AN #128 - Moving LED messaging Waver with BI-colour LEDS


This application note is written by Walter Miraglia

Note : This is a great project for beginners. With little hardware and a relatively small program, you can create great visual effects. Since the 90S2313 is used, it will work with the free DEMO too.

LED Messaging Waver ( using persistence of Vision to create letters and words)

The circuit consists of LEDs tied from the 7 pins of portd to the first 7 pins of portb. The remaining pin (portb.7) can be used to switch to different messages or change colour.
This pin is connected to a button with a 10K pull up resister to +5V and a micro switch to GND. (not shown on this schematic)

All the LED's are Bi coloured green and red. There are 7 in total.
The circuit and PCB are published with permission from avrcircuits.



This works best if the display is spun in a circle or waved left and right. The flashing LEDS when moved left and right will create the illusion of floating letters in the air. This is known as persistence of vision.

When waving the display right and left the message is displayed forwards then backwards on the back swing. If rotated clockwise the message remains correct. With perhaps some timing changes or a mercury switch that detects forward motion only, the message can be turned off when swinging back. any takers? I will look into this.



When waving the display with your hands to the right the words are displayed correctly as you swing back to the left..the letters are displayed reverse.


If you are spinning the display in a circle clockwise the display should read correctly.... have fun with it... Bring it a rave and wave it around with your personal message.
The LED's should be as close as possible so the words do not appear to "dotty"

The above pictures were taken with a digital camera in a darkened room.

The included BASCOM-AVR program uses an AT90S2313 Atmel chip program will display two sentences one in green and one in red. The messages used in the example program consist of a 7X7 matrix .... but it could really be 7 vertically by anything..because values are calculated vertically.

Please refer to the table below for the whole alphabet.

This table is copied with permission from Colin MItchell. His site is called http://www.talkingelectronics.com



Here is a picture of the one I built on a perf board. Included in the zip file are all the images as well as a PC Board layout in Eagle 4.09.



The BASCOM-AVR programs are used to display the messages on the LEDs. Please note using the above table you can make it display what ever message you like. You can even do graphics if you like. I built a similar one using 8 red LEDs from portb to gnd that allowed me an 8 X 8 matrix for graphic characters and letters.

Download source code and files in an128.zip