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elektrohase - an illuminated, rabbit shaped whatever
elektrohase is a project which i did in spring 2005. two close
friends of us, Erik and Doreen, married on 9th of april, 2005.
because they had two nifty rabbits jumping around in their flat
at this time, we decided our wedding present for them must have
something to do with those rodents.
a video is also available.
check the link section at the bottom
of this page.
as i'm a bit crazy about electronics (and Erik is too), soon the
idea came up to somehow funk up a rabbit. we need an electronic
rabbit! the plan was to use many many leds of different colors
to illuminate the wooden rabbit. colors were chosen to be bright
red and blue, and to keep the project at a reasonable level, the
number of leds was reduced to 64. in fact i then used only 63 of
them, otherwise two leds of the same color would have been side
by side. the "eye" of the rabbit caused that, you will
see it on the photo to the left (click on it to enlarge).
the electronics itself is rather quick and dirty (i did not have much
time). it uses a atmel atmega8 controller. at the bottom of the
page there is a link to the schematic if you want to have a look.
for the atmega8 circuit there's nothing special. i just left out
the crystal, because the internal 8 mhz oscillator is more than
enough for what i wanted to do here. i added a small reset network
as well as a connector for in circuit programming. if you have a
look at the schematic, you will notice, that the atmega8 lacks of
enough pins to drive all the 63 leds. i got around this by using
serial shift registers (74HC594D) for getting 63 outputs. in fact
i used only the SPI, which is PB3 (serial output), PB5 (serial
clock) and PB2 (shift register clock). the SPI is clocked with
4 MHz. this allows for very very quick updates of all those leds!
because the 75HC594D do not deliver enough current to drive eight
leds each at full power, i decided to pump up the thing a bit by
using some ULN2003AD. they can deliver up to 500 mA per channel.
this is enough for even driving lamps instead of leds! anyway i
put all those components together on a pcb and soldered a lot of
wires to each of those leds. a big battery pack was added behind
the rabbit shape. it was enough to drive the circuit for many
hours during the wedding and even the days after.
now the fun part of this could start: the software! the full source
code you can find along with some other files in the
link section at the bottom of this page.
the code is written in C. i used
WinAVR for compiling
the code on a windows system. there's not much to say about the
code - it's pretty straightforward. i used the builtin SPI module
of the microcontroller to send out the bytes for the shift registers.
this is done in function SetLED(). everything else is just defining
some nifty patterns and then calling them with different parameters
from the main function. have a look for yourself, it's no real
magic inside :)
downloads
here you can download some files associated with this project:
video (full) (divx 320x240, 1 min 48 sec, 6.5 mb)
video (short) (divx 320x240, 17 sec, 1 mb)
video (small) (divx 160x120, 17 sec, 294 k)
sourcecode for elektrohase (language C compilable with WinAVR)
 schematic for elektrohase (pdf 115 k)
PCB top layer (pdf 400 dpi, 37 k)
PCB bottom layer (pdf 400 dpi, 23 k)
component placement (pdf 46 k)
PCB via positions (pdf 42 k)
 schematic (cadsoft eagle schematic, 291 k)
board layout (cadsoft eagle board, 76 k)
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