Design & Build Blog – Page 2

Decision 3 – Incorporating Existing Lights

In the world of pixels and programming, it appears from the outside that the legacy light string is left behind. However, due to the crossovers as people were migrating displays from AC based, to DC based, and then to pixels, some special circuit designs were made up. These allow for either DMX or “pixel protocol” based control of DC strings (and in some cases mains rated AC strings).

Older style low-voltage lights typically had 2 or 4 wires to the lights, with a single common (either positive or negative rail). By switching on one of more of these individual lines, a particular colour or segment of the light string would light up. This was a relatively straightforward method of lamp control.

In the mid-2010’s a new style of LED light controller was designed, which uses two wires from the controller to the light set. As LEDs are polarised devices, they will only illuminate when the positive and negative rails are the correct way around. This has its benefits. By alternating the polarity of every second LED, the when applying the voltage one way, the odd numbered – first, third, fifth, etc LEDs would illuminate. When reversing the polarity, the even numbered LEDs would switch on. In order to display all LEDs on simultaneously, the controller is actually reversing the polarity to the string at a rate faster than the human eye can see, giving the appearance that they are all on, when in fact only half is ever on at any one time.

Credit to David_AVD of DAShare for this image [Link]

This method is used in the BigW and Bunnings Lytworx style controllers, as well as many other cheaper designs. This provides a complication, as it’s not simply a matter of switching one, two, or more wires on to enable the colours, but a smart controller is needed.

Which brings me to the crux of this post – is it possible to utilise these style strings within a pixel display – and the answer to that is YES!

A bloke by the name of Alan Hanson (of Hanson Electronics) based in Victoria came up with a circuit design which takes in DMX data (24 channels worth) and can interface with 12 of these strings, providing independent control of both “polarities” within the string. This means that it’s really easy to integrate this in with the display. The product itself is called the DMX2-24 – and I have acquired one for this project, along with a USB DMX dongle

So what this means is that I am able to keep utilising my existing purchases until I’ve replaced them with pixels. Having this board also means that should I ever forgo the basic lights in my main display, I can use it at other premises to provide some animation to existing sets.

I’ll have more information coming in the Technical Experiments section as I play with and learn the device further.

Decision 2 – What types of lights should I use?

There is wide debate on the internet as to whether to use strip lights, or nodes/bullets. To start off with, here is a description of each type.

Strip Lights

Strip lights come on a flexible PCB, with surface mounted LEDs, and often an adhesive backing. These are either WS2812B style (LED and IC in the one package) or WS2811 (where the LEDs are separate from the driver chip). There is a variance on LED density, from roughly 30 per metre, all the way up to super dense at 144 LEDs per metre. 5V ones are generally individually controllable, whereas 12V are grouped into threes, to cope with the voltage differences.
These are able to be cut and rejoined on specific markers, and include the PCB pads to attach wiring for this purpose. They can either be bare PCB, resin coated, or in a silicone tube – each providing increased levels of water ingress protection. In the image below you can see the difference between the different densities.

Bullets / Nodes

Pixel nodes/bullets are individual 8mm RGB LEDs soldered to a little PCB which contains a WS2811 driver chip. It may also include either resistors or voltage regulators on 12V versions to drop the voltage to 5V. They are connected by various lengths wiring – often around 100mm – to the next pixel, forming strings of either 50 or 100 nodes.
Each pixel is encased in epoxy to provide water proofing. These can be pushed into props, held in place with cable ties or various other mechanical holding techniques. The wiring can be cut at any place to add or remove individual or groups of pixels, and rejoined as necessary.
Whilst I talk about bullets primarily here, there are also square nodes, which I am not using to begin with. They have very similar properties to bullets, but are a different shape and slightly different design. The pros & cons below apply to both equally. The image below shows the bullet vs square node type.

Pros & Cons

So – why would you choose one of the the other?

Nodes are much easier to repair than strips, as strips require carefully cutting out the bad section and solding fine pads, and then re-waterproofing the assembly
Nodes can be pushed into props, whereas strip cannot
Nodes are more durable whereas strip is quite fragile
Strip is easier to get in a nice straight line, without loose wiring
Strip provide a less ‘pixelated’ look, and give a cleaner finish once installed

So there are some places where strip is great, and some where nodes/bullets are great.

Can they be mix and matched?

Absolutely! They all use the same protocol, so they can even be part of the same string. There’s nothing stopping you having a line of LEDs which is Strip then Nodes then Strip again.

Decision Time

I’ve decided that I will use bullets for the majority of the props, roof outlines, gutter lines, and mega tree. This is because it’s easier to work with and repair.
However, for the arches, strip will be used as it’ll be encased in plastic tubing, providing protection, and it’ll give a nice even lighting. Additionally, I’m also going to mount strip on the eave to shine onto the house which will provide a nice neat out-of-the-way look.
As for the mini-trees, those have yet to be decided. I have budgeted to do them in either, and I’ll give both a try and see what looks the best and is easiest to manage.

Decision 1 – What do I want the display to look like?

This is the hardest question to answer. I had some clues from looking around various YouTube videos of what others had done, and how I could incorporate aspects into my own design.

A couple of design aspects stood out which I am looking to incorporate in the final show where possible.

Roof outline – Crisp lines bordering the gutters and ridge look great. That was a must. Adding verticals for the columns and edges of the house may come later.
Leaping Arches – The bounce to musical sequences really helps ‘liven’ up the display
Mega tree – A mega tree is always a focus of a display. It grand stands in the yard really bringing attention to itself, and the ability to run a multitude of effects makes them very visually appealing.

Jace (my wife) has been across some of the design and the possibilities, and one deign aspect that she really liked was singing Christmas trees. Additionally, I thought a bit more Christmas look with snowflakes, a Bethlehem star and some candy canes would be nice too.

The next step was to start laying out the design within xLights. This is the software used to program sequences. It has both 2D and 3D capabilities. In 2D mode, you take a photo of your house square on, and you lay on the models. This has limitations when it comes to rendering effects (later down the track) so by using 3D mode, you can offset each item on the Z axis as well.

This is the design that I am working towards.

5 arches spanning across the 5 front fence panels
6 candy canes, mounted on each fence post
3 flood lights to light up the hedge different colours. These might end up shining on the house later, but that’ll be a decision once they arrive.
4 mini trees on the front lawn. These stand about 1.4m high.
Mega tree and a 3′ star on top.
Singing tree on the diagonal portion of the front porch, so it’s visible from the driveway
Bethlehem star over the front entry
Wreath on the door
4 snowflakes, one between the lounge windows, and three on the columns
Window outlines
Roof & gutter outline
House wall lighting
Fence lighting
Palm tree lighting

All of this adds up to a fair amount of effort, but I think it’ll look nice. It’ll also give me opportunity to add further, and each component can be done separately, so that if it’s not ready by year one, it can be used next year.

Planning the Show

A lot of reading has happened in the last month, in addition getting some valuable advice from the folks at the ACL Forums & Chat. This has led me down rabbit holes of research, to figure out the best way to design the show.

A number of questions needed to be answered, with each answer flowing into the next decision to be made.

What do I want the finished display to look like? ie. What props, what effect, what sort of look am I going for?
What types of lights should I use, strip, nodes, etc?
Can I incorporate any of the existing light strings I already have?
How will I control the lights?
How will I distribute power to these lights?
What hardware do I need to make this all happen?
How much will it cost?
What do I need to cull to fit into any reasonable budget?

In early January, I met up with one of the blokes from the ACL website, Kent. He had his first Christmas display up in 2021, so I’m trailing one year behind. He offered many pointers, and showed me his setup – unfortunately I didn’t get a chance to see it in action, but it was great to catch up and discuss things.

Being a lovely bloke, he also lent me a few pieces to play with – 40 odd nodes, an ESP32 controller and a DC-DC convertor. I had also picked up a 2m strip of LEDs from Jaycar in the interim and starting playing around with those hooked up to a Raspberry Pi. Some more technical posts on these will be coming up.

Over the next few posts, however, I’ll discuss the above decision points individually, and explore the answers that I have come up with.

In The Beginning

I’ve always been into Christmas light displays. Various basic light strings here and there, nothing too special. But the last few years I have been very slack.

In early December 2021, my right-hand neighbour put up a nice display, nothing too out there – a few Big W strings on the house, and around his fence. It was also at that same time which I was putting up the Christmas Tree, and getting all the decorations out.

So, I thought, why not put up some of the lights I had squirreled away. Motivation was also driven by the fact that in January 2021, I welcomed my first child into the world, and it would be nice to make something special.

However, I had no such luck, the old lights were all filament strings, and most weren’t working properly. So off to Bunnings, and I picked up 4 strings of lights, three for outside, one for the tree inside.

These came out pretty nice, for the first go – the neighbour on the left-hand side has two kids, 5 and 3, off memory, and they were amazed by the lights, despite how simple it could be.

So – what could I do to make it better? I’ve always been interested in computer driven lights, however where to start? Did I need to write software on an Arduino; build a lighting controller, and do it like that?

This is when I stumbled upon the Australian Christmas Lights forum (ACL). They have a fantastic guide (the ACL101) – which details all the bits you need to do, and consider, for a fantastic display. I was absolutely blown away by the software and hardware already out there to make this happen.

From there, the bug had bitten. I was hooked. The research started.