DPRG mailing list archives: [DPRG] Re: Rs-232 Thermometer

Wed Dec 19 13:28:44 CST 2007

Obviously, you added enough sensors for your robot to become sentient.
Therefore, I believe the simplest explanation is that this particular is
being happens to be nocturnal, hence the heavy nighttime activity and the
lull during the day.

Of course, someone with an actual ME degree might suggest that something is
causing 'short cycling' in the AC system (a lack of hysteresis in the
controller perhaps), leading to the graph you see. But, alas, I was a CS
guy, so I don't really know, but I remember seeing a graph like that on a
friend's HVAC project... ;-)

---
Dave

On Dec 18, 2007 2:37 PM, dpa <dpa at io.isem.smu.edu> wrote:

> Howdy,
>
> Thanks for all the input and pointers.
>
> I ended up buying a SensaTronics IT Model F with a single
> temperature probe (it can handle 2) which is now underneath
> the raised floor in the data center.
>
> A bit of perl and a serial cable provided readings at one
> minute intervals starting at 12:30pm yesterday.   Here's
> what it recorded:
>
> <http://www.geology.smu.edu/~dpa-www/gif/temperature_log.png<http://www.geology.smu.edu/%7Edpa-www/gif/temperature_log.png>
> >
>
> If we have any air conditioning guru's on the list, care to
> comment on what this all means?
>
> The graph y axis is degrees F and X axis is minutes since 12:30
> yesterday.  The temp held steady at 70.5 degrees +- 0.1 degree
> until about 15:30, when I think the data center door was closed.
> The rise in temp starts at 18:30 and then enters a strange cycle
> between 63 and 76 degrees at 10 minute intervals with an odd
> retrograde bump in the middle of each cycle.  At about 8:00am
> this morning that cycle ended.  The graph is almost exactly
> 24 hours.
>
> (I though this appropriate posting since we're always talking
> about thermostats and whether or not they are "robots"  ;)
>
> best,
> dpa
>
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