dht22_display

A simple sketch that displays temperature and humidity from a DHT22 sensor to a TM1637 display. Data from the sensor are also logged into an RRD database.

Introduction

My first simple project in Arduino that was made just for fun. If you have any suggetions for improvements or any bugfixes, please feel free to create an issue.

Hardware requirements

• Arduino Yun
• 4 digit display driven by a TM1637 chip
• DHT22 sensor
• SD card (in case you need logging to be performed on the Arduino Yun)

Library requirements

• TM1637Display (https://github.com/avishorp/TM1637/)
• DHTLib (https://github.com/RobTillaart/Arduino/tree/master/libraries/DHTlib)

Installation

Copy arduino folder to an SD card.

Commands for RRDtool

1. Create an RRD database (most preferably inside arduino/www folder).

   rrdtool create temp.rrd --step 5 \
     DS:temp:GAUGE:20:0:U \
     DS:hum:GAUGE:20:0:100 \
     DS:hi:GAUGE:20:0:U \
     RRA:AVERAGE:0.5:1:1000
     ```
   
   

2. Use the following script to insert data from the Arduino to the DB.

   while true
   do 
     rrdtool update temp.rrd $(curl  -q http://localhost/data/get/ 2>/dev/null |./readSensor.py) && \
     echo "Updated" && sleep 5 
   done
   

3. Plot a graph using the following command.

   rrdtool graph temp.png --rigid --lower-limit 0 --upper-limit 50 \
     --vertical-label 'Temperature in C' --right-axis-label 'Percent' \
     --right-axis 2:0 --start -900 --end now \
     DEF:temp=temp.rrd:temp:AVERAGE LINE:temp#54EC48:"Temperature":STACK \
     GPRINT:temp:MIN:"min\: %3.2lf %s" \
     GPRINT:temp:AVERAGE:"average\: %3.2lf %s" \
     GPRINT:temp:MAX:"max\:%3.2lf %s\n" \
     DEF:hum=temp.rrd:hum:AVERAGE CDEF:s_hum=hum,0.15,* \
     LINE1:s_hum#8BBFFF:"Humidity":STACK \
     GPRINT:hum:MIN:"min\: %3.2lf %s" \
     GPRINT:hum:AVERAGE:"average\: %3.2lf %s" \
     GPRINT:hum:MAX:"max\: %3.2lf %s\n" \
     DEF:hi=temp.rrd:hi:AVERAGE CDEF:s_hi=hum,0.15,* \
     LINE1:s_hi#F29D00:"Heat Index":STACK \
     GPRINT:hi:MIN:"min\: %3.2lf %s" \
     GPRINT:hi:AVERAGE:"average\: %3.2lf %s" \
     GPRINT:hi:MAX:"max\: %3.2lf %s\n"
     ```
   
   

4. Visit http://arduino.local/sd/temp.png and check the result.