Home automation controllers

[nicksanspam]

Christian Kaiser wrote re heliostat control:

... a PC is far too sophisticated for your job. Unless you need it switched >on anyway, it's a waste of energy.

Nathan and I have settled on a mini-pc for a smart whole house fan controller that turns off an AC and runs a fan when it's cooler outdoors, and turns off a heater and runs the fan when it's warmer outdoors and the air is dry enough so there's no chance of condensation:

TU System 128mb ram + 512mb flash + Desktop Linux = $115 from

It uses 15 watts. Is there a way to reduce the power, and does it have 256 or 512M flash memory? It also comes with a wireless option.

A simple control using a few-$-Atmel controller is much better...

We found Atmel BASIC constraining, altho your displays seem nice.

and uses only very extremely little energy. My brother designed me a small >system that reads the stoarge temps to be shown in the bathroom. The system >has two CPUs with two LCDs (one in the cellar, one in the bathroom) and uses >a total of 6 W, including one backlighted LCD. Now I see the energy stored >in our water storage, easy to see whether better to take a shower, or >whether a bath is possible ;-) > >I added some programing to show sunrise, sunset, azimuth angle, ... even the >percentage the moon is visible - just because the CPU was running anyway, >and I have lots of RAM (128 KB!) available. Such a simple system has >everything you would need - floating point support, a lot of I/O ports, ...

Does it have a Roman numeral arithmetic package? My first programming language did, with error messages like "wrong Roman constant."

We are planning to use 2 $44 TAI 8540A 1-wire RH & temp sensors from

a $27 DS9490R 1-wire adapter, with OWFS as a 1-wire driver, and an X10 interface, eg the $69 2414u from or Home Depot (are these too smart to program via linux?) with X10 controllers for an AC, a heater, 2 fans and a damper, eg $11 15 amp AM466s from has more fun stuff.

We are also looking at bwbasic, which appears to be about as old as gwbasic. Here's an ASHRAE 55-2004 comfort calc done both ways:

50 CLO = 1'clothing insulation (clo) 60 MET=1.1'metabolic rate (met) 70 WME=0'external work (met) 80 TA=19.6'air temp (C) 90 TR=19.6'mean radiant temp (C) 100 VEL=.1'air velocity 120 RH=86'relative humidity (%) 130 PA=0'water vapor pressure 140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa 150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa 160 ICL=.155*CLO'clothing resistance (m^2K/W) 170 M=MET*58.15'metabolic rate (W/m^2) 180 W=WME*58.15'external work in (W/m^2) 190 MW=M-W'internal heat production 200 IF ICL

[Anthony Matonak]

[e-mail] wrote: ...

Have you considered one of the gumstix computers? They may not be any cheaper but the base configuration gives you a couple of serial ports and only uses about half a watt, less when idle. They can run Linux and use CF memory.

Then again, how fast a computer do you need for this kind of stuff? Have you considered a PDA? They come with their own display and are pretty thrifty with the power requirements.

For that matter, you might even go so far back as the famous Radio Shack Model 100 which crops up on Ebay for $20 or so pretty regular. It only uses a watt or so and has basic built in. :)

Anthony

[nicksanspam]

We just looked at that. No USB port?

Sounds good. I wonder if we can store everything in the TU flash and power down the power supply 99% of the time.

A 60 Hz Turing machine might work :-)

That's sorta where we started.

Right... I bought one of those for engineering calcs when I worked for Control Data, over humongous objections :-) I have something older in my attic with cassette tape I/O.

Nick