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| Keywords: Transmission line animation open short2.gif en Two transmission lines the top one terminated at an open-circuit the bottom terminated at a short circuit Black dots represent electrons and the arrows show the electric field 2014-11-11 own Sbyrnes321 other versions cc-zero Source code <source lang python> C Steven Byrnes 2014-2016 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 Use Python 3 style division a/b is real division a//b is integer division from __future__ import division import subprocess os directory_now os path dirname os path realpath __file__ import pygame as pg from numpy import pi linspace cos sin frames_in_anim 50 animation_loop_seconds 2 5 time in seconds for animation to loop one cycle bgcolor 255 255 255 background is white ecolor 0 0 0 electrons are black wire_color 200 200 200 wire color is light gray split_line_color 0 0 0 line down the middle is black arrow_color 140 0 0 arrows are red pygame draws pixel-art not smoothed Therefore I am drawing it bigger then smoothly shrinking it down img_height 330 img_width 900 final_height 110 final_width 300 ~23 megapixel limit for wikipedia animated gifs assert final_height final_width frames_in_anim < 22e6 transmission line wire length and thickness and y-coordinate of the top of each wire tl_length int img_width 9 tl_thickness 27 tl_open_top_y 30 tl_open_bot_y tl_open_top_y + 69 tl_short_top_y 204 tl_short_bot_y tl_short_top_y + 69 tl_open_center_y int tl_open_top_y + tl_open_bot_y + tl_thickness / 2 tl_short_center_y int tl_short_top_y + tl_short_bot_y + tl_thickness / 2 wavelength 1 1 tl_length e_radius 4 dimensions of triangular arrow head this is for the longest arrows; it's scaled down when the arrow is too small arrowhead_base 9 arrowhead_height 15 width of the arrow line arrow_width 6 number of electrons spread out over the transmission line top plus bottom num_electrons 100 max_e_displacement is defined here as a multiple of the total electron path length roughly twice the width of the image because we're adding top + bottom max_e_displacement 1/40 num_arrows 20 max_arrow_halflength 18 def tup_round tup round each element of a tuple to nearest integer return tuple int round x for x in tup def draw_arrow surf x tail_y head_y draw a vertical arrow Coordinates do not need to be integers calculate dimensions of the triangle; it's scaled down for short arrows if abs head_y - tail_y > 1 5 arrowhead_height h arrowhead_height b arrowhead_base else h abs head_y - tail_y / 1 5 b arrowhead_base h / arrowhead_height if tail_y < head_y downward arrow triangle tup_round x head_y tup_round x - b head_y - h tup_round x + b head_y - h triangle_middle_y head_y - h/2 else upward arrow triangle tup_round x head_y tup_round x - b head_y + h tup_round x + b head_y + h triangle_middle_y head_y + h/2 pg draw line surf arrow_color tup_round x tail_y tup_round x triangle_middle_y arrow_width pg draw polygon surf arrow_color triangle 0 def e_path_open param time param is an abstract coordinate that goes from 0 to 1 as the electron position goes right across the top wire then left across the bottom wire time goes from 0 to 2pi over the course of the animation This returns a dictionary 'pos' is x y the coordinates of the corresponding point on the electron dot path; 'displacement' is the displacement of an electron at this point relative to its equilibrium position between -1 and -1 ; and 'charge' is the net charge at this point between -1 and +1 This is for the open-circuit line d is a vertical offset between the electrons and the wires d e_radius + 2 pad is how far to extend the transmission line beyond the image borders since those electrons may enter the image a bit pad 36 path_length 2 tl_length + pad howfar param path_length go right along top transmission line if howfar < tl_length + pad x howfar - pad y tl_open_top_y + tl_thickness - d displacement -sin 2 pi tl_length - x / wavelength cos time charge cos 2 pi tl_length - x / wavelength cos time return 'pos' x y 'displacement' displacement 'charge' charge go left along bottom transmission line x path_length - howfar - pad y tl_open_bot_y + d displacement -sin 2 pi tl_length - x / wavelength cos time charge -cos 2 pi tl_length - x / wavelength cos time return 'pos' x y 'displacement' displacement 'charge' charge def e_path_short param time Same as e_path_open above but for the short-circuit line d is a vertical offset between the electrons and the wires d e_radius + 2 pad is how far to extend the transmission line beyond the image borders since those electrons may enter the image a bit pad 36 path_length 2 tl_length + pad + 4 d + tl_short_bot_y - tl_short_top_y - tl_thickness howfar param path_length at the beginning go right along top wire if howfar < tl_length + pad x howfar - pad y tl_short_top_y + tl_thickness - d displacement cos 2 pi tl_length - x / wavelength cos time charge sin 2 pi tl_length - x / wavelength cos time return 'pos' x y 'displacement' displacement 'charge' charge at the end go left along bottom wire if path_length - howfar < tl_length + pad x path_length - howfar - pad y tl_short_bot_y + d displacement cos 2 pi tl_length - x / wavelength cos time charge -sin 2 pi tl_length - x / wavelength cos time return 'pos' x y 'displacement' displacement 'charge' charge in the middle charge 0 displacement cos time top part of short if tl_length + pad < howfar < tl_length + pad + d x howfar - pad y tl_short_top_y + tl_thickness - d bottom part of short elif tl_length + pad < path_length - howfar < tl_length + pad + d x path_length - howfar - pad y tl_short_bot_y + d vertical part of short else x tl_length + d y tl_short_top_y + tl_thickness - d + howfar-pad - tl_length + d return 'pos' x y 'displacement' displacement 'charge' charge def e_path param time which return e_path_open param time if which 'open' else e_path_short param time 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 time 2 pi frame / frames_in_anim initialize surface surf pg Surface img_width img_height surf fill bgcolor ; draw transmission line pg draw rect surf wire_color 0 tl_open_top_y tl_length tl_thickness pg draw rect surf wire_color 0 tl_open_bot_y tl_length tl_thickness pg draw rect surf wire_color 0 tl_short_top_y tl_length tl_thickness pg draw rect surf wire_color 0 tl_short_bot_y tl_length tl_thickness pg draw rect surf wire_color tl_length tl_short_top_y tl_thickness tl_short_bot_y - tl_short_top_y + tl_thickness draw line down the middle pg draw line surf split_line_color 0 img_height//2 img_width img_height//2 12 draw electrons Remember param is an abstract coordinate that goes from 0 to 1 as the electron position goes right across the top wire then left across the bottom wire equilibrium_params linspace 0 1 num num_electrons for which in 'open' 'short' for eq_param in equilibrium_params temp e_path eq_param time which param_now eq_param + max_e_displacement temp'displacement' xy_now e_path param_now time which 'pos' pg draw circle surf ecolor tup_round xy_now e_radius draw arrows arrow_params linspace 0 0 49 num num_arrows for which in 'open' 'short' center_y tl_open_center_y if which 'open' else tl_short_center_y for i in range len arrow_params a arrow_paramsi arrow_x e_path a time which 'pos'0 charge e_path a time which 'charge' head_y center_y + max_arrow_halflength charge tail_y center_y - max_arrow_halflength charge draw_arrow surf arrow_x tail_y head_y shrink the surface to its final size and save it shrunk_surface pg transform smoothscale surf final_width final_height pg image save shrunk_surface filename_listframe seconds_per_frame animation_loop_seconds / frames_in_anim frame_delay str int seconds_per_frame 100 Use the convert command part of ImageMagick to build the animation command_list 'convert' '-delay' frame_delay '-loop' '0' + filename_list + 'anim gif' 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 </source> Transmission lines Animations of electronics Impedance Animations of vibrations and waves Images with Python source code Animated GIF files | ||||
