The Controller

The Controller

I decided from the start that the controller would be a Raspberry Pi since I have used a few of these around the house including a garage door opener. I bought the latest version which is the 3 B+. If it was a school report card, version B+ would be less than A, but actually B comes after A so B+ is the latest!

I bought the RPi 3+ and 8Gb micro SD card from eBay.

Some device is needed to interface to the pixels. Many people use Falcon controllers. I understand that these are straightforward to use however they are a little more expensive than I had in mind for my first year's display. Instead I used a cape (daughter board) which plugs into the RPi, specifically the Hanson Electronics RPI-28D+ (http://www.hansonelectronics.com.au/product/rpi-28dplus/). It is remarkably inexpensive and it can control two separate WS2811 strings with different voltages. It can also control another string with WS2801 but I didn't need that facility. It can power the RPi from the pixel supply so a separate power supply for the Pi is not needed.

Network Connection

I extended my home network to the controller by running a Cat6 cable to my garage where my controller was to be located. I bought the cable from Bunnings as I find the quality of the cables on eBay to be generally poor.

Many people use Wifi but I found the signal to be weak and unreliable at that location because it is a long way from my modem. Also I found that a power line carrier system didn't work at that location.

Power Supplies

Now the maths starts...

Calculating the size of each power supply... each colour in each pixel requires up to 20mA (0.02A) which means if all 3 colours (R+G+B) are at full brightness such as when showing white, the total is 60mA. Some guides say 50mA so let's just keep the difference up our sleeves as an extra buffer.

Let's start with the 12V circuit.

100 pixels x 60mA = 6A, which at 12V is 6 x 12 = 72W

5 x floods 9W = 45W

So total power requirement is 117W. Allowing maximum load of 85% to make sure the power supply is not overloaded gives 138W.

I took the view that it was unlikely that all pixels would be at full brightness in white, so I selected a 120W power supply since this is the largest standard size available.

Now for the 5V.

200 pixels x 60mW = 12A, which at 5V is 12 x 5 = 60W. Allowing maximum 85% load gives 71W.

I found that 5V power supplies are quite cheap so I purchased one rated at 150W to give plenty of overhead if I add to the load later.

Meanwell is the gold standard but I opted to save money and used generic PSUs from eBay.

Fuses

According to the calculations above, the 24V circuit can draw up to 120W/12V = 10A so I used a 10A fuse. The 5V circuit can draw up to 71W/5V = 14.2A so I used a 15A fuse.

The RPi and cape take very little power so I used a 2A fuse (could have used less).

Rather than try to connect fuses in-line, I bought the Hanson Hexafuse Board (http://www.hansonelectronics.com.au/product/hexfuse/) from Hanson Electronics which takes standard size automotive fuses. I bought a box of fuses with various ratings from eBay.

Crimp connections

I crimped bootlace lugs onto most of the wires to make them easier to put into terminals. I bought a bootlace crimper (https://www.ebay.com.au/itm/301325808452) and a box of various size bootlace lugs (https://www.ebay.com.au/itm/153215439554) from eBay.

Wiring

The wires before the fuse need to be rated for at least the current rating of the power supply. For the 12V power supply that is 10A so according to the table in the 101 guide the cable should be at least 1mm2 which is AWG17.

For the 5V power supply that is 30A so the cable must be at least 3.6mm2 which is AWG12.

The wires after the fuse need to be rated for at least the current rating of the fuse, so for the 12V wiring that is 10A which according to the table requires a cable size of 1mm2 or AWG17 and for the 5V wiring is 15A which requires 1.5mm2 or AWG15. Easiest just to use 1.5mm2 cable for all the 12V circuits and for the 5V circuit downstream of the fuses.

I had some spare wire already and the rest I bought from eBay.

Terminals

The 12V power supply came with a cable attached to the output so I used terminals to connect it to circuit wires. It needed to be rated at 10A.

The connections from my controller board to the pixels were done through a 50A rated terminal strip.

I bought both the terminals from Bunnings.

Bringing it all Together

Here is the wiring diagram.

And here is what it looks like, using a mounting board made from old bed slats and mounted on the side of the garage, inside, close to the roller door.

Notes on safety

The 240V supply must be connected by a qualified person. 

I notice that the protection against touching the 240V terminals of the 5V power supply is a piece of plastic that is lifted up to connect the wires. This is really dangerous!! Please make sure that a finger-proof barrier is screwed in place (not shown in my photo above).