An Analysis Of The LED CUBE 3x3)

This step largely follows the LED CUBE 3x3x3. We'll need a total of 27 LEDs that will be grouped into three sets of nine. Each set of nine LEDs will share a common connection amongst their cathodes (negative leads). We'll refer to each of these sets as a "level". Each of the nine LEDs on a level is connected to the corresponding LED on the other two levels through their anodes (positive leads). These will be as "columns". To start we'll use a drill to create a jig out of a small piece of scrap wood. The jig will hold the LEDs in place while we solder them. We decided to space the holes around 5/8 of an inch apart (~15 mm) but the exact distance isn't critical. The hole should have a tight fit around the LED. Once the jig is done we're going
You should now have three sets of nine LEDs. Position two of the sets one on top of the other. Keep the distance equal to the spacing already established between LEDs. Once you're comfortable with the spacing you can clamp each set of legs using two clips, one in each direction, to keep the legs firmly in place while soldering. You may need to bend around a LED to get a good connection. Solder each of the nine pairs, one at a time. Do this one more time and you're done with the cube. Place the cube on one side of the the pcb board. Make sure the nine legs are positioned apart evenly while you guide each one through a hole. Our board has five holes between each set of legs. You want to leave as much room as possible on the other end of the pcb board to fit the various components. Add a few clips to hold the legs in place once you're happy with the positioning. Leave plenty of leg poking through the bottom since this will make it easier to solder the resistors later. Turn the board over and solder each of the legs to keep them in place. Flip the cube back over once all the legs have been soldered. Lastly we need to solder a lead from each of the levels down through the bottom of the board. Strip a piece of solid wire and bend a small hook on one end. Fig. 5. Construction of LED CUBE.

Hang the hook on one of the center LEDs legs and guide it through a hole on the pcb board. Solder the hook end to keep the wire in place. Repeat again for the other two
Each of the nine columns will connect to a pin on the Arduino through a current limiting resistor. Each of the three levels connects to ground via a NPN transistor when activated by an Arduino pin. We'll be using 12 output pins total on the Arduino but there are 18 LEDs to power. The trick is that only a single level can be lit at a time. When a level is connected to ground, each of the LEDs on that level can be powered individually through one of the nine other Arduino pins. The first step is to prepare the nine current limiting resistors. We are using 220 ohms per pin which will draw around 22mA. The value may vary depending on the LEDs that are being used but stay between about 135 and 470 ohms. Each pin is capable of sourcing up to