TimeRuler

TimeRuler is a time-space measuring tool, using light-painting technique. It can be used for fun, for measuring high speed movement in different sports or as an educational device for schools.

What you need:

• Arduino UNO, or similar
• 13 pcs. 3V ultra bright dome LED
• jump wire
• mini breadboard
• 9V battery
• plywood
• wood adhesive
• glue gun
• tracing paper, black cardboard, carbon paper
• silver paint or mirror sheets
• fretsaw
• Camera with long exposure function

1. insert 11 LEDs into the breadboard
2. connect the LEDs anode/longer pins (+) with pin 3-13
3. connect the cathode/shorter (-) pins to GND.
4. open Arduino and open the attached code file. If you don't have the software, than download it here.
5. disconnect the battery, connect the Arduino with your computer via USB cable provided.
6. take a look at the code to see what it does. When you are testing you can set longer times so you can check if the LEDs are lit up correctly at a perceivable speed.
   

   int delt=9; //delay time 9 ms - set this to 99
   int blit=0.1; //delay time 0.1 ms - set this to 1

7. upload the code to Arduino and see the result

Build a box from plywood. The assembled box size is 62*85*77 mm (2.44*3.34*3.03 inch)

1. print the attached PDF file
2. copy with the help of a carbon paper the red outline on the plywood lid.

3. copy with the help of a carbon paper the blue outline on the black cardboard and cut out the shapes carefully. Stick tracing paper on the back of the cardboard - this will diffuse the light. These blue lines are inset 1 mm, because it is hard to make precise holes in the plywood.

4. Cut 15 mm (0.59 inch) wide plywood strips than glue strips around the holes. You can paint reflective silver later or stick mirror sheets - this process helps bounce more light out through the holes.

1. Solder the wires to the LEDs, than insulate
2. Test LEDs by mounting all of them in the right hole. If right, than fix them with hot glue.
3. glue some black hobby foam strips on the back of the lid, so when you close no light could escape on the edges.
4. mount a colored piece of plastic sheet inside the longest slit.

Make a hole, where the Arduino has it's power socket, insert the plug, than mount the battery outside the box with a velcro. I used this this improvised ON-OFF system instead of buttons. to have smoother and faster start. When i push the cable to the plus end, than the animation starts automatically.

Set your camera to a few seconds long exposure with self timer, than paint some light in a dark space. Adjust ISO and aperture until you got the desired quality. Additionally if you want the painter to be visible in the picture you can give him/her a radio trigger, which is triggering a flashlight.

Play, Measure, Enjoy

Thanks for Midlands Makerspace Athlone for the helping me with Arduino.