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August 13, 2007

Arduino POV Prototype

This is my first attempt to create a persistence of vision (POV) display using the Arduino. The ultimate goal is to mount it on my bike wheel and have it display nice things while I ride. But, for now, it consist of an array of 6 LEDs mounted on a turning rig I made From scrap material.

Materials for the rig:
  • 2 old cell phone batteries (found in the garbage) that serve as a counterweight
  • A piece of metal (from an old photocopier) that constitutes the turning blade
  • A fan motor from some sort of broken power supply I found in the UdeM garbage
  • A piece of plastic that makes the base (also from the photocopier)
  • A plastic poster edge (the things used to hold paper posters) that I found in the garbage (it is used to cover the sharp edges of the blade).
  • A heavy metal block that stabilizes the contraption (since it tends to oscillate a bit when it's turning)
  • A cable with a switch from an IKEA lamp I found in the garbage
  • Lots of cable ties
Materials for the POV circuit:
  • A small breadboard (it came with an electronics magazine)
  • 6 red high power LEDs
  • 6 1 k Ohms resistors
  • A 9V battery w/ battery older
I think the pictures are pretty self explanatory.

The LEDs are directly connected to the pins 2 to 7 of the Arduino and their current is limited by the resistors.
The entire circuit is powered by the 9V battery.

So far I have done some simple patterns for the display and I'll upload the code soon (it still needs some polish)

I expect to add more LEDs to the design as soon as I get the patterns and the overall code working fine.


Kevin said...

how do you know how fast the blade turns?
i mean you have to know that so that the leds are on at the same location every turn

Carlos said...

Good question Kevin. I don't really know it. In order to have everything synchronized, I tried many delays and before long I got the pattern nicely in sync (trial and error rules).

The time of one full revolution can be estimated by adding the time it takes to produce a drawring with the time between drawings. I'll upload the calculation tonight.

Anonymous said...

use a magnet and a hall sensor!!!

Carlos said...

A hall sensor would be good, but unfortunately I don't have one.

I plan to use my bike's speedmeter once the POV is mounted on it.

Anonymous said...

You can also use an opto coupling device from an old mouse, simply making a hole. Sure you have an old mouse, don't you?


Anonymous said...

Hey there. I'm trying to do something similar right now. Unfortunately i'm not that good in coding. Did you upload your code by now? It would really help me alot, i initially started this project after stumbling across this blog-entry.


Carlos said...

Diaak, just check the post that comes after this one to get the answer to your question.

ALFONSO said...

Hola Carlos,

tengo un apregunta que hace mucho tiempo me intriga y no sabía a quién preguntar.

En tu proyecto utilisás, para unir los cables, un tipo de "capuchones" de color amarillo, los cuales como que se "enroscan" a los cables empalmados (en tu proyecto, los de color blanco y negro).

Encontré que aquí, en Montreal, es la manera más común de unir cables, y me pregunto si esta manera es tan buena como la de utilizar un "dado" para hacer las uniones.

En mis clases de electricidad, había aprendido que la manera más segura y mejor en cuanto a la conducción, es con los dados.

Llego acá, y me encuentro con que todas las conexiones eléctricas se hacen con esto, y no me parece tan seguro como el dado, que aprieta los cables con un tornillo, esta manera de aquí, como que tiene la tendencia a zafarse.

Tenés idea de por qué, los ingenieros canadienses determinaron que es más útil, o más confiable, el uso de este tipo de dispositivos ?

Carlos said...

Los capuchones no son la mejor manera de unir cables, se pueden zafar fácilmente con un poco de tensión mecánica en el cable.

Es cierto que en Montreal son muy comunes y baratos, y debe ser por eso que todos los usan. Yo los uso para hacer conexiones provisorias rápidas. Si miras un proyecto mas en serio como el excavador lunar, donde me encargué de hacer las conexiones eléctricas, no vas a ver ni un capuchón.

No sé que piensan los otros ingenieros de estas conexiones, pero es cierto que casi todas la conexiones eléctricas en las casas están echas así (con capuchones).

Gracias por leer mi blog y suerte.

Anonymous said...

Hola Carlos, yo hace poco me he comprado una Arduino y esto es asombroso, el mejor proyecto que he visto hasta el momento hecho con Arduino. En que lo programaste? Tienes pensado poner más info para que nosotros también podamos hacer algo parecido? Te comprendo y no creo que quieras desvelar más datos, pero sería maravilloso.


Anonymous said...

perdóname... el "gracias?", lógicamente era un "gracias!"

Anonymous said...

Hi Carlito!
Just found your site and think it's great! I've been wanting to build something like this for ages, and I used your code and instructions to do it. Thanks!

I've written a little flash movie that allows you to build your array data visually, so you can copy and paste the data in, rather than having to type all those little ones and zeros. It saved me a lot of time.

I hope someone will find it useful! It's at my site -> http://gomako.co.uk/main/?p=11

Unknown said...

Hey Guys, check this out.


This Spikenzie guy, has automated the process, i know he sells arduinos, but this POV that he made was using a pic processor.