The Museum of HP Calculators

Resistors in Series or Parallel for the HP-33E/C

This program is Copyright © 1978 by Hewlett-Packard and is used here by permission. This program was originally published in "HP-33E Student Engineering Applications".

This program is supplied without representation or warranty of any kind. Hewlett-Packard Company and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.

Overview

This program calculates the total resistance of a group of resistors arranged in parallel or in series.

Formulas used: 

Resisters in series: RT = R1 + R2 + R3 ... + Rn
Resisters in parallel: RT = 1/(1/R1 + 1/R2 + 1/R3 ... + 1/Rn)

Note that this program can be used for summing capacitors in parallel or series instead of resisters. For series capacitors, use the instruction for parallel resistors. For parallel capacitors, use the instructions for series resisters.

Several more advanced programs for circuit analysis may be found in: Anderson, L.H. "Calculator-Aided Circuit Analysis," Ham Radio Magazine, pp. 38-46, October 1977. Although written for the HP-25, they will work equally well on the HP-33E/C.

Instructions

Step Instructions Input Data/Units Keys Output Data/Units
1 Enter program      
2 Initialize   f REG f PRGM  
3 a) Set for parallel resistors or   R/S 0.0000
  b) Set for series resistors   GSB 03 1.0000
4 Optional: Retrieve last RT for use in next calculation.   R↓ Previous RT  
5 Input individual resistor values (Repeat until all resistors have been input.) Ri R/S  
6 Calculate total resistance of the group     GSB 12 RT, ohms
7 Optional: Store RT for use in next calculation   RT STO 2  
8 Go to step 3a or 3b for next group.      

Example

Determine the total resistance from A to B.

Keystrokes          Display       Comment
f REG f PRGM
Group 1: R/S        0.0000        Parallel mode
680 R/S 120 R/S
GSB 12              102.0000      R1, ohms
Group 2: GSB 03     1.0000        Series mode
R↓                  102.0000      Retrieve R1
R/S 330 R/S
680 R/S
GSB 12              1,112.0000    R2, ohms
Group 3: R/S        0.0000        Parallel mode
R↓                  1,112.0000    Retrieve R2
R/S 220 R/S
GSB 12              183.6637      R3, ohms
STO 2                             Save R3
Group 4: R/S        0.0000        Parallel mode
680 R/S 470 R/S
GSB 12              277.9130      R4, ohms
         (Total R)
GSB 03              1.0000        Series mode
R↓                  277.9130      Retrieve R4
R/S RCL 2 R/S
GSB 12              461.5767      RT, ohms

The Program

LINE    CODE    KEYS
 00             f CLEAR PRGM
 01         0   0
 02     13 04   GTO 04
 03         1   1
 04     23  0   STO 0
 05        74   R/S
 06     24  0   RCL 0
 07     15 71   g X=0
 08     12 20   GSB 20
 09        22   R↓     
 10  23 51  1   STO + 1
 11     13 05   GTO 05
 12     24  1   RCL 1
 13     24  0   RCL 0
 14     15 71   g X=0
 15     12 20   GSB 20
 16        34   CLx
 17     23  1   STO 1
 18        22   R↓     
 19     13 00   GTO 00
 20        22   R↓     
 21     15  3   g 1/x
 22        31   ENTER↑
 23     15 12   g RTN

Register Use

R0  Code: 0 or 1
R1  ΣR, Σ1/R

Go back to the software library
Go back to the main exhibit hall