by Dorty, published
Watch a 4x6 - Matrix on YouTube: http://www.youtube.com/watch?v=DeNzGhN-fe8
This thing is a LED-Matrix ... the Cubes are 8cm x 8cm x 3cm .. the Chip for controlling the LED's is a WS2803 (get them at ebay) .. a WS2803 is a constant-current-led-driver with 18 channels .. meaning with 1 chip you can control 18 leds or 6 rgb leds. Please note a RGB-LED is having different voltages per color ... but the same current ;-) .. so a constant current driver will ensure the voltages are automatically set by the chip .. you dont have to care about that.
Okay .. this tiny Chips are SPI-Controller ... so they have a Input-CLOCK-Pin and Input-DATA -Pin ... AND best of all ;-) Clock-Out-Pin and Data-Out-Pin .. so you can chain this chip with 2 wires :-)
e.g. for the 15 x 6 RGB-LED-Matrix i'am building .. a build 6 Cube-Columns ... every column is powered by one WS2803 Chip which is connected to the next column .. its quite easy to build a giant LED-Matrix with this driver .. please notice .. a LED is max. requiring 20ma so in my scenario i'am using 15*6 Leds => 90 LEDs each LED will require current ;-) so you need a pretty strong power-source (5v @ 6a)
For controlling the WS2803 i'am using a simple Arduino UNO (you can use any other microcontroller you like .. Picunio .. stm32...)
At the Bottom of every column i am mounting a "electronics cube" for the ws2803 circuit .. the cubes are having wiring holes ... one led-mount (you need cooling to get the correct diameter) and a option to use cable ties .... i used a glue gun.
For the WS2803 you ned RGB-LEDs with same ANODE (+)
The WS2803 is a PWM-Driver so you can dim every led with 8 bit (0..255)
*** The photos are showing the back-side of the cubes ;-)
*** Power-Source Notes:
LED[r?] 2,2v 20ma => 0,044 Watt per Channel LED[g?] 3,3v 20ma => 0,066 Watt per Channel LED[b?] 3,4v * 20ma => 0,068 Watt per Channel LED => 0,79 Watt per LED
e.g. 6x6 Matrix => 36 RGB-LEDs (108 Channels)
36 RGB-LEDs * 0,79W => 28,44 Watt + ICs + Microcontroller + Doubled-Security .. Lets say a 60 Watt Power-Source should be fine in this case .. however .. do our own calculations ;-) ..
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Print 6 LEDCubes and clue them together .. Print 1 LEDElectricCube and clue it at the bottom .. Glue a RGB-LED into each LED-Cube .. The contacts can be bent away cruciform. Solder the ANode's of all RGB'Leds together .. Solder all left contacts (18) to the WS2803 .. you should use some kind of order ;-) if make a mistake you should be able to fix it with a simple software based mapping.
You need to connect the WS2803 to the power-source (5v) .. and you need the connect the anode of the leds there to.
You can find some sample code at the end of this thread: http://www.mikrocontroller.net/topic/269588
Doh .. one thing left .. the WS2803 needs to know how much current it should output ;-) so you have to connect resistor from IREF to GND .. most likly a 1400 Ohm resistor for 20ma (read the documentation of the ws2803)
!!! For powering our LED's you will need a seperate 5v power supply !!!