resistor.py

Created by vnap0v

Created on May 22, 2025

1.81 KB

This script finds the best approximation of an arbitrary resistance value using two series or two parallel resistors out of the standard E12 and E24 series. It imports no modules.Tested on the calculator using software version 23.2.6.

E12 = (1.0,1.2,1.5,1.8,2.2,2.7,3.3,3.9,4.7,5.6,6.8,8.2)
E24 = (1.0,1.1,1.2,1.3,1.5,1.6,1.8,2.0,2.2,2.4,2.7,3.0, \
       3.3,3.6,3.9,4.3,4.7,5.1,5.6,6.2,6.8,7.5,8.2,9.1)  

def series_parallel(Rx, Evalues):
    Rser_best=0;Rpar_best=0
    for exponent1 in range(1,6):
        for manitissa1 in Evalues:
            R1=float(str(manitissa1)+"E"+str(exponent1))
            if R1==Rx: # the requested res value exists in the Evalues
                return (round(R1),)
            for exponent2 in range(1,6):
                for manitissa2 in Evalues:
                    R2=float(str(manitissa2)+"E"+str(exponent2))
                    Rs=R1+R2
                    Rp=1/(1/R1+1/R2)
                    if abs(Rs-Rx)<abs(Rser_best-Rx):
                        Rser_best=Rs
                        R1ser_best=round(R1)
                        R2ser_best=round(R2)
                    if abs(Rp-Rx)<abs(Rpar_best-Rx):
                        Rpar_best=Rp
                        R1par_best=round(R1)
                        R2par_best=round(R2)
    return (R1ser_best,R2ser_best,R1par_best,R2par_best)

def find_best_res(rx=None):
    print("Match Rx with 2 res.")
    if rx==None:
        rx=float(input("Resistance value? "))
    else:
        print("Resistance value =",rx)
    E12match=series_parallel(rx,E12)
    E24match=series_parallel(rx,E24)
    if len(E12match)==1:
        print("Value exists as E12\n",E12match[0])
    else:
        print("E12 values:")
        print("Best series combination\n",*E12match[0:2])
        print("Best parallel combination\n",*E12match[2:4])
    if len(E24match)==1:
        print("Value exists as E24\n", E24match[0])
    else:
        print("E24values:")
        print("Best series combination\n",*E24match[0:2])
        print("Best parallel combination\n",*E24match[2:4])
        
find_best_res()