video takes a lot of space. since time-lapse videos are much more interesting if you cover a big time interval you either have to have a huge memory card or you manage to turn down the amount of data that comes in. i decided to do the latter. since canon cams don’t come with a time-lapse function built in, one has to find an external time that does the job. there are several cheap external cable timers available. they just have one problem. they just do time intervals from 1 to about 9999 seconds. i needed less. 300 ms (0,3 sec) should be my smallest interval. so i built my own.

the second try - opened box

the second iteration is built on an arduino diecimila. on top i use a prototyping board which holds a 16×2 display. as input there is a potentiometer that chooses the timing interval. the display shows exactly what interval is chosen.

final 2nd iteration

to reduce the risk of toasting my camera i separated the arduino circuit with an opto-isolator to the cable.

the next step is to reduce the size of the box by finding a smaller form factor and using the arduino pro mini.

here is the arduino code:

/*
  Time-lapse timer

Copyright 2011 Florian Klien. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are
permitted provided that the following conditions are met:

   1. Redistributions of source code must retain the above copyright notice, this list of
      conditions and the following disclaimer.

   2. Redistributions in binary form must reproduce the above copyright notice, this list
      of conditions and the following disclaimer in the documentation and/or other materials
      provided with the distribution.

THIS SOFTWARE IS PROVIDED BY Florian Klien ``AS IS AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL Florian Klien OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include <LiquidCrystal.h>

#define LCDRS 11
#define LCDENABLE 10
#define LCDD4 7
#define LCDD5 6
#define LCDD6 5
#define LCDD7 4
#define POTPIN 2 // potentiometer pin
#define LEDPIN 12 // pin for an optional led
#define SWITCHPIN 8
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(LCDRS, LCDENABLE, LCDD4, LCDD5, LCDD6, LCDD7);

double val = 0;
int ts = 0;
unsigned long int steps[] = {333,500,750,
               1000,1500,2000,
               2500,3000,4000,
               5000,6000,7000,
               8000,9000,10000,
               12000,15000,20000,
               25000,30000,35000,
               40000,45000,50000,
               55000,60000,90000,
               120000,240000,300000,
               360000,420000,480000,
               540000,600000,900000,
               1200000
             }; // in ms

unsigned long lasttime = 0;

void setup() {
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  // Print a message to the LCD.
  lcd.print("timer set to:");
  Serial.begin(9600);
  //lasttime = millis();
  pinMode(LEDPIN, OUTPUT);
  pinMode(SWITCHPIN, OUTPUT);
  digitalWrite(LEDPIN,HIGH);
  delay(500);
  digitalWrite(LEDPIN,LOW);
}

void loop() {
  val = analogRead(POTPIN);
  ts = map(val, 0, 1023, 0, 37);
  lcd.setCursor(0, 1);
  double time = (float)steps[ts]/1000;
  lcd.print(time);
  lcd.print(" sec ");
  lcd.print((float)(millis()-lasttime)/1000);
  lcd.print("    ");
  if((millis()-lasttime) > steps[ts]){
    digitalWrite(LEDPIN, HIGH);
    digitalWrite(SWITCHPIN,HIGH);
    delay(100);
    digitalWrite(LEDPIN, LOW);
    digitalWrite(SWITCHPIN,LOW);
    lasttime = millis();
  }
}

update:
here is a little testvideo:

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the camera i used is my canon ixus 750. since the lense on this camera is rather low i had to improve the camera stand. i added some aluminum ducts to make it higher and to make the camera see the street. about 7 centimeters were enough.

since i was not able to get the CHDK timelapse to work i shot video. to generate a timelapse i used ffmpeg to extract images out of the video and to unite them to a timelapse video.
using this tutorial and the man pages i was able to come up with this:

#!/bin/bash
# sample usage: ./timelapsify.sh input.avi output.mp4
mkdir ffmpeg_temp
ffmpeg -i $1 -r 1.4 -f image2 ffmpeg_temp/%05d.png
ffmpeg -i ffmpeg_temp/%05d.png -sameq $2
rm -rf ./ffmpeg_temp

note that it is important for ffmpeg to have the images you use to generate the timelapse video in order and sequenced. if you decide to delete some images you have to rename them and must not leave gaps.
also you may have to vary the rate (i used: 1.4) acording to the speed of your input video and the speed of the output video you want to have.

one step i did between extracting and generating the timelapse was sending it through imagemagick to blend the speedometer. using info from this mailing list:

#!/bin/bash
#usage: pixelate_circle.sh IN.file OUT.file center_x_coord center_y_coord border_x_coord border_y_coord
convert $1 \( -clone 0 -scale 10% -scale 1000% \) \
\( -clone 0 -gamma 0 -fill white \
-draw "circle ${3},${4},${5},${6}"\
\) -composite $2

of course this has to be done for every image

and here is the resulting video:

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