Column: Electronics design
shorts. To do this I connected long lengths of wire to the 5V power supply; at the end of one of the pieces of wire I soldered the larger of my two resistors used on the driver board from Port 1, which allowed me to drive all the LEDs without risk of damage. With a metal ruler, by pressing against
the unconnected common leads, I temporarily shorted all the common pins together to ground, which meant only having to test each anode column once rather than each LED individually. I then joined all the panels together.
Once fully assembled, the cube is fairly strong.
Connections I used a Veroboard to connect an ECIO40P16 microcontroller directly to the 5V power supply and create the NPN common driver circuitry. A 5V supply must be used to allow a fairly large current to fl ow without generating any additional heat. T e Flowcode LED Cube component is fl exible so will work with pretty much any microcontroller family, apart from 8-bit PICs since they cannot have arrays larger than 256 bytes in size. T e ECIO40P16 packs a punch for its size, but a standard AVR-based Arduino will also drive the cube. Whatever method you choose of
packaging or securing the control electronics to the cube assembly, remember to add a hole to allow your power supply to be connected. Some of the popular SMPSUs (Switch Mode Power Supply Units) come in small metal cases, so this could also go inside the box for neatness. You may also want to leave the USB cable connected to the ECIO to allow you to: (a) reprogram without having to re-open the casing, and (b) for communications via USB should you want to go down that route, using the Flowcode USB components to interact with the cube.
Flowcode 6 To create the simulation and the code to drive the display I used the Flowcode v6 soſt ware. I fi rst created a sphere on the panel, making it invisible and then
Figure 2: One method of achieving LED multiplexing is to insert the devices between two buffer 1Cs to which intelligent control is applied
Figure 3: Schmatic of the modular buffer board. Eight of these are required for full implementation of the 8x8x8 RGB colour LED cube
Figure 4: One of eight NPN transistors used to switch 8X8 sections on and off under software control, completing the overall multiplexing scheme for 512 RGB LEDs
www.electronicsworld.co.uk February 2022 13
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