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Thread: TI-74 Basic programs?

  1. Default

    Heat Index, 7-3-19

    Summer is here. Since temperature and humidity will vary from location to location, I decided to make a Heat Index program for my Ti-74 that I could use as I'm traveling and camping. I found this heat index formula,

    https://www.weather.gov/media/epz/wxcalc/heatIndex.pdf

    I also found a chart of temperature/humidity heat index values,

    https://www.weather.gov/safety/heat-index

    According to the chart, the temperature and humidity inputs need to be in a certain range to yield proper results. The temperature also needs to be in degrees fahrenheit and the relative humidity needs to be in percent. The output is a temperature in degrees fahrenheit of what the input temperature and humidity combined would seem to feel like.

    Check results to the chart to be sure the program is working properly. If the answer seems unusual, check it to the chart. The only limit is on the range of the heat index output value. It seems to work okay but remember, I'm no programmer or math expert.


    Code:
    700 PRINT "Heat Index":PAUSE .6
    710 PRINT T;"temp,deg f ";:ACCEPT NULL(T),T
    720 PRINT RH;"relative humidity,% ";:ACCEPT NULL(RH),RH
    730 A1=-42.379+(2.04901523*T):A2=(10.14333127*RH)
    740 A3=(0.22475541*T*RH):A4=(6.83782*10^-3*T^2)
    750 A5=(5.481717*10^-2*RH^2):A6=(1.2287*10^-3*T^2*RH)
    760 A7=(8.5282*10^-4*T*RH^2):A8=(1.99*10^-6*T^2*RH^2)
    
    770 ANS=A1+A2-A3-A4-A5+A6+A7-A8
    780 IF ANS>137 OR ANS<80 THEN PRINT "error..inputs out of range":PAUSE:GOTO 710
    790 PRINT USING"ans Heat Index,deg f=####.#";ANS:PAUSE:GOTO 700

    Example:

    0 temp,deg f 94
    0 relative humidity,% 70
    ans Heat Index,deg f= 119.0

    94 temp,deg f 90
    70 relative humidity,% 65
    ans Heat Index,deg f= 102.6

  2. #32

    Default

    Parabola, 8-20-19

    I have some left-over thin aluminum roofing flashing. I want to see if I can make a parabolic solar cooker that would grill a hamburger. I need to figure and trace out 1/2 of a parabolic curve for a cardboard template I'll use to trace the curve for the vertical aluminum ribs. I went online for a parabolic calculator but found them a little confusing. So I found a formula and made a program for my ti74. Check the ti74's output to an online calculator.

    After punching in some numbers, I decided to make the dish/reflector 6 feet in diameter and 18 inches high/deep. This should put the focus even with the outer edge of the reflector so I can easily mount a support across the dish at the focal point for the grill. I haven't built it but I'm hoping it will generate enough heat at the focal point to cook a hamburger using the sun. Cool if it did. (I must remember to wear good eye protection if I build and use it.)

    (enter 0 at 'increment (x)' to start over)


    Code:
    900 PRINT "Parabola":PAUSE .6
    910 INPUT "radius (x) ";R9,"height (y) ";T9:C9=T9/R9^2
    920 Z9=R9^2/(4*T9):PRINT "focus=";Z9:PAUSE
    925 INPUT "increment (x) ? ";K9:I9=K9^2*C9:IF K9<=0 THEN 900
    930 IF K9>R9 THEN PRINT "max incremented (x)=";R9:PAUSE:GOTO 925
    940 PRINT USING"INCREMENT (y)=###.###";I9;:PRINT " @";K9;"(x)":PAUSE:GOTO 925

    My planned dish example:

    radius (x) 36"
    height (y) 18"
    focus= 18"

    increment (x) then INCREMENT (y)

    1" = .014"
    2" = .056"
    3" = .125"
    4" = .222"
    5" = .347"
    6" = .500"
    7" = .680"
    8" = .889"
    9" = 1.125"
    10" = 1.389"
    11" = 1.681"
    12" = 2.000"
    13" = 2.347"
    14" = 2.722"
    15" = 3.125"
    16" = 3.556"
    17" = 4.014"
    18" = 4.500"
    19" = 5.014"
    20" = 5.556"
    21" = 6.125"
    22" = 6.722"
    23" = 7.347"
    24" = 8.000"
    25" = 8.681"
    26" = 9.389"
    27" = 10.125"
    28" = 10.889"
    29" = 11.681"
    30" = 12.500"
    31" = 13.347"
    32" = 14.222"
    33" = 15.125"
    34" = 16.056"
    35" = 17.014"
    36" = 18.000"
    Last edited by thumbs; August 20th, 2019 at 01:43 PM.

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