Idea for regular fairy light controller

[Imstevil]

Hey all, I previously had big ideas on doing a big light display using RGB Pixels, music, etc, etc, etc. Unfortunately money, power requirements, and network capabilities are just not going to make it an option for me at the moment so toying with the idea of making my own controller just for standard fairy lights. Had a couple of questions for anyone who may have tried this already, though I think this may be benethe people in here with the awesome setups I've seen!

One big problem I have is I know enough to be dangerous, but not as much as I should. I'm aware of this so feel free to correct me in anything I say, it's the best way to learn!

Basically I'm thinking of making up my own PCB and and having 4 or 5 H-Bridges on it, and have a spot to plug in a ESP826 to control them and using this to control my fair lights. I'm thinking of making multiple of these that can talk to each other via wifi and store a show on the chip (super basic one, just something to keep the house in sync) I'm thinking I'll have a master controller which will either be another ESP or just running on PC. It would broadcast using UDP a count down leading up to when the "show" should start, which I would use to try and get the different boards as insync as possible. I've attached a PDF of a rough design of what I was thinking of for the PCB.

What do people think of something like this, would it possible or something already out there to work similar? I currently have a very large house with 1000s of leds, hoping something like this might give me SOMETHING to work with until I can afford a proper setup. If it would work...

Another questions which might show I know just enough to be dangerous... is it possible to cut up fairy lights into shorter lengths? I tried cutting down an old string for testing and the more lights I cut off the more power it tried pulling from the power supply until it got to the point it over loaded. I currently have a 75m strand I run around our windows, If I was plugging into a controller I'd like to cut this strand into multiple shorter ones letting me light up windows individually. I did very limted testing and it was on a very cheap and old set of lights, but would love any tips on advice on doing this.

Sorry if this isn't the type of thing discussed here, figured I'd throw it out there as I imagine something this has been done before but very hard to find anything searching for it.

 

[AAH]

My DMX2-18, DMX2-24 and 2811DC2-30 all use a similar sort of H-bridge arrangement to control those evil fairy and icicle lights. The control isn't quite as simple as turning on 1 output or the other as to get both halves of the string to be on you need the dimming signal to be multiplexed with something like a 50hz clock signal so that you have independent control over each half of the string (typically every other led) and the switching is fast enough that there is no noticeable flicker. I originally made the dmx2-18 years ago when this style of 2 wire 2 channel lights appeared as there was nothing around that gave computer control of them. I then had an enquiry from someone who wanted to control thousands of strings and I made the 2811dc2-30 which used ws2811 pixel data and used the dimming of 2811 pixels to provide more outputs at a reduced cost and gave the ability to have up to a few thousand channels hanging off 1 pixel data line rather than 512 channels off a dmx data line. The most recent of the 2 wire 2 channel boards that I made is the dmx2-24 which has a few more outputs than the dmx2-18, has dipswitch address setting and has 2 features that are specifically there for noobs to computer control. There is a "classic" switch on the board which allows all 12 outputs to operate on the same function at the same time. There is 9 (from memory) functions the same as the classic controllers that come with the lights. You can parallel or connect extra lights in series to use more of the current capacity of the board.
Yes you can shorten and lengthen the light strings. David_AVD from the ACL forums has a post on his site about how the lights work and how they are wired. The lights are commonly is groups of about 8 in series grouped with another 8 that are of the opposite polarity. If you don't mind doing some soldering about the easiest way of working out how many leds are in series and parallel is to find somewhere a few leds into the string that has 1 wire into the led and 1 wire out. If you cut 1 of the wires you will lose x leds and you will see where the segments break up.

 

[Imstevil]

Thanks for the speedy and helpful reply, I was aware that this wouldn't give me the ability to light up the entire strand (unless it was the 3 string version, to be honest I have never even seen one of them in the wild!) it did work to a certain extent but like you said would def need a clock to control it to get it looking half decent and not giving off a flicker.

Had a look at your boards, they are pretty impressive! I'd never ask as this is your design and you sell it for money, would have been interesting to see your schematics and see how far off the full design in my head is from yours. Think I'm not to far off the mark, but looks like you're using an Atmega chip instead of ESP? Mine is pretty cut down obviously as I'm not using the 2 RJ45 ports, it's somewhat relieving to know I'm on a similar track to someone who knows what they are doing though!

Think I found the page you were talking about for cutting up the strings:-

2-Wire LED Strings – da-Share

www.da-share.com

Reading that I possibly can't cut them up as I was hoping, as he states

"I could not find any current limiting resistors in this string.

Since all 10 sections are wired in series, you can’t cut them up and still use them on the same voltage."

I'll have to double check my strands, but I'm fairly confident most of them are the the regular LEDs not the bi-directional. I could probably calculate the resistance needed and add my own resitance at the end. It's not as easy as cutting and terminating the strands at what ever length I want from what I can gather though.

Thanks for the reply and information, it gives me some info an ideas to move forward, and have your boards as a back up if I can't get my system working with wifi.

 

[AAH]

Thanks for the speedy and helpful reply, I was aware that this wouldn't give me the ability to light up the entire strand (unless it was the 3 string version, to be honest I have never even seen one of them in the wild!) it did work to a certain extent but like you said would def need a clock to control it to get it looking half decent and not giving off a flicker.

Had a look at your boards, they are pretty impressive! I'd never ask as this is your design and you sell it for money, would have been interesting to see your schematics and see how far off the full design in my head is from yours. Think I'm not to far off the mark, but looks like you're using an Atmega chip instead of ESP? Mine is pretty cut down obviously as I'm not using the 2 RJ45 ports, it's somewhat relieving to know I'm on a similar track to someone who knows what they are doing though!

Think I found the page you were talking about for cutting up the strings:-

2-Wire LED Strings – da-Share

www.da-share.com

Reading that I possibly can't cut them up as I was hoping, as he states

"I could not find any current limiting resistors in this string.

Since all 10 sections are wired in series, you can’t cut them up and still use them on the same voltage."

I'll have to double check my strands, but I'm fairly confident most of them are the the regular LEDs not the bi-directional. I could probably calculate the resistance needed and add my own resitance at the end. It's not as easy as cutting and terminating the strands at what ever length I want from what I can gather though.

Thanks for the reply and information, it gives me some info an ideas to move forward, and have your boards as a back up if I can't get my system working with wifi.

As a most basic design all you need to do is gate the 2 signals going to the h bridge through a NOR gate or similar. This could be done internally in an ESP device I should imagine. I use some fairly low spec PIC micros and have never actually used any of the AVR/ATmega range of processors. It's been on my to do list for about the last 2 years to play around with some ESP stuff as they are incredibly powerful for the price. For the 2811dc2-30 the micro does nothing except provide a 50hz clock as the 5 pin sot-25 package was about the smallest way I could get a 50hz clock. The 2 dmx boards have the dmx receive logic etc in them as well as the test and classic mode code.

 

[Imstevil]

Thought I saw an atmega on one of your boards, I must have been wrong!

Yes, I was planning on using the ESP for all my logic. My thinking here is my shows will be stored on a main computer and sent to individual controllers and stored on their EEPROM. I'm thinking 4 bytes per action, 1st byte the action to take (turning on which strand, and which channel on that strand) 2nd and 3rd bytes are start time, 4th byte how long that action lasts. I'd load things into RAM when actually running the show obviously, but if it's stored internally then I don't have to worry if we lose power, and don't need to constantly send data to the controllers. I have never tested reading / writing large amounts of data like this so not sure how that will go, worst case scenario it'll be falling back to sending the data to every controller before a show starts. I would imagine you would only be looking at maybe 10kb per controller max since it's pretty limited in what it can do.

So using the ESP I just read through the shows, and use the outputs to power toggle the h-bridge states. For me it made sense to do it this way when I have controllers a long distance away with no ability to chain them or run cat cable between them. Could be a better / more elegant solution to this, in fact I'm sure there probably is, it's the best I can come up with my knowledge level at the moment though.