Introduction: LED Cube 4x4x4
64 LEDs makes up this 4 by 4 by 4 cube, controlled by an Atmel Atmega16 microcontroller.
Each LED can be addressed individually in software, enabling it to display amazing 3d animations!
8x8x8 LED cube now available, by popular demand:
Step 1: What You Need
- Basic electronics and soldering skills
- Know how to program an AVR microcontroller - I will not cover that in this instructable.
- Protoboard. The type with copper circles.
- Atmel AVR Atmega16 microcontroller
- Programmer to program the Atmega16
- 64 Leds
- 2 status leds. I used red and green. (optional)
- Max232 rs-232 chip, or equivalent.
- 16 resistors for leds. (100-400ohms) will get back to this.
- 2x resistor 470 ohm. for status leds
- 1x resistor 10k
- 4x resistor 2.2k
- 4x NPN transistor BC338 (or other transistor capable of switching 250-ish mA)
- 1x 10uF capacitor
- 1x 1000uF capacitor
- 6x 0.1uF ceramic capacitor
- 2x 22pF ceramic capacitor
- 1x crystal 14.7456 MHz
- 2x tactile button
- optional pwr switch
- connector for 12v power
- optional connector for 5v power
Step 2: Multiplexing
How to control 64 LEDs without using 64 individual wires? Multiplexing!
Running a wire to the anode of each led would obviously be impractical, and would look really bad.
One way to get around this, is to split the cube into 4 layers of 16x16 LEDs.
All the LEDs aligned in a vertical column share a common anode (+).
All the LEDs on a horizontal layer share a common cathode (-).
Now if i want to light up the LED in the upper left corner in the back (0,0,3), I just supply GND (-) to the upper layer, and VCC (+) to the column in the left corner.
If i only want to light up one led at a time, or only light up more than one layer at the same time.. this works fine.
However, if I also want to light up the bottom right corner in the front (3,3,0), I run into problems. When I supply GND to the lower layer and VCC to the front left column, I also light up the upper right led in the front (3,3,3), and the lower left LED in the back (0,0,0). This ghosting effect is impossible to workaround without adding 64 individual wires.
The way to work around it is to only light up one layer at a time, but do it so fast that the eye doesn't recognize that only one layer is lit at any time. This relies on a phenomenon called Persistence of vision.
Each layer is a 4x4 (16) image.
If we flash 4 16 led images one at a time, really fast, we get a 4x4x4 3d image!
Step 3: Making the Cube, Template
To get 4 perfect 4x4 grids of LEDs, we use a template to hold the them in place.
I wanted to make the cube as easy as possible to make, so I chose to use the LEDs own legs as much as possible. The distance between the lines in the grid was decided by the length of the LED legs. I found that 25mm (about an inch) was the optimal distance between each led (between the center of each led that is!) to enable soldering without adding or cutting wire.
- Find a piece of wood large enough to make a 4x4 grid of 2,5cm on.
- Draw up a 4x4 grid of lines.
- Make dents in all the intersects with a center punch.
- Find a drill bit that makes holes small enough so that the led will stay firmly in place, and big enough so that the led can easily be pulled out (without bending the wires..).
- Drill the 16 holes.
- Your ledcube template is done.
Step 4: Making the Cube, Solder the Layers
Create a layer:
- Put in the LEDs along the back and along one side, and solder them together
- Insert another row of LEDs and solder them together. Do one row at a time to leave place for the soldering iron!
- Repeat the above step 2 more times.
- add cross bracing in the front where the led rows are not connected.
- Repeat 4 times.
Step 5: Making the Cube, Connecting the Layers
Now that we have those 4 layers, all we have to do is to solder them together.
Put one layer back in the template. This will be the top layer, so choose the prettiest one :)
Put another layer on top, and align one of the corners exactly 25mm (or whatever distance you used in your grid) above the first layer. This is the distance between the cathode wires.
Hold the corner in place with a helping hand and solder the corner anode of the first layer to the corner anode of the second layer. Do this for all the corners.
Check if the layers are perfectly aligned in all dimensions. If not bend a little to adjust. Or re-solder of it's the height distance that's off. When they are perfectly aligned, solder the remaining 12 anodes together.
Repeat 3 times.
Step 6: Choosing Resistor Values
There are two things to keep in mind when choosing a resistor value for your leds.
1) The LEDs
2) The AVR
The AVR has a maximum combined current rating of 200 mA.
This gives us 12mA to work with per LED.
You also don't want to exceed the maximum current your leds are rated to.
I used 220 ohm resistors on my cube. This gave me about 12mA per led.
Step 7: The Controller
The circuits controlling the led cube is described in the attached schematic image.
The RS-232 interface is optional. and can be omitted. That is IC2 and all the components connected to it. Future firmwares will enable PC communication..
Start by laying out all the components on you circuit board in a layout that enable all the components to connect with a minimal amount of wires. If everything fits, solder the circuit.
I won't give any more instructions on this, as the circuit probably will look very different from cube to cube, depending on the size of the circuit board etc..
Information on how to wire the cube to the controller circuit is in the next step.
Step 8: Wire Up the Cube
Pictures explain this better than words. Please see the pictures.
Step 9: Compile and Program
You now have a led cube. To make use of it, it needs some software.
I have made a driver for rendering a 3d data space on the cube, and functions to display some cool visual effects on the cube.
You can use my code, write your own or build on my code and make more effects.
If you make your own effects, please send me the code. I'm eager to see what you guys make!
To compile the program. Just open a command promt,
enter the directory with the source code
type "make" on the command line.
If you want to use an ATMega32 instead of the ATMega16, just change the mcu setting in the Makefile and recompile (type make). If you use the m32 and don't do this step, the cube won't boot properly (the red and green lights will keep blinking forever).
You should now have a file named main.hex in the source directory.
The next step will show you how to get that code into your cube.
Step 10: Program the Microcontroller
To program the microcontroller, I use avrdude and the USBTinyISP programmer.
First off, Let's just see if we can make contact with the AVR.
Connect the programmer to your cube and your computer.
The command is "avrdude -c usbtiny -p m16", wherer -c specifies the programmer, and -p the AVR model. You can see the output in the images below.
Now, upload the firmware: "avrdude -c usbtiny -p m16 -U flash:w:main.hex".
By now, the cube should reboot and start doing stuff. It will be running at 1mhz (very slowly) using it's internal oscillator. And some of the leds won't work, because some GPIO ports are used for JTAG by default.
To enable the external oscillator and disable JTAG, we need to program the fuse bytes:
run "avrdude -c usbtiny -p m16 -U lfuse:w:0xef:m"
and "avrdude -c usbtiny -p m16 -U hfuse:w:0xc9:m".
Be carefull when doing this step! If you get it wrong, you can permanently destroy your microcontroller! If you are using another microcontroller than the ATMega16, be sure to read the datasheet carefully before changing the fuse bytes!
After writing the correct fuse bytes, the cube should reboot and start operating at regular speed with all leds operational.
Enjoy your new cube :D
Step 11: Go Large - 8x8x8
You can find the 8x8x8 version here: https://www.instructables.com/id/Led-Cube-8x8x8/
Please rate this instructable if you like it! :)
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