Re: Looking for Temp and humidity sensors

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" wrote:

<stuff snipped>

> The Bobcat temperature node includes a power supply, an RS485 interface,
an
> ADC chip (I think they use a PIC but it's been a while since I looked
inside
> one), an enclosure and an LM34 temperature sensor.
>
> The Bobcat humidity node includes all of the above but with a Humirel
> humidity sensor replacing the LM34. Humidity sensors are not cheap.

Too bad.  I see other topologies like Phil Anderson's that make me believe
the Bobcats could either be made more functional or less expensive, overall,
but I suppose for limited uses where the sensor needs to be bulletproof and
highly reliable, the Bobcats make sense.  With 16 port Ethernet hubs going
for less than $50 I would have thought we would have seen more things
appearing more quickly for networking like remote temperature sensing and
even electrical load control.


> If you try to duplicate the design you will find that you really cannot
> build them and sell them through distribution channels for much less than
> what ADI charges.

<sigh>  And economies of scale never amount to much in small operations like
ADI's so the price isn't likely to come down as manufacturing techniques
improve.  I wonder if HA will ever see a time where component prices drop
the way hard drive prices have for PC's?  X-10 seems to have come the
closest in lowering prices through high volume.  It's probably what make it
difficult for some people to jump to the next level - almost every other HA
control technology is at least double the cost of X-10.  That sets up a
mental expectation that it will also be twice as good.

> If you already have some type of controller with ADC inputs and a power
> supply and a little knowledge you can DIY and save (if you conveniently
> ignore the cost of the controller). The cheap sensors need something like
an
> SECU16 or other controller.

It doesn't seem that many people are interested in knowing the temps in each
room in the house.  I'm probably just a data freak but it seems to me a home
automation system HAS to know details like that to effectively conserve
energy.

> I think your plans are overkill but you should look at some of the
one-wire
> interfaces which allow you to network lots of relatively inexpensive
sensors
> (at least for temperature, RH is still not cheap). You still need some
type
> of controller or PC to make sense of the data.

I just want something simple that can log the temperatures and RH's of the
various sensors to an ASCII file that I can analyze later.  If I had the
technosmarts to crack the RF protocol of the RatShack remote
thermo/hygrometers (six units, three with RH, three without) and record that
output to a text file, I'd be happy.  But in reality, I'd like to monitor
three temps per room, at least (ceiling, floor and about 3' from the floor.
I don't need RH from each room, but I'd like it from critical rooms like the
bathrooms, the basement, the pantry, the attic and the kitchen.

Why so many sensors?  I believe it will be the foundation of a truly "smart"
home that can look for data anomalies and thus detect open windows, clogged
furnace filters, improperly operating dampers and a whole host of other
things.  A house is like a human being in that it tries to maintain a fairly
constant internal environment.  To do that, you have to have lots of sensory
input.

--
Bobby G.