Fun with Computers – Arduino POV Project

Fun with Computers – Arduino POV Project

Sep 2, 2011

If you are looking for some fun with your Computer and have an amateur interest in Electronics then the Arduino is the ultimate companion. The Arduino is cheap, easy to use, easy to program and the possibilities are endless.

This is my first Arduino POV project. POV – Persistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina.

http://en.wikipedia.org/wiki/Persistence_of_vision

Put simply; it’s a programmable sign. You can have it display any message or picture you set. We are basically flashing the 5 LED lights in sequence while a motor turns the lights around. Because the arm is moving at speed you are seeing the lights 20 times per a second in differing sequences tricking the eye into seeing it as a banner.

Displaying the Message "MICROED"

Aim of the Project

Put simply, its a programmable sign. You can have it display any message or picture you set. We are basically flashing the 5 LED lights in sequence while a motor turns the lights around. Because the arm is moving at speed you are seeing the lights 20 times per a second in differing sequences tricking the eye into seeing it as a banner.

Parts List

1 x Arduino Compatible Processor (I used a KitTen from freetronics only $26.95 AUD http://www.freetronics.com/products/kitten)
5 x SMD LEDs or 5 x LED
5 x 1K Resistor
1 x 8 pin 90-degree locking header

Battery, LEDs and Arduino Mounted on the propeller ready for testing

1 x 40 pin terminal strip
1 x 9v Battery Clip
1 x 2.1mm dc power line female connector
Connecting Wire (I used an old IDE Cable)
2 x Small PCB Board
1 x Ruler or suitable board for arm
1 x Small DC Motor (used Tape Player motor)
1 x 9v Battery
1 x dead 9v Battery for counterweight
Suitable Base (old CDROM)

Tools

Soldering Iron
Hot Glue Gun (my best friend)

Technical Background Required

Some basic understanding of electronics and Programming can be handy but not necessary.

Assembly

Take an old IDE cable and split off 6 wires.

Mount your LED’s on one of the small PCB boards. If you use SMD tape then you can simply cut the strip up and stick them on the board.

Solder a piece of cable across the negative side of all the LED’s and then the other connecting leads for the positive sides of the LEDs.

Solder the other end of the cable to the 90 degree locking header.

Now take the other PCB board and solder the 90 degree header on one end of the PCB and the terminal strip to the other end of the PCB board.

Solder the Terminal Strip to the other side and other end of the board.
Solder the individual resistors.

Solder your 9V battery clip to the DC power line connector.

The Base and Arm

Hot Glue a suitable DC motor to the CDROM unit (or any suitable heavy base).

Hot glue your battery, Arduino board and LED’s to your ruler/arm.

Hot Glue the arm to your DC Motor.

You may need to counterweight one side of the ruler/arm to prevent vibration; an old 9v battery is suitable. To check you have counterweighted the arm correctly turn the project on its side and the arm should balance out parallel to base. If one side falls then you need to adjust your counterweight.

Testing

Connect your LEDs to your Arduino using your newly created LED interface board, Plug the interface board in so that the terminal strip connects from pin 2 on the interface board.

Use the LED_Test code to test that the LED’s are firing correctly. LED_Test.pde

The LED_Test program simply cycles through each inpidual LED so that you can check that everything is working correctly.

Displaying a Message

If the above test has been successful then you are ready to display your first message.

Try loading the POV_Banners.pde sketch into your Arduino.

I made use of the character generator by DanielJA (nice simple concept)

Improvements to be made…

The addition of a hall sensor would allow me to steady the text and control the scrolling and prevent it scrolling backwards but unfortunately that is going to have to wait for another rainy weekend.

3 comments

  1. Kevin Harbour /

    Hi Glenn

    I have build ur persistance of vision project. My problem is that the text is very unstable. It basically rotates all the way around. How could I stabilize this.

    Regards

    Kevin

    South Africa

    • Glenn Challen /

      Hi there Kevin,
      I think I was lucky. I used a Tape Recorder motor which seems to have a fairly stable speed once it is running. If your motor is varying in speed then I would suggest fitting a hall sensor so that you can time your message start based on the position of the rotation. I had intended to do this with ine but once it was running I managed to get it stable by fiddling with timing.
      I hope this helps 🙂

      Cheers

      • Kevin /

        Thanx Glenn

        I have decided to use a 555 pwm motor controller to controll the speed of the motor. I think I saw it been used on another pov project.

        Thanks again

        Kevin

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