I need to make a thing out of LED lights. I have questions.

December 12, 2016 1:30 PM

So, I am working on a costume build, and I kind of . . .blithely assumed I could do what I wanted and now I am, of course, realizing that I'm slightly out of my depth. I have tried googling but I'm not sure I'm looking at or for the right things. HALP?

I am making a skirt for a performance, and the person has ordered three strands of LED lights (these ones). Ideally we want to be able to turn all three strands on at the same time with one switch. I am not afraid of doing a little electrical work, but I can't seem to google well for this.

Three strands, six coin batteries in all, and one flick of one switch to turn them all on. Point me in the right direction.

posted by Medieval Maven to Grab Bag (9 answers total)

I would tape the three controllers together, in a line. And then tape/glue a toothpick to the three switches.

If you want to get into it, you can try attaching all three leads to the same point in one of the controllers. Requires a bit of soldering, i suppose. Alternatively you could splice the out of one controller to each lead of the three strands with two small wire nuts. LEDs don't draw that much, the two single coin batteries might suffice.

Otherwise you're looking at stacking the coin batteries physically and/or electrically. I figure that's what you've found so far.
posted by humboldt32 at 1:44 PM on December 12, 2016

There are A LOT of tutorials on Instructables.com about connecting or working with LED strip or string lights. I find the site more useful for me than YouTube tutorials. The mix of words and images just works better for my learning style.
posted by Cranialtorque at 1:45 PM on December 12, 2016 [2 favorites]

I think a switch like this would work for you.

Cut one strand of your lights a few inches the battery box, solder one of the cut ends to one of the terminals on the outside edge of the switch. Solder the other cut end to the terminal in the middle of the switch just above the spot you soldered. Repeat for the other two light strands. Leave the switches on the battery boxes on all the time (maybe put a piece of tape over them).

Switches use a weird terminology to show what they do. The switch I linked to is a 3PDT. Which means you have three switches internally that are controlled by the flip of the toggle.
posted by gregr at 2:17 PM on December 12, 2016

Best answer: The pair of 3V coin batteries is connected in series (i.e. + of one to - of the other) meaning that it takes 6V to power the strand. The way LEDs work, they're looking for a particular voltage (6V in this case) and the more current there is available, the longer they'll run for. So you could use one battery pack to run all 3 strings, but they might be dim or run down the battery quickly.

To do that you'd connect the strings "in parallel", meaning stack up all the battery packs and the pair of wires, clip off all the left-hand wires, strip the plastic back to expose the metal wire, and twist the three left-hand wires together, and solder than to the left-hand wire of one battery. then the same with the right hand wire, attach the bundle of the right-hand wire of all three strings to the right-hand terminal of the one battery. If you wanted a remote switch, you'd get a switch with 2 wires coming off it, and attach that in between the battery and the bundle of wires. (you could do that on either the left or the right side).

Now, to overcome the issue of the battery power, you've got one of the other battery packs with two wires coming off it. If you connected the same way you did the switch, one wire to the right-hand battery output and one to the righthand bundle of lights, you'd get a 12V power supply, but all you want is 6V, so don't do that. Instead, bundle the left-hand wires of all the battery packs together and connect that to the bundle of lefthand wires of the light strings, and the same on the right. So now it's kind of like you haven't done anything, you've got all the batteries bundled together powering all the strings - what you've accomplished is to create a single circuit instead of 3, so that it can be switched by a single switch.

Note - am 98% sure that I'm thinking of this correctly and 90% sure that I didn't swap any words around in the explanation, but I don't swear to it. If you don't have $10.98 to buy another 3-pack of lights if this fails, you might want to find some on-site expertise.
posted by aimedwander at 2:19 PM on December 12, 2016 [2 favorites]

Best answer: Aimedwander has it. I work a ton with all different types of LEDs and its' super simple and easy. Just make sure you keep positive wires with positives and negtives with negatives in this case.

Cut all the wires a few inches from the battery packs (to give you room to work with), strip to expose them on both sides, and twist together all the negative wires form both battery side and light strand side, then do the same to the positive wires. I highly recommend soldering, since it's super easy to do, but if not, there is some liquid electrical tape stuff you can coat the wires in so that they stay together and so that the negatives and positives don't touch and short out. Or wrap very tightly with electrical tape (in a color to match the outfit, of course).

If you only need an hour or so of light, you can probably splice all three strands onto just one battery pack the same way. I'd test this beforehand, though, you can always add back on the battery packs as needed.
posted by newpotato at 2:44 PM on December 12, 2016 [1 favorite]

if it were me, and the turning on/off of the lights happens off-stage, then i wouldn't bother making them share a single switch. i am confident with electronics, but it seems like a lot of fuss that's (1) not necessary and (2) could make things less reliable (especially with electronics that are worn, and so likely bent and stressed).

also, after staring at that amazon page in confusion for 10mins or so i think you may be getting 6 strips of lights, if they ordered 3 packages. it looks to me like each package contains two strips.
posted by andrewcooke at 2:50 PM on December 12, 2016

Response by poster: Thanks, this is all helpful. I did find some instructables stuff, but I wasn't sure I was finding the RIGHT things, since I half remember a lot about electrical work from school. The desired result is that the lights can come on on-stage, so turning them on off-stage is not really an option. This is great! Any other tips appreciated.
posted by Medieval Maven at 4:50 PM on December 12, 2016

The picture of the box in that listing says one set of batteries lasts 24 hours, so you should be able to get 8 hours out of one battery pack driving three strings of lights hooked a la aimedwander's description. Doing this with just one battery case gets you one switch.

I'd guess that somewhere in the circuit is a current-limiting resistor. It's tough from the pictures but I'd expect to see it in the battery case. You might find that wiring them up per the above description with just one battery pack drops the brightness. If so add more battery packs back.

Also, I believe you could wire these end-to-end (rather than "connecting all the lefts and all the rights" in one place), if that makes your costuming easier. You still need to match the polarity, but you won't burn anything out if it's backwards - just switch them.
posted by achrise at 6:18 PM on December 12, 2016 [1 favorite]

Best answer: My best DIY electrician advice (for people without tons of electrical supplies) is to do your soldering, then coat the joint in hot glue as a tug-resistant insulator.
posted by aimedwander at 11:29 AM on December 13, 2016