Sharp EL-5500 III Programing

[windryder06]

Hello all,

I am new to this site and looking for some help. I have a Sharp EL-5500 III Scientific Computer that I have had since it was new in 1988. I have used the calculator daily since then. Today I changed batteries in the unit and POOF all my programs from the past 21+ years are gone. The one that I used the most was for loan payments. Can anyone help me with a simple BASIC loan payment program for this computer?

This is what it asked:

LOAN PAYMENT

Loan Amount?

Interest Rate?

Number of Payments?

and then it gave the payment.

I never was any good at programming and any that I learned in BASIC are gone from my brain.

An help would be greatly appreciated.

Thank you,
Chris

 

[hmbrew]

Aside from writing new programs for it, I would be concerned about the memory backup battery. If I'm not mistaken, it's supposed to keep it from "forgetting" while the main batteries are out.

If that backup battery has failed, it might be worth replacing before you re-program everything. It might be soldered in, but it would be simple to install a battery holder for easier replacement in another 21 years.

 

[windryder06]

hmbrew,

Thanks for the reply, it is great info. I will take a look inside again for another battery.

Chris

 

[windryder06]

OK, where can I find that battery? I am assuming it is the thing that has the two leads attached to the board and attached to the inside cover...

 

[hmbrew]

Also, I would like more info.

1. Is it "simple" or "compound" interest?

2. If it is "compound", is it compounded continuously, or is it compounded on each payment?

The way I envision this program, it can be classified into 3 sections:

1:get all the input
2: Calculate the total amount after interest using the data you inputted
3: Divide step 2 by the number of payments, and tell you the final result.

Edit: are you sure it didn't ask the user about time? (ie:how long until it would need to be completely paid off, or how much time each payment is separated by?)
If it didn't ask those things, what might it have used by default? What values were used in the calculations you used it for?

Edit again: The battery is probably under another cover on the casing. If you can't easily see where it is, do some research or look in a manual rather than risk damaging the board.

 

[windryder06]

Simple is what it was...

How many volts should the back up battery have? Mine is showing .5 volts

 

[hmbrew]

I have no idea. All I can find is that it's main power came from a pair of small CR2032 batteries.

Is there a number listed on the backup battery you found? It should have ratings listed online somewhere.

As for the formula:

I=PRT

Where I= The total amount of interest gained over time
P= The initial amount of money
R= the interest rate
T= The time over which the interest is calculated.

I don't understand how it could have worked without the time variable. I need to know what value it used, if this is indeed the correct formula.

 

[gedgross]

I have the same model Sharp that I bought in Dec. 1986. The manual says that the memory is lost when you change the batteries. There is no mention of a back up battery. I will TRY to copy the mortgage program and send it to you.

 

[gedgross]

I am still trying to figure how to send you the mortgage program, but I found it in one of the manuals that came with the computer. It is in the "Computing the Sciences" manual on page 78.

 

[hmbrew]

I have the same model Sharp that I bought in Dec. 1986. The manual says that the memory is lost when you change the batteries. There is no mention of a back up battery. I will TRY to copy the mortgage program and send it to you.

Okay, thanks for clarifying. I had expected that there would be several battery changes over the course of 21 years, and apparently he has had the program that long. Therefore, I thought that it must have some sort of battery backup feature.

I would also be interested in seeing this program, as long as it wouldn't mean much extra work for you.

 

[PC Doctor]

The Answer

The Answer

INPUT "T/n, N, P, I = ", TN, N, P, I: I = I / 1200
IF N = 0 THEN PRINT "N="; -LOG(-I * TN / P + 1) / LOG(1 + I): RUN
IF P = 0 THEN PRINT "P="; -TN * I / ((1 + I) ^ -N - 1): RUN
N = N + TN * (TN <> 0): PRINT "T="; -P / I * ((1 + I) ^ -N - 1): RUN

This is a 4 line compressed program.
I wrote for myself to be quick and let me try things.
Unfortunately only I knew how to use it.
Now I've got to figure it out so I can explain it....... be right back .
.
.
.
I seem to remember that you put a zero in for the thing you want to solve.
(but never for I). hit break to stop it (it runs over and over to let you try things)

T/n = Total Principal (or payment n of N, more on this later)
N = Number of months (10 year=120)
P = Payment amount (monthly payment)
I = Interest (5% = 5)

so for a loan of $18,000
for 10 years (N=10*12)
at 5%
you would enter 18000,120,0,5
and it would say P=190.91........ (the payment amount)

so if you only wanted to pay $150
you'd enter 18000,0,150,5
and it would say N=166.7 (months, or about a 14 year loan)

if you want to see how much you can borrow for 10 years with $150 payments
enter 0,120,150,5
and it says T=14142 (total principal)

I've also got it rigged so that if you want to know how much you owe after payment
119 of 120 at $150 and 5%
you enter 119,120,150,5
and it says T=149.37.... (which would be 1 payment of 150 after 1 month int.)

 

[PC Doctor]

PS: I need an el-5500 (III preferably)

 

[PC Doctor]

I just got an el-5500III and that program I put up, doesn't work the same on it (i think fbasic makes true -1)
so, I rewrote it for the EL-5500 and here it is....

111 INPUT "LOAN AMOUNT = ";TN
120 INPUT "# MO. PAYMENTS = ";N
130 INPUT "PAYMENT AMOUNT = ";P
140 INPUT "INTEREST RATE = ";I
150 IF N=0 THEN PRINT "# MO. PAYMENTS = ";-LOG(-I/1200*TN/P+1)/LOG(1+I/1200): GOTO 111
160 IF P=0 THEN PRINT "PAYMENT AMOUNT = ";-TN*I/1200/((1+I/1200)^-N-1): GOTO 111
170 N=N-TN*(TN<>0)RINT "LOAN AMOUNT = ";-P/I*1200*((1+I/1200)^-N-1): GOTO 111

note the variables never change, so you can go back through the inputs a second time entering nothing except the one value you want to try changing to get a new answer