resistorswitchzeug.py

#!/usr/bin/python

from e_series import e_series

#http://www.mikrocontroller.net/topic/331314

#Thevenin-Aequiv. zu Spannungsteiler aus R1=R6=10k mit R3=R4=0

Vx=2.5

Rx=5000.0

#list with the differences of consecutive list elements

def listdiff(t):

    return [j-i for i, j in zip(t[:-1], t[1:])]

#value of two parallel resistors

def par(a, b):

    return (a * b) / (a + b)

#factor of voltage divider

def vdiv(top, bottom):

    return bottom / (top + bottom)

# Lin. ueberlagerung der Spannungen von Schaltern und Spgsteiler

# fuer einen Schalterzustand

# ra = R2, rb = R5

def voltage(sa, sb, ra, rb):

    if sa == None and sb == None:

        return Vx

    if sa == None:

        return Vx * vdiv(Rx, rb) + sb * vdiv(rb, Rx)

    if sb == None:

        return Vx * vdiv(Rx, ra) + sa * vdiv(ra, Rx)

    return Vx * vdiv(Rx, par(ra, rb)) + sa * vdiv(ra, par(rb, Rx)) + sb * vdiv(rb, par(Rx, ra))

# alle moeglichen Schaltzustaende. None heisst offen

def switch_states():

    for a in [0.0, None, 5.0]:

        for b in [0.0, None, 5.0]:

            yield a, b

# list mit allen Spannungswerten am ADC, die bei den Widerstaenden ra und rb moeglich sind

def all_voltages(ra, rb):

    t = list()

    for sa, sb in switch_states():

        t.append(voltage(sa, sb, ra, rb))

    return t

# kleinste Spannungsdifferenz

def smallest_voltagediff(ra, rb):

    vs = all_voltages(ra, rb)

    vs.sort()

    diffs = listdiff(vs)

    return min(diffs)

if __name__ == '__main__':

    a = list()

    # 100R bis 220k sollten reichen:

    for ra in e_series(96, 100.0, 220000.0, adj = True):

        for rb in e_series(96, ra, 220000.0, adj = True):

            a.append([ra, rb, smallest_voltagediff(ra, rb)])

    # die groesste kleinste spannungsdifferenz suchen:

    best_res = max(a, key=lambda el: el[2])

    print best_res