HP 12C Platinum: RC Series Circuit Analysis

HP 12C Platinum: RC Series Circuit Analysis

The program was originally posted on the Museum of HP Calculators website (https://www.hpmuseum.org/forum/thread-24591-post-215436.html#pid215436).

A difference between the HP 12C Platinum and the HP 12C Classic is that the Platinum has a square function (x²). The square function is the g-shifted (blue) of the multiplication key.

Introduction and Program Code

Given the following of a RC series circuit:

Stack Z: E: voltage of the RC circuit

Stack Y: R: resistance of the resistor (R) in ohms (Ω)

Stack X: Xc: equivalent resistance of capacitor (Xc) in ohms (Ω)

What is calculated:

Stack Z: equivalent impedance of the RC series circuit in ohms (Ω), Z = √(R^2 + Xc^2)

Stack Y: current in amps (A), I = E ÷ Z

Stack X: true power in watts (W), P = I^2 * R

Program Code:

x^2	001	43, 20	beginning of the program
x<>y	002	34
STO 0	003	44, 0	store resistor
x^2	004	43, 20
+	005	40
√x	006	43, 21
PSE	007	43, 31	show impedance
ENTER	008	36
R↓	009	33
÷	010	10
PSE	011	43, 31	show current
ENTER	012	36
x^2	013	43, 20
R↓	014	33	stack manipulation (014 – 018)
R↓	015	33
x<>y	016	34
R↓	017	33
R↓	018	33
RCL 0	019	45, 0
×	020	20
GTO 000	021	43, 33, 000	finish program, show power

Example

E = 150 V

R = 19 Ω

Xc = 10 Ω

Results (to four decimal places):

Z ≈ 21.4709 Ω

I ≈ 6.9862 A

P ≈ 927.3319 W

Source

Noll, Edward M. Basic Electronics Math With a Scientific Calculator Howard W. Sams & Co, Inc. Indianapolis, IN. 1977. 0-672-21425-3 pp. 81-98

Eddie

All original content copyright, © 2011-2026. Edward Shore. Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited. This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.

HP 20S: Triac Waveforms

HP 20S:   Triac Waveforms

Introduction

The following calculations involve triode AC switches, better known as triacs.  A triac is generally used as a bidirectional power switch device.  James J. Davidson, the original author of the HP 25 programs states "these programs are for use with mean-absolute (also called average) responding voltmeters which are calibrated to read the rms value of a sine wave"  (Davidson, 38).

The variables used in Davidson's programs are: 

Vs = root mean square from source

VLMS = root mean square voltage

VLMA = average load voltage

θ = firing angle of triac in degrees (Davidson, 38)

These programs have been translated to for the use of the HP 20S calculator.  

HP 20S Program:  Triac Waveforms

(59 steps)

Given:  Vs and θ°, calculate VLMA and VLMS

Store Vs in R0

Store θ° in R1 (degrees)

Press [ XEQ ] [ A ]

VLMA is displayed

Press [ R/S ], VLMA is displayed

Given:  Vs and VLMA, calculate θ° and VLMS

Store Vs in R0

Store VLMA in R4

Press [ XEQ ] [ B ]

θ° is displayed

Press [ R/S ], VLMA is displayed

Variables:

R0 = Vs

R1 = θ in degrees

R2 = θ in radians

R3 = VLMA 

R4 = VLMS

Program Code

Key Code:  { Key }

61, 41, A:  { LBL A }

61, 24:  { RAD }

22, 1:  { RCL 1 }

61, 55:  { →RAD }

21, 2:  { STO 2 }

24:  { COS }

75:  { + }

1:  { 1 }

74:  { = }

55: { × }

22, 0:  { RCL 0 }

45:  { ÷ }

2:  { 2 }

74:  { = }

21, 3:  { RCL 3 }

26:  { R/S }

51, 41, 1:  { GTO 1 }

61, 26:  { RTN }

61, 41, b:  { LBL B }

61, 24:  { RAD }

33:  { ( }

2:  { 2 }

55:  { × }

22, 3:  { RCL 3 }

45:  { ÷ }

22, 0:  { RCL 0 }

65:  { - }

1:  { 1 }

34:  { ) }

51, 24:  { ACOS }

21, 2:  { STO 2 }

51, 55:  { →DEG }

21, 1:  { STO 1 }

26:  { R/S }

51, 41, 1:  { GTO 1 }

61, 26:  { RTN }

61, 41, 1:  { LBL 1 }

61, 22:  { π }

65:  { - }

22, 2:  { RCL 2 }

75:  { + }

33:  { ( }

2:  { 2 }

55:  { ÷ }

22, 2:  { RCL 2 }

34:  { ) }

23:  { SIN }

45:  { ÷ }

2:  { 2 }

74:  { = }

11:  { √ }

55:  { × }

22, 0:  { RCL 0 }

45:  { ÷ }

61, 22:  { π }

11:  { √ }

74:  { = }

21, 4:  { STO 4 }

61, 26:  { RTN }

Example

Example 1:

Inputs:  θ  = 75° (stored in R1), Vs = 160 (stored in R0)

Results:

VLMA ≈ 100.70552

VLMS ≈ 130.27094

Example 2:

Inputs:  VLMA = 130 (stored in R3), Vs = 160 (stored in R0)

Results:

θ ≈ 51.31781°

VLMS ≈ 149.25534

Source

Davidson, James J.  "Triac Waveforms #1" and "Traic Waveforms #2" 65 Notes V3N10 December 1976.  pg. 38.  

All original content copyright, © 2011-2022.  Edward Shore.   Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited.  This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author and any authors of original programs and scripts.  

HP Prime and HP 42S: Noise Figure and Noise Voltage

HP Prime and HP 42S:  Noise Figure and Noise Voltage

Notes:  The programs for the HP 42S format are designed to work with the HP 42S's solver.  The programs were created using Thomas Okken's Free42, and should also be compatible with the Swiss Micros DM42.

Noise Figure

Given system temperature (in Kelvins), this program calculates the noise figure (in Decibels), which describes the noise performance of an amplifier.  The noise figure is described as the difference between the noise output of an actual receiver to an ideal, noiseless receiver.  A noiseless receiver is said to have a resistor operating at room temperature, 290 K (about 16.85°C or 62.33°F). The lower the noise figure, the better.

Formula:

F = 10 * log(T/290 + 1)

where:

F = noise figure (dB)
T = system temperature (K)

HP Prime Program Function:  NOISEDB

EXPORT NOISEDB(T)
BEGIN
// Noise Figure in dB
// Input: T: Temperature (K)
// 2019-01-04 EWS
10*LOG(T/290+1);
END;

HP 42S Program for Solver:  NSEFG

00 { 35-Byte Prgm }
01▸LBL "NSEFG"
02 MVAR "F"
03 MVAR "T"
04 RCL "T"
05 290
06 ÷
07 1
08 +
09 LOG
10 10
11 ×
12 RCL "F"
13 -
14 END

Example (Fix 4):

Input:  T = 57.8°F, convert it to Kelvins, enter 287.4833 K (approximately)
Result:  F = 2.9914 dB

Noise Voltage

Given the noise bandwidth (in Hertz) and the resistance (in Ω), calculate the open-circuit voltage (in RMS volts).

Formula:

e_n = √(1.6*10^-20 * B * R)

where:

e_n = open circuit voltage noise (RMS volts)
B = bandwidth (Hz)
R = resistance (Ω)

HP Prime Program Function: NOISEVOLT

EXPORT NOISEVOLT(b,r)
BEGIN
// Noise Voltage in V
// Input: B=bandwidth (Hz)
// Input: R=resistor (Ω)
// input numbers only
√(1.6ᴇ−20*b*r);
END;

HP 42S Program for Solver:  NSEVT

00 { 37-Byte Prgm }
01▸LBL "NSEVT"
02 MVAR "B"
03 MVAR "R"
04 MVAR "En"
05 16ᴇ-21
06 RCL× "B"
07 RCL× "R"
08 SQRT
09 RCL- "En"
10 .END.

Example (FIX 4):

Input:  B = 31,000 Hz, R = 950 Ω
Result:  e_n = 6.8644e-7 V

Sources: 

Ball, John A.  Algorithms For RPN Calculators  John Wiley & Sons: New York  1978.  ISBN 0-471-03070-8

Eddie

All original content copyright, © 2011-2018.  Edward Shore.   Unauthorized use and/or unauthorized distribution for commercial purposes without express and written permission from the author is strictly prohibited.  This blog entry may be distributed for noncommercial purposes, provided that full credit is given to the author.  Please contact the author if you have questions.