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"""
# Xytronic LF-1600
# Open Source firmware
# R/C network calculation
#
# Copyright (c) 2019 Michael Buesch <m@bues.ch>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""
import math
__all__ = [
"RCNet",
]
class RCNet(object):
"""Discrete R/C network calculation.
"""
__slots__ = (
"r", # Resistor value, in Ohms.
"c", # Capacitor value, in Farad.
"v", # Capacitor voltage.
"i", # Network current, in Ampere.
)
def __init__(self, r, c, v=None, q=None):
self.r = r
self.c = c
self.v = v or 0.0
if q is not None:
assert(v is None)
self.q = q
self.i = 0.0
@property
def q(self):
"""Get charge, in Coulomb.
"""
return self.c * self.v
@q.setter
def q(self, newQ):
"""Set charge, in Coulomb.
"""
self.v = newQ / self.c
def calc(self, vIn, dt):
"""Calculate the next discrete step.
Returns the new C voltage.
"""
c, r = self.c, self.r
dv = vIn - self.v
fact = math.exp((-1.0 / (r * c)) * dt)
self.i = (dv / r) * fact
self.v += dv * (1.0 - fact)
return self.v
def __str__(self):
return "v=%.3f V, i=%.3f mA, q=%.3f uC" % (
self.v,
self.i * 1e3,
self.q * 1e6)
if __name__ == "__main__":
import matplotlib.pyplot as plt
rc = RCNet(r=(10e3),
c=(220e-6),
q=0.0)
dt = 0.01
times = [t * dt for t in range(500)]
values = []
for t in times:
rc.calc(vIn=(5.0 if t <= 3.0 else -2.0),
dt=dt)
print("t=%.3f s, %s" % (t, str(rc)))
values.append((rc.q * 1e6, rc.i * 1e3, rc.v))
fig, ax = plt.subplots(3, sharex=True)
ax[0].plot(times, [val[0] for val in values], label="Q (uC)")
ax[0].legend()
ax[1].plot(times, [val[1] for val in values], label="I (mA)")
ax[1].legend()
ax[2].plot(times, [val[2] for val in values], label="U (V)")
ax[2].legend()
ax[2].set_xlabel("t (s)")
plt.show()
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