Ryan,
Some comments from the peanut gallery. I've built a few large setups,
data/colo, networking and video production. I never counted racks, so I
guess that means they had a bunch. For us everything was driven of mean
power per volume. Everything else came and went, but changing that took
serious work (especially the cooling.)
When you talk about a few hundred sensors, everything becomes a bit more
serious. You are completely correct you don't want to solder cables, but
you are going to have to bring it all together yourself. That's the trade
off for getting dirt cheap sensors.
First some general comments: I would definitely use +5 power and
simultaneous reads. For me it's about making the controls a bit more
stable. Even at 50-100 sensors per bus, I just think it's easier this way.
If I was attacking this, I would start by designing a simple PC board that
gets RJ45 connectors and places to mount the sensors. Then a tech wires up
the boards. I would design the board so wiring could be done in 3 ways,
true daisy chain, star wired cat5e with sequential data bus (see my recent
postings about this) and 4 wire pass through (an extension of the star/bus
design.) Then use jumpers to set up the way it works in any given location.
All of the wires are just 8 wire RJ45s on the sensor end. On the daisy
chain and pass through, the other end is also RJ45, in the star/bus they
come to blocks. To keep lengths to a minimum, I would have local clusters
that can have racks and such easily added and removed. I would also leave
room on the board to have humidity sensors or other 1-wire capabilities.
In my mind's eye, this seems relatively easy to get all the data collected.
I have some single board linux computers that I am happy with. I run
owserver on these, then gather all the buses together with a parent machine.
I would not use RRD or anything like that to handle the data directly. At a
dollar per GB, why not keep all the sensor data forever? Then use alarm
tools, RRD and the like working against the data store. You never know what
question you might want to ask tomorrow, and without raw data you lose that
ability. All you need to capture is the sensor id, type, value and sample
time. Given the research flavor of the site, this seems quite reasonable.
Hope this rambling was of some help.
jerry
Jerry Scharf
laguna way consulting
-------------------------------------------------------
This SF.Net email is sponsored by: NEC IT Guy Games. How far can you shotput
a projector? How fast can you ride your desk chair down the office luge track?
If you want to score the big prize, get to know the little guy.
Play to win an NEC 61" plasma display: http://www.necitguy.com/?r=20
_______________________________________________
Owfs-developers mailing list
Owfs-developers@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/owfs-developers
