DescriptionDelta PWM.png	English: Principle of the delta Pulse Width Modulation (PWM).
Date	25 June 2006
Source	Own work, using gnuplot, python and scipy   This plot was created with Gnuplot by n.
Author	Cyril BUTTAY
Permission (Reusing this file)	as licensed
Other versions	English .png English .svg Russian .svg

File:Delta PWM.svg is a vector version of this file. It should be used in place of this PNG file when not inferior. File:Delta PWM.png → File:Delta PWM.svg For more information, see Help:SVG. In other languages Alemannisch ∙ العربية ∙ беларуская (тарашкевіца) ∙ български ∙ বাংলা ∙ català ∙ нохчийн ∙ čeština ∙ dansk ∙ Deutsch ∙ Ελληνικά ∙ English ∙ British English ∙ Esperanto ∙ español ∙ eesti ∙ euskara ∙ فارسی ∙ suomi ∙ français ∙ Frysk ∙ galego ∙ Alemannisch ∙ עברית ∙ hrvatski ∙ magyar ∙ հայերեն ∙ Bahasa Indonesia ∙ Ido ∙ italiano ∙ 日本語 ∙ ქართული ∙ 한국어 ∙ lietuvių ∙ македонски ∙ മലയാളം ∙ Bahasa Melayu ∙ norsk bokmål ∙ Plattdüütsch ∙ Nederlands ∙ norsk nynorsk ∙ norsk ∙ occitan ∙ polski ∙ prūsiskan ∙ português ∙ português do Brasil ∙ română ∙ русский ∙ sicilianu ∙ Scots ∙ slovenčina ∙ slovenščina ∙ српски / srpski ∙ svenska ∙ தமிழ் ∙ ไทย ∙ Türkçe ∙ татарча / tatarça ∙ українська ∙ vèneto ∙ Tiếng Việt ∙ 中文 ∙ 中文（中国大陆） ∙ 中文（简体） ∙ 中文（繁體） ∙ 中文（马来西亚） ∙ 中文（新加坡） ∙ 中文（臺灣） ∙ 中文（臺灣） ∙ +/−

 

I, the copyright holder of this work, hereby publish it under the following licenses:

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License.http://www.gnu.org/copyleft/fdl.htmlGFDLGNU Free Documentation Licensetruetrue

	This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
	You are free: to share – to copy, distribute and transmit the work to remix – to adapt the work Under the following conditions: attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.
	This licensing tag was added to this file as part of the GFDL licensing update.http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue

This file is licensed under the Creative Commons Attribution-Share Alike 2.5 Generic, 2.0 Generic and 1.0 Generic license.

You are free:

• to share – to copy, distribute and transmit the work
• to remix – to adapt the work

Under the following conditions:

• attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
• share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.

https://creativecommons.org/licenses/by-sa/2.5CC BY-SA 2.5 Creative Commons Attribution-Share Alike 2.5 truetrue

You may select the license of your choice.

This file was generated using the following python code (requires the module scipy)

#!/usr/bin/python
# this file generates data and the gnuplot file used for the delta pwm plot 
# needs python, scipy and gnuplot (4.0 used)
from scipy import *

freq= 0.05 	# frequency of the reference signal
step=1e-2  	# calculation time step
hysteresis=0.15	# hysteresis of the delta pwm
current_increase=0.5 # rate of increase (or decrease) in the output current
current_decrease=-0.5

direction=0	# direction=0 when output current increase, 1 otherwise
current=[0]	# this is the current waveform
pwm=[0]		# This vector is the pwm signal
grid=["0"]	# this vector contains the x-values at which the pwm signal
		# changes state
file = open("data.dat","w") # the data file

for i in range(int(1/(freq*step))):
    reference=sin(i*step*freq*2*pi)
    high_limit=reference+hysteresis
    low_limit=reference-hysteresis
    if direction==0:
        if current[i]<high_limit: 	#if current is increasing, but we still
				 	#are under the upper limit, carry on
            current.append(current[i]+current_increase*step)
            pwm.append(1)		
        else:				#else change pwm state
            current.append(current[i]+current_decrease*step)
            direction=1
	    grid.append("%s"%(i*step)) 	#stores the time value at which the 
					#pwm changed state  
            pwm.append(0)            
    elif direction==1:			#if current is decreasing, but we still
				 	#are over the lower limit, carry on
        if current[i]>low_limit:
            current.append(current[i]+current_decrease*step)
            pwm.append(0)           
        else:				#else change pwm state
            current.append(current[i]+current_increase*step)
            direction=0
	    grid.append("%s"%(i*step)) 	#stores the time value at which the 
					#pwm changed state
            pwm.append(1)
    file.write('%s\t%s\t%s\t%s\t%s\t%s\n'%(i*step,pwm[i],current[i],
                                          high_limit,
                                          low_limit,
                                          reference))
file.close()				# end of data generation

xtics=',"" '.join(grid)			# creates a string used for the x-tics
file = open("delta.plt","w")		# generates the gnuplot file
file.write("""
# This file is used to generate a plot that explains the 
# principle of the delta pwm

# graph configuration
set terminal postscript eps enhanced "Times-Roman" 24 color solid
set encoding iso_8859_15
unset title
set line style 1 lt 3 lw 3 pt 0 ps 0
set line style 2 lt 2 lw 1 pt 0 ps 0
set line style 3 lt 8 lw 2 pt 0 ps 0
set line style 4 lt 4 lw 3 pt 0 ps 0
set border 15 lt 7 lw 4

set grid xtics ytics
set xlabel ""
set format x ""
set bmargin 0
set tmargin 0
  
set ytics ("0" 0)
set xtics (%s)  

set output "delta.eps"
set multiplot
	set ylabel "Analog signals"
	set origin 0,0.54
	set size 1,0.45
	plot [0:19][-1.2:1.2] "data.dat" using 1:6 ls 3 title 'Reference' w l,\
	'' using 1:4 w l ls 2 title 'Limits',\
	'' using 1:5 w l ls 2 title '',\
	'' using 1:3 w l ls 1 title 'Output'

	set ytics ("0" 0, "1" 1)
	set ylabel "PWM signal"
	set xlabel "Time"
	set origin 0,0.09
	plot [0:19][-0.25:1.25] 'data.dat' using 1:2 ls 4 title '' w l
unset multiplot	""" %xtics)
file.close() 				# end of the gnuplot file.

This generates two files, 'data.dat' (data) and 'sigma.plt' (gnuplot source). gnuplot sigma.plt then generates a eps file, which is converted in png using imagemagick.