In an IoT node I use an AM2315 sensor to measure temperature and humidity. This sensor can be connected via I2C bus to a NodeMCU module. The results of these periodic measurements are presented here.
On my location these days we had negative temperature on the Celsius scale for the first time in this autumn.
What happened? I had to see wrong temperatures in my graphs.
I looked for the root cause and found that in the used library AM2315.lua the range below 0°C was not handled. The MSB of the temperature value is set in the case of negative temperatures. Therefore I masked this bit and if set the value is multiplied by -1. If you use customized firmware the bit module must be included.
Here are the modified lines for AM2315.lua:
h = string.byte(b) * 256 + string.byte(b) --humidity
h = h / 10
-- MSB is set for negative temperature
t = bit.band(string.byte(b), 127) * 256 + string.byte(b) --temperature
t = t / 10
if bit.isset(string.byte(b), 7) then t = -1 * t end
You will find these modifications on https://github.com/tectiv3/am2315-lua, now.
Finally, here is a temperature graph from today. Winter is coming now 😉
… seen @ Mini Maker Faire Zurich 17./18. September 2016.
A very good example for a battery-powered wireless IoT-Node. Have a look to Lambda Nodes for further information.
Now, after two weeks of vacation, the sensors were in operation from 2016-05-17 until now and the battery condition is very well. This means an uninterrupted run time of 28 days until now.
You can follow the status of this IoT Node at www.ckuehnel.ch/AM2315@NodeMCU.html. Here is a screen shot of today’s results.
The following images show that already little sun as today helps to recharge the LiPo accu of the solar-powered AM2315 sensor.
As you can see, for mid of May it is a little bit cold. After noon, the clouds thinned slightly and the temperature grows up. The IP camera image shows the cloudy sky.
But, the prognosis for the afternoon is not so bad. Look at the evening what happened.
To build an autonome weather station I started a test with a solar-powered AM2315 Sensor. The data are uploaded to Thingspeak.com and are presented over an own website.
The AM2315 is a temperature & humidity sensor with an I2C-interface in a nice enclosed style. The sensor contains a DS18B20 temperature sensor and a capacitive humidity sensor. A microcontroller inside builds the sensor interface and works as an I2C-slave.
For outside measurements it is also advantageous that the AM2315 comes in a rugged case with mounting bracket. While it is not rated as ‘weatherproof’, it is more suitable than SHT PCB-breakout sensors for measuring outside.
After crimping a Grove-connector we can connect this sensor to a Grove Arduino sheld hooked on a Wemos D1 board, for example. Or you connect the wires to a Wemos D1 mini.
At Github you will find an AM2315 Lua module and it is easy to integrate the AM2315 into your own application. I have included the AM2315 sensor into my DHT11 network and it sends now outside data to the MQTT. Its ID is ESP8266-13972685.
The data coming from the AM2315 sensor are marked red in the screenshot while the data of another outside sensor ASH2200 are marked orange. The two sensors are outside but at different locations.
The software am2315.lua and am2316_mqtt.lua is on Sourceforge and Github.
To reduce the power consumption of my IoT button it must go into sleep mode after sending its message. I measured a current consumption of about 100 μA in sleep mode w/o any hardware changes. To get further reduction of current consumption you can remove the LED at pin D0 (GPIO16), for example.
Continue reading “IoT Button (2nd)”