File:Transmission line animation.gif
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Transmission_line_animation.gif (300 × 100 pixels, file size: 112 KB, MIME type: image/gif, looped, 30 frames, 1.8 s)
File information
Structured data
Captions
Captions
A lossless transmission line, terminated at an impedance-matched load resistor (box on right). Red color indicates high voltage, and blue indicates low voltage. Black dots represent electrons.
Summary
[edit]DescriptionTransmission line animation.gif |
English: A lossless transmission line, terminated at an impedance-matched load resistor (box on right). Red color indicates high voltage, and blue indicates low voltage. Black dots represent electrons. (See also File:Transmission_line_animation3.gif for a newer and simpler version.) |
Date | |
Source | Own work |
Author | Sbyrnes321 |
Licensing
[edit]I, the copyright holder of this work, hereby publish it under the following license:
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This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication. |
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.
http://creativecommons.org/publicdomain/zero/1.0/deed.enCC0Creative Commons Zero, Public Domain Dedicationfalsefalse |
Source code
[edit]"""
(C) Steven Byrnes, 2013. This code is released under the MIT license
http://opensource.org/licenses/MIT
This code runs in Python 2.7 or 3.3. It requires imagemagick to be installed;
that's how it assembles images into animated GIFs.
"""
from __future__ import division
import pygame as pg
from numpy import cos, pi, sin, asarray
import subprocess, os
directory_now = os.path.dirname(os.path.realpath(__file__))
frames_in_anim = 30
animation_loop_seconds = 2 #time in seconds for animation to loop one cycle
bgcolor = (255,255,255) #white
linecolor = (0,0,0) #outline of resistor is black
ecolor = (0,0,0) #electron color is black
img_height = 100
img_width = 300
#transmission line wire length and thickness, and y-coordinate of each wire
tl_length = img_width * 6//7
tl_thickness = 5
tl_top_y = img_height*4//9
tl_bot_y = img_height*5//9 - tl_thickness//2 #second term is to keep it symmetric
wavelength = 0.6 * tl_length
resistor_length = img_height//2
resistor_width = resistor_length//3
resistor_center = (img_width - resistor_width*3//2, img_height//2)
top_lead_path = [(tl_length, tl_top_y + tl_thickness-1),
(tl_length, img_height//9),
(resistor_center[0], img_height//9),
resistor_center]
bot_lead_path = [(x,img_height-y+1) for (x,y) in top_lead_path]
lead_thickness = 2
def rgb_from_V(V):
"""
voltage V varies -1 to +1. Return a color as a function of V.
Color is a 3-tuple red,green,blue, each 0 to 255.
"""
return (100+100*V, 100 - 100*V, 100-100*V)
def tup_round(tup):
"""
round each element of a tuple to nearest integer
"""
return tuple(int(round(x)) for x in tup)
def make_wire_surf(phase_at_left):
"""
make a pygame surface representing a colored wire. startphase is phase
at left side of the wire.
"""
imgarray = [[rgb_from_V(cos(phase_at_left + 2*pi*x/wavelength))
for y in range(tl_thickness)] for x in range(tl_length)]
return pg.surfarray.make_surface(asarray(imgarray))
def make_resistor_surf(phase_at_top):
"""
make a pygame surface representing the resistor. topphase is phase at top
"""
imgarray = [[rgb_from_V(cos(phase_at_top) * (1 - 2*y/resistor_length))
for y in range(resistor_length)]
for x in range(resistor_width)]
surf = pg.surfarray.make_surface(asarray(imgarray))
pg.draw.rect(surf,linecolor,surf.get_rect(),1) #1-pixel black outline
return surf
def e_path(param, phase_top_left):
"""
as param goes 0 to 1, this returns {'pos': (x, y), 'phase':phi},
where (x,y) is the coordinates of the corresponding point on the electron
dot path, and phi is the phase for an electron at that point on the path.
phase_top_left is phase of the left side of the top wire.
"""
d = 3 #pixels between electron path and corresponding wires
path_length = ( 2*(tl_length - d) #transmission lines
+ 2*(img_height//3) #left vertical leads
+ 2*(resistor_center[0] - tl_length + 2*d + lead_thickness)
+ 2*(resistor_length//2 - img_height//9) #right vertical leads
+ resistor_length) #through resistor
howfar = param * path_length
#move right across top transmission line
if howfar < tl_length - d:
x = howfar
y = tl_top_y - d
phase = phase_top_left + 2 * pi * x / wavelength
return {'pos':(x,y), 'phase':phase}
howfar -= (tl_length - d)
#move up lead
if howfar < img_height//3:
x = tl_length - d
y = tl_top_y - d - howfar
phase = phase_top_left + 2 * pi * tl_length / wavelength
return {'pos':(x,y), 'phase':phase}
howfar -= img_height//3
#move right to above resistor
if howfar < (resistor_center[0]- tl_length) + 2*d + lead_thickness:
x = tl_length - d + howfar
y = img_height//9 - d
phase = phase_top_left + 2 * pi * tl_length / wavelength
return {'pos':(x,y), 'phase':phase}
howfar -= (resistor_center[0] - tl_length) + 2*d + lead_thickness
#move down to top of resistor
if howfar < (resistor_length//2 - img_height//9):
x = resistor_center[0] + d + lead_thickness
y = img_height//9 - d + howfar
phase = phase_top_left + 2 * pi * tl_length / wavelength
return {'pos':(x,y), 'phase':phase}
howfar -= (resistor_length//2 - img_height//9)
#move down resistor
if howfar < resistor_length:
x = resistor_center[0] + resistor_width//2 + d
y = resistor_center[1] - resistor_length//2 + howfar
phase = phase_top_left + 2 * pi * tl_length / wavelength
return {'pos':(x,y), 'phase':phase}
howfar -= resistor_length
#beyond here use the mirror symmetry
flipdata = e_path(1-param, phase_top_left)
flipdata['pos'] = (flipdata['pos'][0], img_height - flipdata['pos'][1] + 2)
return flipdata
def main():
#Make and save a drawing for each frame
filename_list = [os.path.join(directory_now, 'temp' + str(n) + '.png')
for n in range(frames_in_anim)]
for frame in range(frames_in_anim):
phase_top_left = -2 * pi * frame / frames_in_anim
phase_top_right = phase_top_left + 2 * pi * tl_length / wavelength
#initialize surface
surf = pg.Surface((img_width,img_height))
surf.fill(bgcolor);
#draw transmission line
top_wire_surf = make_wire_surf(phase_top_left)
bottom_wire_surf = make_wire_surf(phase_top_left + pi)
surf.blit(top_wire_surf, (0, tl_top_y))
surf.blit(bottom_wire_surf, (0, tl_bot_y))
#draw lead wires
color = rgb_from_V(cos(phase_top_right))
pg.draw.lines(surf,color,False,top_lead_path,lead_thickness)
color = rgb_from_V(cos(phase_top_right + pi))
pg.draw.lines(surf,color,False,bot_lead_path,lead_thickness)
#draw resistor
resistor_surf = make_resistor_surf(phase_top_right)
surf.blit(resistor_surf, (resistor_center[0] - resistor_width//2,
resistor_center[1] - resistor_length//2))
#draw electrons
num_electrons = 100
equilibrium_params = [x/(num_electrons-1) for x in range(num_electrons)]
phases = [e_path(a, phase_top_left)['phase'] for a in equilibrium_params]
now_params = [equilibrium_params[i] + sin(phases[i])/(1.3*num_electrons)
for i in range(num_electrons)]
coords = [e_path(a, phase_top_left)['pos'] for a in now_params]
for coord in coords:
pg.draw.circle(surf, ecolor, tup_round(coord), 2, 0)
pg.image.save(surf, filename_list[frame])
seconds_per_frame = animation_loop_seconds / frames_in_anim
frame_delay = str(int(seconds_per_frame * 100))
command_list = ['convert', '-delay', frame_delay, '-loop', '0'] + filename_list + ['anim.gif']
# Use the "convert" command (part of ImageMagick) to build the animation
subprocess.call(command_list, cwd=directory_now)
# Earlier, we saved an image file for each frame of the animation. Now
# that the animation is assembled, we can (optionally) delete those files
if True:
for filename in filename_list:
os.remove(filename)
main()
File history
Click on a date/time to view the file as it appeared at that time.
Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 14:50, 24 February 2014 | ![]() | 300 × 100 (112 KB) | Sbyrnes321 (talk | contribs) | smaller file size, by switching from images2gif.py to imagemagick |
13:40, 30 July 2012 | ![]() | 300 × 100 (258 KB) | Sbyrnes321 (talk | contribs) |
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