1. Member
Join Date
Jan 2018
Posts
38
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. Member
Join Date
Jan 2018
Posts
38
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:

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.

3. Member
Join Date
Jan 2018
Posts
38
Combined Gas Law, 11-4-19

On one of my old cars I want to increase the pressure in my copper radiator and raise the boiling point of the coolant. Using water as the coolant, what temperature would my coolant boil with a 16 psi radiator cap instead of my current 15 psi cap? I wanted the answer in customary English units of which I'm most familiar. I found this Combined Gas Law calculator online....

https://www.calcprofi.com/combined-g...alculator.html

I made a program for my Ti74. (I don't always have access to wifi and my phone is 'dumb') The program yields similar results to the online calculator. If I'm understanding and calculating correctly, going from a 15 psi cap at a 212 deg f boiling point to a 16 psi cap should yield a boiling temp of 257 deg f. I'm no math expert or programmer so check the results for yourself. But I think I'll give a 16 psi cap a try.

Code:
```1100 PRINT "Combined Gas Law":PAUSE .8
1105 PRINT "Enter 0 For":PAUSE .8
1107 PRINT "Desired Quanity":PAUSE .8
1110 PRINT A;"> V1,in3 ";:ACCEPT NULL(A),A:V1=A
1120 PRINT B;"> P1,psi ";:ACCEPT NULL(B),B:P1=B
1130 PRINT C;"> T1,deg f ";:ACCEPT NULL(C),C:T1=C+459.67
1140 PRINT D;"> V2,in3 ";:ACCEPT NULL(D),D:V2=D
1150 PRINT E;"> P2,psi ";:ACCEPT NULL(E),E:P2=E
1160 PRINT F;"> T2,deg f ";:ACCEPT NULL(F),F:T2=F+459.67

1170 IF A=0 THEN X=(V2*P2*T1)/(P1*T2):X\$="V1,in3=":A=X:GOTO 1240
1180 IF B=0 THEN X=(V2*P2*T1)/(V1*T2):X\$="P1,psi=":B=X:GOTO 1240
1190 IF C=0 THEN X=(V1*P1*T2)/(V2*P2):X=X-459.67:X\$="T1,deg f=":C=X:GOTO 1240
1200 IF D=0 THEN X=(V1*P1*T2)/(P2*T1):X\$="V2,in3=":D=X:GOTO 1240
1210 IF E=0 THEN X=(V1*P1*T2)/(V2*T1):X\$="P2,psi=":E=X:GOTO 1240
1220 IF F=0 THEN X=(V2*P2*T1)/(V1*P1):X=X-459.67:X\$="T2,deg f=":F=X:GOTO 1240
1230 PRINT "error..":PAUSE:GOTO 1100

1240 ANS=X:PRINT "ans ";X\$;X:PAUSE:GOTO 1100```

V1=1 in3 [enter]
P1=15 psi [enter]
T1=212 deg f [enter]

V2=1 in3 [enter]
P2=16 psi [enter]
T2=0 [enter]

T2=256.778 deg f

4. Member
Join Date
Jan 2018
Posts
38
Stat, 12-15-19

My granddaughter was showing me how to use/do paired statistics. She had her TI-84 and I had my TI-74 in Calc Mode trying to keep up with her. In Calc Mode I haven't found a way to view entered data. But unlike variables in Basic Mode, Calc Mode stores the stat data with the TI-74 off. In Basic Mode the Basic programm is saved with the TI-74 off.

In the TI-74 User's Guide, TI gives the stat formulas and a spring example using paired data. I thought if I were to store paired data in Basic DATA statements in a program my paired data would be stored and more easily edited. Using TI's stat formulas I wrote a Basic program to do stats. The program yields the same results for TI's spring example as calculated in the Calc Mode using the [stat] keys. How many lines of DATA statements before you're out of memory or it errors itself out, I don't know. I allowed almost 500 program lines for the paired data.

Like I say, I'm no math expect or programmer so check it out for yourself. The program is intended for use with paired data. I'm going to get my granddaughter to show me a few more things now that I can view, edit and enter data more easily.

Code:
```1 DATA 27,99
2 DATA 32,152
3 DATA 23,81
4 DATA 25,98
5 DATA 31,151
6 DATA 28,112

499 DATA 1.E+126,1.E+126

500 ON ERROR 810:RESTORE:X=0:Y=0:N=0:SUMX=0:SUMY=0
503 MEANX=0:MEANY=0:SUMX2=0:SUMY2=0:SUMXY=0
510 IF X=1.E+126 AND Y=1.E+126 THEN 580
520 SUMX=X+SUMX:SUMY=Y+SUMY
530 MEANX=SUMX/N:MEANY=SUMY/N
540 SUMX2=SUMX2+X^2:SUMY2=SUMY2+Y^2
550 SUMXY=SUMXY+(X*Y)
570 GOTO 505

580 PRINT :PRINT "sumx =";SUMX:PAUSE
590 PRINT "sumy =";SUMY:PAUSE
600 PRINT "meanx =";MEANX:PAUSE
610 PRINT "meany =";MEANY:PAUSE
620 PRINT "sumx2 =";SUMX2:PAUSE
630 PRINT "sumy2 =";SUMY2:PAUSE
640 PRINT "sumxy =";SUMXY:PAUSE

650 A=(SUMX*(((SUMX*SUMY)/(N-1))-SUMXY))/(((N-1)*SUMX2)-SUMX^2)+(SUMY/(N-1))
660 PRINT "A intercept =";A:PAUSE
670 B=(((N-1)*SUMXY)-(SUMX*SUMY))/(((N-1)*SUMX2)-SUMX^2)
680 PRINT "B slope =";B:PAUSE
690 SX=((((N-1)*SUMX2)-SUMX^2)/((N-1)*((N-1)-1))):SX=SQR(ABS(SX))
700 SY=((((N-1)*SUMY2)-SUMY^2)/((N-1)*((N-1)-1))):SY=SQR(ABS(SY)):R=(B*SX)/SY

710 PRINT "R cor coef =";R:PAUSE
720 PRINT "SX =";SX:PAUSE
730 PRINT "SY =";SY:PAUSE
740 PRINT "N =";N-1:N=N-1:PAUSE

770 INPUT "est x or y  ";Z\$:IF Z\$="x"THEN 790
780 IF Z\$="y"THEN 800 ELSE 500
790 INPUT "est,x enter y  ";Y:X=(Y-A)/B:PRINT "est x =";X:PAUSE:GOTO 770
800 INPUT "est,y enter x  ";X:Y=A+(B*X):PRINT "est y =";Y:PAUSE:GOTO 770

810 PRINT "Error..redo":PAUSE:END```

Example: enter paired data into program DATA statements starting with line number 1

1 DATA 27,99
2 DATA 32,152
3 DATA 23,81
4 DATA 25,98
5 DATA 31,151
6 DATA 28,112

now RUN, use [enter] to toggle through the results

sumx = 166
sumy = 693
meanx = 27.66666667
meany = 115.5
sumx2 = 4652
sumy2 = 84415
sumxy = 19667
A intercept = -114.8483146
B slope = 8.325842697
R cor coef = .9697571933
SX = 3.444802849
SY = 29.57532756
N = 6

estimate x, (enter y) 84.97191011
est x= 24

estimate y, (enter x) 24
est y= 84.97191011
Last edited by thumbs; December 15th, 2019 at 05:49 AM.

5. Member
Join Date
Jan 2018
Posts
38
Stat, 12-15-19 Edit:

I can only edit a short time after I post. I was looking over the Stat program and I see I was a little redundant. You can reduce the repetitive math by replacing these lines if you want. Stat should operate the same and yield the same results.

580 N=N-1:PRINT :PRINT "sumx =";SUMX:PAUSE

650 A=(SUMX*(((SUMX*SUMY)/N)-SUMXY))/((N*SUMX2)-SUMX^2)+(SUMY/N)

670 B=((N*SUMXY)-(SUMX*SUMY))/((N*SUMX2)-SUMX^2)

690 SX=(((N*SUMX2)-SUMX^2)/(N*(N-1))):SX=SQR(ABS(SX))

700 SY=(((N*SUMY2)-SUMY^2)/(N*(N-1))):SY=SQR(ABS(SY)):R=(B*SX)/SY

740 PRINT "N =";N:PAUSE
Last edited by thumbs; December 15th, 2019 at 02:04 PM.

6. Member
Join Date
Jan 2018
Posts
38
Ohm DC, 1-22-2020

I wanted to be able to work a list of formulas directly. I put the formulas in DATA statements. With the [+] [-] keys I can scroll up and down the formula list. When I find a formula I want, I break the program and do [SHIFT] [PB]. I store the formula holding [FN] and [SHIFT] then [1]. I seed the variables, recall the formula with [FN] [1] then [ENTER] the formula and look at the variable result.

Sometimes I seed the variables in the DATA statement followed by the formula and a PRINT statement. I break the program, recall with [SHIFT] [PB] then [ENTER] the formula for the result. In the program below I include some Ohms Law DC formulas I use. Here's a webite that has more formulas.

http://www.electrical101.com/ohms-law.html

I find this quicker and easier than writing seperate small programs or typing everything in repeatedly. I'm no programmer or math expert, so check everything out before using.

E=voltage,volts
I=currect,amps
R=resistance,ohms
P=power,watts

Code:
```1 DATA Ohm DC..use + - keys
2 DATA E=12:R=2:I=E/R:PRINT I
3 DATA I=SQR(P/R)
4 DATA I=P/E
5 DATA R=E/I
6 DATA R=P/I^2
7 DATA R=E^2/P
8 DATA E=I*R
9 DATA E=P/I

99 DATA end..

100 C9=0:DIM A9\$(105)
120 IF A9\$(C9)="end.."THEN 200
130 GOTO 110

200 C9=0
210 C9=C9+1:PRINT A9\$(C9):IF A9\$(C9)="end.."THEN 230
220 IF KEY\$="+"THEN C9=C9+1:PRINT A9\$(C9)
225 IF C9>98 THEN C9=99
230 IF KEY\$="-"THEN C9=C9-1:PRINT A9\$(C9):IF C9<2 THEN C9=0 ELSE 230
240 IF A9\$(C9)="end.."THEN C9=C9-1:GOTO 230
250 GOTO 210```

Examples: E=12 R=2 I=6

[RUN] [ENTER] [+]

E=I*R [BREAK] [CLR] [SHIFT] [PB]

E=I*R [FN]and[SHIFT] [1]

I=6 [ENTER]
R=2 [ENTER]
[FN] [1] E=I*R [ENTER]

E [ENTER] 12

..................................

[RUN] [ENTER] [+]

E=12:R=2:I=E/R:PRINT I [BREAK] [CLR]

[SHIFT] [PB] E=12:R=2:I=E/R:PRINT I

[ENTER] 6
Last edited by thumbs; January 22nd, 2020 at 05:47 PM.

7. Member
Join Date
Jan 2018
Posts
38
Vectors, 2-20-20

I could find a single magnitude and angle using [P>R] in calc mode. I wrote this program to find the resultant of a number of vectors. All angles are in degrees decimal (dd). On a quadrant, angles are positive rotating counter-clock-wise (CCW) 0 to 359 degrees. 'resang-360' shows the resultant angle negative from 0 rotating in the clock-wise (CW) direction.

I went online to find examples of vector addition and the resultant. There are many websites explaining the process. Here are two with worked examples and a third with example and calculator. The Vectors program seems to give similar results. [spc] bar at the end repeats the answer and [enter] returns to the beginning. Re-RUN to clear.

https://www.ae.msstate.edu/vlsm/forc...s/example1.htm

http://hyperphysics.phy-astr.gsu.edu/hbase/vect.html

I'm no math expert or programmer so check the program out completely for yourself. I might have missed something or there could be thing's of which I'm unaware.

Code:
```6000 PRINT "Vectors":PAUSE .6:DEG
6002 PRINT "..all angles deg dec":PAUSE 1.2
6005 VA=0:VB=0:PRINT X;"# of vectors ";:ACCEPT NULL(V),V
6006 IF V=0 THEN V=X ELSE X=V
6008 IF V>9 OR V<2 THEN PRINT "error..2 to 9":PAUSE:GOTO 6005
6010 PRINT M9(V);"#";V;"mag ";:ACCEPT NULL(M9(V)),M9(V)
6012 PRINT N9(V);"#";V;"dd ";:ACCEPT NULL(N9(V)),N9(V)
6015 IF N9(V)<0 THEN N9(V)=N9(V)+360
6020 IF V=1 THEN 6100 ELSE V=V-1:GOTO 6010

6100 V=X:PRINT"..."
6110 A=SIN(N9(V)):SA(V)=M9(V)*A:A=COS(N9(V)):SB(V)=M9(V)*A
6120 VA=VA+SA(V):VB=VB+SB(V):V=V-1:IF V=0 THEN 6200
6130 GOTO 6110

6200 F=ATN(VA/VB):E=VB/COS(F):E=ABS(E)
6210 IF VA>0 AND VB<0 THEN F=180+F
6220 IF VA<0 AND VB<0 THEN F=180+F
6230 IF VA<0 AND VB>0 THEN F=360+F
6235 RESMAG=E:RESANG=F
6240 PRINT "resmag= ";E;"mag":PAUSE:PRINT "resang= ";F;"dd":PAUSE
6250 PRINT "resang-360= ";RESANG-360;:PRINT "dd":PAUSE
6260 PRINT "[spc] or [enter]":IF KEY\$=" "THEN 6240 ELSE 6005```

Example 1, with the boat example:

0 # of vectors, 2
0 # 2 mag, 15000 N
0 # 2 dd, 30 dd
0 # 1 mag, 20000 N
0 # 1 dd, -50 dd

resmag= 27003.49804 N
resang= 343.1644917 dd
resang-360= -16.8355083 dd

(from 0 dd, 343.1644917 CCW same as -16.8355083 CW)

...........................

Example 2, with the series RLC circuit:

0 # of vectors, 3
0 # 3 mag, 245.04 ohm
0 # 3 dd, 90 dd
0 # 2 mag, 250 ohm
0 # 2 dd, 0 dd
0 # 1 mag, 1.7684E3 ohm
0 # 1 dd, -90 dd

resmag= 1543.737571 ohm
resang= 279.3197872 dd
resang-360= -80.68021281 dd

..........................

Example 3, 4 vectors with the online calculator:

0 # of vectors, 4
0 # 4 mag, 120
0 # 4 dd, 160
0 # 3 mag, 110
0 # 3 dd, 225
0 # 2 mag, 140
0 # 2 dd, 260
0 # 1 mag, 120
0 # 1 dd, 340

resmag= 238.5998386 mag
resang= 244.6668012 dd
resang-360= -115.3331988 dd

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