[NCLUG] dynamic graph on web page

[Daniel Herrington]

Thanks for the pointers about rrdtool.  I decided to try it out on my
robot, since it already has some sensors and an ADC.  (Why not, since
it's running Redhat 4. ;-) I haven't added temperature and light
sensors yet, but I have tested it out on my robot's onboard batteries
and power supplies, and it works great.

I uploaded a sample of the output to my webpage:
http://members.home.net/daniel.herrington/vital_signs.html

You can see how the battery voltages look a little smoother after I
added some capacitance to the VREF+ of the ADC.  Also, note the small
periodic fluctuations (every 30-45 minutes) in the +12V supply.  I
never would have noticed that before.  I'll have to investigate that.

Regards,
  Daniel Herrington

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=> Replying to Mike Loseke's message, "Re: [NCLUG] dynamic graph on web page" (Sep 22):
 > Thus spake Daniel Herrington:
 > > 
 > > NCLUGers,
 > > 
 > > Does anyone know of a canned linux solution (or not-canned) to create
 > > an up-to-date X-Y graph of some constantly changing data from a file
 > > and display it whenever someone clicks on a weblink?  I would like to
 > > be able to set up a little weather station and track the last 24 hour
 > > period on a web page.
 > > 
 > > I'm thinking I could write a perl script to output an xbm file, then
 > > run it through a converter and have the final image returned as a jpeg
 > > inside a dynamically-generated webpage, but I'd rather not re-invent
 > > the wheel if I can help it.
 > 
 >  I use rrdtool (http://ee-staff.ethz.ch/~oetiker/webtools/rrdtool/)
 > to do just exactly this with network traffic for a metric buttload of
 > WAN and LAN links. The distro includes a perl module and the website
 > has extensive documentation and examples to help out. rrdtool is going
 > to be what mrtg3 will be built on - if it ever comes out...
 > 
 >  For my stuff, I'm using perl and SNMP.pm to query routers and switches
 > for in/out octets then the rrdtool module to update it's little databases
 > (one per interface for my setup). I then have a cgi that allows a user
 > to select the link they want to see stats on and they are presented with
 > current stats (generated also using perl and rrdtool) with the option to
 > see several sets of historical data. Very very nice. It uses GD (I think)
 > to output either gif or png.
 > 
 > -- 
 >    Mike Loseke    | One of life's best joys is putting the little 
 >  mike at verinet.com | rubber feet on a new piece of networking gear.
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