So, I’ve got a very basic datalogger working with some sensors I have (LM35 for the temperature and PT550 for the lighting). Will have to do more work with RRD to get the hang of the charting, etc. but first effort is up anyway
Charts
RRD Setup
Details on the backend RRD database – I’ll update this as sensors are added and I adjust it to suit my requirements.
Database
rrdtool create database.rrd --step 60 \
DS:temp:GAUGE:120:0:100 \
DS:voltage:GAUGE:120:0:5 \
DS:env-light:GAUGE:120:0:6000 \
RRA:AVERAGE:0.5:5:288 \
RRA:MAX:0.5:5:288 \
RRA:MIN:0.5:5:288 \
RRA:AVERAGE:0.5:60:168 \
RRA:MAX:0.5:60:168 \
RRA:MIN:0.5:60:168
Image Creation
This runs as a cronjob every 5 mins to update the charts. The other option is to call it from a PHP page and trigger a generation upon page click.
rrdtool graph temp-24.png -a PNG -w 550 -h 240 -v "Degrees (C)" \
'DEF:ds1=database.rrd:temp:AVERAGE' \
'LINE1:ds1#FF0000:Temperature' \
GPRINT:ds1:MAX:"Max %6.2lf %s" \
GPRINT:ds1:MIN:"Min %6.2lf %s" \
GPRINT:ds1:AVERAGE:"Avg %6.2lf %s" \
GPRINT:ds1:LAST:"Curr %6.2lf %s\n" \
-t "24 Hour Temperatures"
rrdtool graph light-24.png -a PNG -w 550 -h 240 -v "Lux" \
'DEF:ds1=database.rrd:env-light:AVERAGE' \
'LINE1:ds1#00FF00:Light' \
GPRINT:ds1:MAX:"Max %6.2lf %s" \
GPRINT:ds1:MIN:"Min %6.2lf %s" \
GPRINT:ds1:AVERAGE:"Avg %6.2lf %s" \
GPRINT:ds1:LAST:"Curr %6.2lf %s\n" \
-t "24 Hour Ambient Light"
