Internet is full of POV designs: wall clocks, texts messages, playing with an array of LEDs drawing the image, or just flashing when an image (number o letter) is in the right position.
There are even more exciting examples...
So, that's why I decided to build one, and this article shows the very first rudimentary prototype.
- Build a prototype of a POV message with a PIC.
- The motor is one re-used from an old PC, for the message I use 7 red LEDs, so, 5x7 dots characters can be shown.
- A 9 volts battery is on the rotatory part just to supply the circuitry.
- A 12VDC power supply it is used for the PC motor.
- IR phototransistor for sensing position.
Elektor magazine has built one recently, and as said before, surfing the web you can find many examples. It is quite interesting seeing how everyone solves issues like supplying the propeller, sensing position and so on.
Firstly I tried a 5V motor from an old laptop, but torque was too low, so I used the one shown in the video with higher torque, y also had to reduce the distance between the center of the motor and the piece of circuitry. So, for the next POV version it is necessary reduce weigth.
Other issue was supply the rotatory part, for this prototype a 9V battery is used plus a 7805 to supply the circuitry.
Sensing the position, firstly I thought using an omnipolar hall sensor switch in the propeller and a little permanent magnet, so every time the switch detects the magnet, gets the origin, but for the very first prototype I have used an IR photo-transistor, and a fixed IR LED to get get the origin.
The PIC used is a PIC16F870.
Here below a picture and a video:
Improvements for next version:
- In order to reduce weight: The power supply for the propeller will be 2xAAA battery, then the 7805 can be also avoid.
- PIC will be changed to one with internal oscillator, avoiding XTAL also improves weigth.
- Comercial parts will be used, so it can be easily reproduced.
- Implement sensing position with the omnipolar hall effect switch.
I hope you like the post and it also would be great if anyone wants propose alternatives and improvements.