My name is Mark and I’m an engineering teacher at a college in Mandurah WA. A local church has asked me to help them (aka build for them) a Christmas tree such as the one in the attached image. The image is white LED’s only. However if I’m going to the effort of building all this it doesn’t take a lot extra to make it RGB. I have done the structure as per the attached plans, and I’m scratching my head a little with the electronic element. I know enough electronics to be dangerous, but it’s not my forte.
I’m planning to make the triangles out of L profile aluminium extrusion with either acrylic, ply, or shade cloth, inside it. The LED strips will go along the inside of the L. Because the need to bend in the Y axis I need side projection LED’s instead of front. They also need to be waterproof.
I will be using WLED on a Firebeetle bird ESP32-E. And hopefully powering it using the recycled PSU power supplies shown. I will need to get some drop down converters to run the LEDs of the 12v rail but can run some off the 5v.
I have a lot of questions. Can I run these power supplies in parallel or will I need to run dedicated power lines from each PSU to the LED strips it is powering.
How can I connect each triangle to the firebeetle so that I can address each triangle individually. I’d like to run patterns to go across the whole tree in sequence rather than just each triangle individually.
I’d really appreciate any suggestions. I need to order these materials tomorrow at the latest. It gets turned on 8/12 and time is becoming an issue.
Good to have you with us.
Happy to weigh in, I love me a Christmas Tree.
I want to let other people answer on your question about power supplies. My intuition is that as long as it has a common ground everything will be dandy. It also has good specs, but whether it is enough depends on how many LEDs you want to run what type they are.
I do have lots of experience here
I count 6 L strips of LEDs that need to be connected to the Micro controller.
Something like this led strip takes power, ground, data in, and data out. Data out is for daisy chaining but, with the L shapes, you probably don’t want to do that. The firebird has plenty of IO anyway so you can just use pins D2-D9 for each of the strips data in. Ensure that your micro-controller shares a ground with every Led Strip.
This choice means that if you want to do digital patterns you’re going to have to do it with code.
My suggestion:
instead of thinking of them as 6 traingles, think of it as a pizza with six slices. Here I’ve coloured each led strip.
Think in polar co-ordinates. Notice that Pixels on the stem of the yellow led strip are always (k, pi/2) where k larger values of k represent pixels closer to the base. Notice that ALL pixels on the xmas tree’s base have coords (5, 2pi/k)
For example : If I wanted to write a function that did a Mexican wave across the base of my tree the pseudo code might look like this -
while (true) {
for (int i = 0 ; i < numLedsCircumference; i++) {
pizza.clearAllLeds();
Led my_led = pizza.getByPolarCorords(pizza.radius, math.floor(2π/i)); // get led on base of the tree
my_led.colour = Colors.fromRGB(i, 0, 255 - i); // color wave from red to blue
}
}
Some great suggestions/info from @Pixmusix, thanks as always
I heard that you spoke with @Blayden about some of the challenges related to this project, namely the logistics of moving the amount of current you need.
From what I heard, you were hoping to have approximately 40m of addressable LEDs. Typically, addressable LEDs draw about 60mA per unit, thus assuming a fairly standard LED strip count of 40 LEDs per metre, the power draw is as follows:
60mA x 40/m x 40m = 96000mA = 96 Amps
It’s tough to know exactly how much current would be drawn at any given time. The above figure assumes all LEDs are on White at 100% brightness simultaneously, as such the real figure may vary. This also doesn’t take into account the power loss over the circuit’s length, though I believe you have already discussed this stuff with Blayden.
The primary concern from my end, however, are the capabilities of your electrical installations. Residential distribution boxes alone are often only rated for residential current draw, around 100-200 Amps, and that doesn’t include the capability of the actual power delivery cables themselves! I expect you may have more leeway given this is taking place at a church, so it could very well be possible with the current installation, but its hard to say without knowing the premises.
Keep in mind it may also be possible to adjust the method of your project to achieve what you want, if the power requirements become too large of a roadblock.
Looking forward to hearing more about this project, good luck!
What has that got to do with it. That 96A is LED current at LED voltage which probably would be 5V. That equates to 2A AC at the 240V AC level. Even if the LED voltage were 12V the 240V AC current would only be about 5A.
Modified of course by the conversion efficiency of the particular power source used. Unknown at this point.
Cheers Bob
Cheers Bob
Thanks so much for your response! However, I’ve not communicated clearly what my outcome is. If you see the attached photo with the tree that has a series of triangles all over it. 30+ different size and shape triangles. That’s the goal we are working towards.
How would you connect so many individual triangles to the firebeetle, and the program them.
Hi Mark
Just butting here on this side of things
I think a bit more info would be nice (read essential)
How many LEDs are there on each triangle.
And do all the triangles have the same number of LEDs and are they all the same type. It could probably easier if they were. (same number and type)
Is the colour pattern going to be the same for each triangle. Once again easier if they were.
I stress the “easier” bit here as you have a great deal of work to do before you even think about programming LEDs. Unless you have access to a lot of energetic and knowledgeable people you could be stretching XMAS.
There is one way out here if you get too short on time. Build the structure and hang some coloured globes on it on a temporary basis and start on the LED project on Boxing Day for XMAS next year.
I am not trying to be funny here but you have a lot to think about, even your LED power distribution. The data requirement can be a separate entity as long as all the grounds are connected together.
By the way that drawing you provided only indicates 6 triangles. That is what Pix based his suggestion on. Actually there are 18 if you double and triple up on the upper vertical bits.
Cheers Bob
Once I drop it down from 240 to 5/12v I think the current will be fine.
My main question is the configuration of the power supplies. They can each output 17A at 12v which is 40.8A when dropped to 5v plus another 11A on the 5v rail. I’m not entirely sure if it could output the full 50A at one time, so to be safe I have 4 of them. This should mean that each only runs at 50% capacity if all strips are running 100% and white.
How do I join the whole show together. Will the attached diagram work?
Ah yeah I see. I think you’re trying to say that you’re wanting to copy the example photo precisely and then convert it to RGB?
To assist further I’d need to know what LEDs your using
Rob seems to have you sorted on Power.
i Mark.
NO NO NO. You cannot parallel power supplies that way. If you do that you will have to have some pretty big diodes in series with the 12V. Even then the problem of balancing would not be practical for 4. The supply with the largest voltage will pick up most of the load. This will stabilise to a certain extent when that supply sags to match any others but will constantly be stressed at Max current plus.
Break the LED supplies into 4 groups. This will mean 3 more 12 to 5V converters. I assume rom this the LEDs are 5V requirement. I don’t recall any mention of this.
That is a pretty hefty 12 to 5V converter. Your calculations re current @ 5V are not quite correct. Factor in the conversion efficiency (which should be published) . a figure of 85% is common. With this number your current at 5V is 40.8 * 0.85 which is 34.7. You might get a converter with a figure of 90% but I don’t think you will get much better.
Question. Why are you feeding the 5V back into the 12V power supplies.
I just answered that question. Your supplies are 12V and 5V (assumed by re reading previous post) and you are paralleling these together and paralleling the result with the output of the 12V to 5V converter. I reckon that is a recipe for disaster. Start thinking again.
Next question. Why are you using 12V. Much easier to generate 5V in the first place with no converter. Once again I realise now you already have these supplies. Probably ATX supplies out of old computers. Am I right?
Exactly how many LEDs have you got. Pix guessed at 40 per metre. Zac’s figure of 60mA per is pretty spot on. You have to realise that each “LED” is actually 3 LEDs (R, G, B) @ 20mA each. White at full brightness (pretty bright) being worst case.
Your best bet I think would be multiple 5V supplies I mentioned above and load them up with LEDs individually. This is OK. Data line(s) can be considered separately the main thing is all the grounds be connected.
Cheers Bob
Thanks for your help with this one @Robert93820. Re: power requirements you are very correct that it will be stepped down to LED voltage. I was kicking myself upon re-reading that! My brain must’ve taken the day off.
LED count wise, addressable LED strips can range from 30-60/m, as such it is ideal to know which exact strips are being used as the current consumption will drastically change.
I think Bob’s suggestion of individually loading each PSU is the best bet.
Firstly, thanks so much for everyone’s help. I appreciate it so much.
I am using the 60 LED/m side project adafruit 1m led strips on the core electronics site. This will allow me to simple bend the strips around the corners of the triangles rather than cut and rejoin sections.
So I had intended to use the attached conputer PSU’s that I can source for free. Purely because they are free, and also I like to teach my students how to reuse things.
However the goal of making this as simple as possible to take down and set up again next year and for future years trumps this. If I can buy a single 5v power supply that can manage this level of load and number of LED’s, then that is better than creating four seperate circuits and trying to come up with colour systems or other ways of identifying them.
That’s why I’d hoped to be able to connect them so I can create a single power circuit around the tree. If this was a one off install I could do whatever I want, but they need to be able to take it down, store it, and put it up again next year potentially without my assistance.
I’m open to any ideas. How would you do it? Forget my thoughts, what would you do?
A single supply would not be an insurmountable problem. Bear in mind that it is only the 5V supply that would be separate circuits. The data is a separate identity and you can do whatever you had planned for this as long as the grounds are connected. The down side for a single supply is that you will still have to feed your LED string at several points. If you don’t you will have a fairly large voltage drop along the length of the string with the result you will have a gradual diminishing of intensity along the length.
Assuming for the moment you are going to use a single supply. There are a couple of ways to do this.
Feed the 5V into the power connections at several points along your string using heavy gauge cable. This applies to both positive and negative wire as don’t forget the negative connection is part of the high current circuit. As there is only one power supply there is no need to break the power connection through the string, just connect the heavy wire to the connection point. Run separate wires for this to every point from the supply or you will need to use a very much larger wire and you will run into mechanical connection difficulties.
Secondly you could break the power into several groups and connect these in parallel to a single supply.
The other option is to connect each group to its own power supply as has been discussed.
Whatever you do I think you will still have to break the tree into groups for power distribution. Otherwise you are going to have voltage drop problems with subsequent brightness variations. You might get a result with one circuit by using heavy cables of 6 or 10 square mm and branching off this to the individual groups as in option 1 above with smaller wires. At the end of the day this could be your best option and the easiest for dismantling and re assembly.
I think you should get a few options down on paper and think about exactly what you need to do.
But whatever you decide. Carefully and accurately document everything and get others involved in this first effort. That way you might have a chance of having this re established successfully at a later date.
I hadn’t planned to join all the leds in one long string.
The main contender in my mind is something like as follows.
A main 5v (heavy gauge) supply going up the centre of the tree spine. I will put plugs at the joins so the whole setup can be left on the frame when it is broken into its individual segments to be taken down.
Branching off here out to the surface of the tree (where the lights are) at intervals each support will be power.
The tree will be cut into sections (like doughnuts) horizontally and the power will be fed to each loop individually. I’m guessing 4m of LEDs per loop would be close to the max I should try?
The signal wire can be joined together from triangle to triangle across the surface of the tree.
Hi Mark.
Approx how many LEDs per metre. Tis can differ widely with manufacturer. For instance a couple that Core sell are 30 per metre and 60 per metre.
That idea should be OK. Run the main distribution wires in a larger size then distribute to the “doughnuts” in a smaller gauge. As I said the Data circuit can be whatever you want, Just make sure all the grounds are connected.
Actually I am getting a bit confused. It looks like that green connection is 5V power . If that is the case it looks like the “doughnuts” are all connected in series. That is NOT what I am suggesting.
Run the Pos AND Neg in large gauge wire right to the top and branch off that for each section or group of LEDs.
Cheers Bob
I am not going to have much time over the next week. Visitors from Queensland. But will monitor and do my best.
I will attempt to make my triangles either 1m or 2m perimeter to avoid needing to cut and join these strips, but there may be some that or oddly sized.
If I joined all the signal control wires in one long LED string, but powered them individually. Does this mean it would only take two I/O’s on the board? Because if I power each triangle individually there won’t be enough places on the board?
That’s a great question.
Never needed to but based on what i understand about neopixel protocols i think that will work @Zach can you confirm of I’m right or wrong?
If youre connecting all of the data lines together then i suppose you only need one for the data input of the start of the chain.
There isnt a limit to how many leds you can control with a single IO but, based on this github issue, you might run into frame rate problems. If you dont need to syncronize to anything, like music, that probably wont matter to you.
Hi Mark
Just what you do with the Data line depends on what sort of light patterns you want or what you want the LEDs to do. I don’t know of any limit on the number of LEDs on any one string but Pix seems to say there is none. But if you have 40 Metres that is 2400 LEDs. I have a commercial controller here that has a limit of 800 LEDs but that is probably the controller itself imposing that limit.
Anyway Pix is correct, if you only have one string you will only need 1 GPIO pin. Even if you have 2 strings doing exactly the same thing (with the same number of LEDs) and the same patterns you can connect them both to the 1 pin in parallel. I have that situation here where I have 2 X 5 metre strings (150 LEDs each) connected in this manner. The data input is high impedance so one output pin (Arduino ProMini) handles this OK.
Cheers Bob
