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 = $115 from
A simple control using a few-$-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
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