LED Cube Changes for Test

I have decided to scale down the LED Cube to a 5x5x5 in order to test out the timing and construction.  Unlike a lot of LED Cubes that can be found on the internet, I have not had a lot of free time to spend on this endeavor.  Scaling down like this will enable me to at least build a cube with the parts that I have on hand.  Then, as I have some spare time available to me I should be able to test it out fully.  Besides, a 5x5x5 cube only involves soldering 125 LEDs together not the 512 LEDs associated with an 8x8x8 cube.  Aesthetically, it would be more pleasing to have the 8x8x8 or even a 10x10x10 cube but I really don't have the time to devote to it.  This is just for fun anyway.  So a slight change to the connection diagram:




This reduces the MCP23017 count down to 6 or 7, well below the 8 maximum addresses for a single I2C bus.  I will still attempt to do this through one or two Arduinos for control along separate I2C busses.  This structure also means that I will be controlling the Arduinos on one I2C bus from the Raspberry Pi.  So three small computers in the mix.

LED Projector Thoughts

I was contemplating the LED Projector today.  My thoughts from about a year ago was to have some sort of way of projecting LED lights onto a wall or the ground for the purpose of having a Christmas display.  Originally, I was thinking that I could project a series of LED light strings onto a polished cone.  If I were to do that, you could be in a car and pass by the display and see some sort of display in the cone itself.  There would be a radial layout of LED strings on the ground that would light up some sort of scene that would be projected onto the cone and then into the eyes of individuals looking at the cone.  That is a little tricky because of the geometry involved and whether the eye level is in a car, or from someone who is passing on the street (a little higher).

My next thought on the project was to have some sort of hexagonal mirror that could be rotated at a certain speed.  By having a linear string of RGB LEDs you would be able to paint out a scene onto a wall by flashing the LEDs on and off at a specific rate.  There are hexagonal mirrors that are available in laser printers.  I have two old laser printers that could provide these mirrors but I would need to figure out how to control them via a Raspberry Pi or Arduino.

LED Cube Project Revamp

Ok, just ordered 90 more RGB LEDs to do some more testing of the concepts.  This time I am going to interface the RPi through a couple of Arduino UNOs.  The diagram is as pictured:





This shows a bus structure in which the Raspberry Pi interfaces across the bus to the two Arduino UNOs and in turn, the Arduinos interface to the MCP23017s.  I am hoping that this structure will resolve some of the timing issues that I was experiencing last year.

Thinking to get back into the LED Cube Project

Now that I have more time to myself, I was thinking of getting back into the LED Cube Project.  I was also thinking of adding a reflective LED projector to the experiment in order to have something that I can use later during the Halloween and Christmas seasons.  The controls are about the same except that the LED projector would have moving mirrors to reflect an LED strip onto a wall (for instance).  The reflection could also be done to a Conical shaped mirror for use on the lawn.

I have also purchased an additional breadboard to get some of the previous ideas prototyped up and working.  Remember, at last juncture I was unable to get enough control lines due to the chip that I was using running out of address space.

Reworking Some Ideas on the RGB LED Cube

I have not been working on the LED Cube for a while.  Now that I am back to thinking about it, I want to redefine the interfaces from the Raspberry Pi.  I was thinking that a good way of doing this would be to interface to the LED Cube through an Arduino.  I could re-purpose an Arduino to be an I2C device coming in with additional I2C busses going out.  The repetitive nature of flashing the LEDs is ideal for the Arduino.  I could have the RPi formulate the 3D nature of the data points at each phase and have the Arduino take care of displaying the 3D points in the LED Cube.  So the RPi would calculate what should be displayed, relay that to the Arduino, tell the Arduino to start displaying the new 3D point set, and while the Arduino switches to the new data set, the RPi would be busy calculating a different 3D point set.  The nature of our eyesight is that we need to have things change at roughly 1/24 of a second (frame rate) to visualize motion.  That should be easily attainable with the Arduino.  The RPi is better suited to gather other pieces of information.

Electronic Diagram for Portion of Slice 2x2

I decided to put up a portion of the slice electronic diagram to show the connections between the RPi, the MCP23017s, and the RGB LEDs.  This is a 2x2 RGB LED circuit, which in turn is one fourth the size of the 4x4 test slice that I have been using.  The main thing to note is that this is scalable.  At each level of the slice, the anodes of the LEDs are tied together, in each column, the Reds are tied together, etc for the LEDs.  There is one PNP transistor per level to allow current through and there are three NPN transistors per column to control Red / Green / Blue respectively.