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first time poster here. I am NOT an electrician and I have limited experience beyond basic wiring and home improvement, so please bear with me and feel free to over-explain. :)

If you've seen the series "Stranger Things", I'm planning to recreate the wall of letters w/corresponding Christmas lights for a Halloween display (reference: https://www.youtube.com/watch?v=MEZnX14qaUc).

enter image description here

I want to avoid using a lighting controller or anything like that due to the complexity and cost. The most straightforward solution I can think of is to get a strand of C9 LED bulbs and:

  1. Cut the wires between each one.

  2. Insert each 26 bulbs in the correct position but with the wires poking THROUGH the wall to the other side.

  3. Extend the wires out and connect each positive and negative to it's own momentary switch.

  4. Arrange the momentary switches on a surface like a homemade keyboard, labeled with the corresponding letter it controls.

  5. Drape another (dead) wire across the bulbs on the front side of the wall to give the appearance that they are connected in a series, just for show.

  6. Connected all the positives and negatives off the other end of the momentary switches together into one positive, one negative lead and connect that to a battery pack (2 AA batteries).

Assumptions (again, amateur here, please let me know if any of this is wrong):

  • Using an inverter shouldn't be necessary for this application since the lights aren't going through a controller, it's a simple one-at-a-time light circuit w/a switch.
  • 2 AA batteries should suffice, since the intended use is to light up one LED light at a time.
  • I want to avoid plugging the lights into an outlet because I'm not comfortable with electrocuting myself, and it seems that LED's can run just fine off of a battery pack.
  • More of a question, what is the most efficient way to merge 26 wires into one? Is there a piece of hardware that can like... crimp them together or something? I would rather not solder the whole thing.

Shopping List

What do think, will this work? Any suggestions and/or improvements? I am thankful for your expertise!

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closed as too broad by JRE, Voltage Spike, Dmitry Grigoryev, Wesley Lee, PeterJ Jul 13 '17 at 13:33

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Eh. Get a string of programmable RGB LEDs. Not only can you turn them on and off, but you can also change their color and brightness. All you need to add is a microcontroller and appropriate firmware. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 19 '16 at 3:51
  • \$\begingroup\$ Only thing is I would like the lights to be C9 style "acorn" bulbs for accuracy to the series, and also I have NO idea how to work with a controller. I don't want to get in over my head. \$\endgroup\$ – Bobby Dragulescu Aug 19 '16 at 3:57
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    \$\begingroup\$ The proper way to do this sort of thing would be to use an led matrix circuit directly connected to a button matrix. This will drastically reduce the number of wires which will (a) allow you align the wires into a string and (b) use beldon 9 conductor 22 awg cable at some distance. Make a PCB with momentary buttons on it. Then you can hide it across the room where your pal is pressing the buttons without anyone knowing. You might find efficent bulbs that are big like the christmas tree lights but the current capabilty of the momentary buttons will be the bottleneck I think. Power using SMPS. \$\endgroup\$ – squarewav Aug 19 '16 at 4:53
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    \$\begingroup\$ Oh and put a wall plug on it but not actually connected so when you unplug it it still works. \$\endgroup\$ – squarewav Aug 19 '16 at 4:58
  • \$\begingroup\$ @IgnacioVazquez-Abrams Please tell me where you found a string of addressable LEDs in a Christmas light form factor (as opposed to a flexi-PCB strip). \$\endgroup\$ – immibis Dec 7 '16 at 4:45
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You have the basic idea down. The only thing about this is that you will need a lot of wire, and 26 switches.

schematic

simulate this circuit – Schematic created using CircuitLab

You could wire the leds to use a common ground wire of the led string.

3V may be too low for full brightness on some of the leds. A 3x AA pack would be better.

You will need a resistor though. Assuming 20mA at 3.3V, you need 4.5V - 3.3V = 1.2V / 0.02A = 60 Ohm. Find the next value up. This would be wired between the battery and the switches.

If you don't want to solder the wires, then you need a terminal bus bar or similar.

An addressable led string would be simpler, only needing coding. Here is an example. It would also allow you to show a message without having to manually hit the switches in the right order. Heck, make it fancy, like add a bluetooth module and control it from a iPhone or Android phone.

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  • \$\begingroup\$ Thanks @Passerby! Noted re: the battery pack. For the terminal bus, I don't need one with 26 terminals, I can double or triple-up on each terminal if I have to, right? How will I be able to tell is 20mA at 3.3V is correct for what I have? Is this a standard measurement? With regards to using the common ground wire of the LED string, you mean to say keep ONE wire connected from bulb to bulb to serve as the negative lead going straight to the resistor? \$\endgroup\$ – Bobby Dragulescu Aug 19 '16 at 4:41
  • \$\begingroup\$ Probably. 20mA at 3.3V is normal for most white leds. You can test it on a spare bulb with that ~60 Ohm resistor. And yes, I mean that. You will have to Rewire it as it is currently in series, but it would mean you need much less wire. \$\endgroup\$ – Passerby Aug 19 '16 at 4:46
  • \$\begingroup\$ Thanks for the schematic, helps a lot! So my only question is, after looking for 60 Ohm resistors, I came up with a slew of different options with different wattages and stuff. Any advice? \$\endgroup\$ – Bobby Dragulescu Aug 19 '16 at 5:13
  • \$\begingroup\$ @BobbyDragulescu keep in mind either way is labor intensive. Rewiring 26 bulbs and making it neat. An addressable led string would be easier. \$\endgroup\$ – Passerby Aug 19 '16 at 5:14
  • \$\begingroup\$ @BobbyDragulescu since only one led is on at a time, that's 1.2V * 0.02 Amp = 0.24 Watts. A 1/4th Watt resistor is barely enough, go with a 1/2W or 1W. A 62Ω or 68Ω are the next size up resistance and the difference won't be noticeable to the eye. \$\endgroup\$ – Passerby Aug 19 '16 at 5:17
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See SparkFun's implementation of this which goes over MANY of the non-obvious details, but it only begins to describe just how much time this required to complete.

https://www.sparkfun.com/news/2181?utm_content=33536116&utm_medium=social&utm_source=twitter

You will spend most of your effort hollowing out the C7 incandescents by carefully cutting the spirals off, wiring the neopixels into each, and gluing them back together onto the sockets. Sparkfun wired this up using lots of 4-conductor wire (hacked USB cables).

Of course, the show took much easier shortcuts, simply using a partition wall and wiring those bulbs to switches. But where is the fun in that? :)

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  • \$\begingroup\$ Unsure why this was downvoted without comment. There are folks interested in replicating the Stranger Things light project, and I liked the best-known, best-documented variant. And in terms of "recreation" it's not immediately obvious to folks that most of the time will be spent re-working the glass bulbs to contain ws2812s -- as Sparkfun's tutorial demonstrates. \$\endgroup\$ – Scott Prive Jun 22 '18 at 1:51

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