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#1
Posted to alt.solar.thermal,alt.energy.homepower,alt.energy.renewable,alt.home.repair
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Home automation controllers
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 = $115 from http://www.ewayco.com/51-embedded-sy...ed-system.html It uses 15 watts. Is there a way to reduce the power, and does it have 256 or 512M flash memory? It also comes with a wireless option. A simple control using a few-$-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 http://www.aagelectronica.com/aag/in...tml&lang=en-us and a $27 DS9490R 1-wire adapter, with OWFS as a 1-wire driver, and an X10 interface, eg the $69 2414u from http://www.smarthome.com/2414u.html 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 http://www.x10.com/automation/am466_s.html http://www.hobby-boards.com/catalog/index.php?cPath=24 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.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor 210 HCF=12.1*SQR(VEL)'forced convection conductance 220 TAA=TA+273'air temp (K) 230 TRA=TR+273'mean radiant temp (K) 250 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp 260 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermed iate values 300 P5=308.7-.028*MW+P2*(TRA/100)^4 310 XN=TCLA/100 320 XF=XN 330 N=0'number of iterations 340 EPS=.00015'stop iteration when met 350 XF=(XF+XN)/2'natural convection conductance 360 HCN=2.38*ABS(100*XF-TAA)^.25 370 IF HCFHCN THEN HC=HCF ELSE HC=HCN 380 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC) 390 N=N+1 400 IF N150 GOTO 550 410 IF ABS(XN-XF)EPS GOTO 350 420 TCL=100*XN-273'clothing surface temp (C) 440 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin 450 IF MW58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating 460 HL3=.000017*M*(5867-PA)'latent respiration heat loss 470 HL4=.0014*M*(34-TA)'dry respiration heat loss 480 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation 490 HL6=FCL*HC*(TCL-TA)'heat loss by convection 510 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient 520 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote 530 PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied 540 GOTO 580 550 PMV=99999!:PPD=100 580 PRINT TA,RH,CLO,PMV,PPD 19.6 86 1 -.4778556 9.769089 After removing the comments with something like sed "s/'.*//;" gwfile.bas bwfile.bas and adding back 'THEN's which bw complained were out of spec, eg in 410 IF ABS(XN-XF)EPS GOTO 350 we got 19.6 86 1 -0.4778564 9.7691115 which seems close enough :-) Nick |
#3
Posted to alt.solar.thermal,alt.energy.homepower,alt.energy.renewable,alt.home.repair
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Home automation controllers
Anthony Matonak wrote:
Nathan and I have settled on a mini-pc for a smart whole house fan controller ... http://www.ewayco.com/51-embedded-sy...ed-system.html 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. Have you considered one of the gumstix computers? We just looked at that. No USB port? ... 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. Sounds good. I wonder if we can store everything in the TU flash and power down the power supply 99% of the time. http://docwiki.gumstix.org/Frequentl...Heat_and_power Then again, how fast a computer do you need for this kind of stuff? A 60 Hz Turing machine might work :-) Have you considered a PDA? They come with their own display and are pretty thrifty with the power requirements. That's sorta where we started. 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. 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 |
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