same price for my outdoor solar-powered weather station programmed with the Arduino IDE, and that's been working well for me for a while. Adafruit Feather also has an ESP8266 variety as well. Additionally, Arduino has their own MKR WiFi although I've not tried it.

- Gough

luislabmo · Answer

Hi Carl, I'd say there are many ways to do what you want. PHP is mainly for web development so I'd say is better to let another program -more up to the task- to handle the sensor reading like phyton; it would be probably easier to do and documentation for this is widely available. On the webserver side you need two things: Build a python script that reads the sensor data, and formats the output: it may be a text file, it may return a string, a number, etc., or the best one -I think- is to return the sensor readings in JSON format, like: import json
print "Content-type: application/json"
print 
response={'Humidity':54}
print(json.JSONEncoder().encode(response)) From the PHP script invoke such python script to read the data, something like: <?php 
$command = escapeshellcmd('...dir..../readsensor.py');
$output = shell_exec($command);
?> As others said, the ESP8266 is perfectly capable of reading the sensor and handling WiFi communication by itself, it just requires a little bit of coding but you don't need an extra Arduino to do the work (unless you don't want to tap into the ESP8266 code). Luis

Noob questions: Arduino Wi-Fi thermometer?

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