Halloween LED Jellyfish Costume




About: I am interested in the boundaries between engineering and art, with a slightly eco/nature vibe.
EDIT - I'm actually selling this costume now as I need space back! details on my blog http://www.deadinsect.co.uk

This is a visually stunning fancy dress costume using LED rope lights and a plastic washing basin to create a deep sea bioluminescent jellyfish thing.

Perfect for Halloween, or any party where it's going to be dark. People will stop in their tracks to start dancing round you, or simply have a spasm. You will feel like a total attention whore, but you will love it too.

Step 1: Summary

You are going to get a plastic basin, and use glue and cable ties to secure a load of LED rope lights to the inside, then (optionally) rewire them to a central power supply. You make it wearable by cable tying a skateboard helmet to the inside of the translucent basin.

Step 2: LED Rope Necklaces

These are the LED rope light necklaces. They are the kind that street vendors sell to kids at bonfire parties or street festivals (mardi gras?) for a couple of quid (3-5 USD). I guess there are many kinds, but the kind I found run of 3 x 1.5V button batteries, and are controlled by an electronic push button on/off switch.

you can buy them here in the uk

here in the US
multicolor tube necklace

Step 3: Mount the LED Ropes to the Basin

I got a translucent (this is important, so light glows through it) basin from a pound shop (dollar store). it was about 50cm diameter, which is an ok size. for 18 tentacles.

I used hot glue to mount the battery end of the lights to the inside of the basin.
Use sandpaper to rough the surfaces first, then clean them thoroughly so it sticks better. people WILL pull your tentacles.

Leaving 5cm of plastic tube inside the basin. This will let you use a cable tie around this soft bit of the rope and leave everything nice and secure.

Step 4: Tentacles in Place

wow, ok done.

I also put 3 LED rope lights in the top of the basin to light the bell of the jellyfish. If I did it again, I would do more lights in the basin, as it really adds to the effect.

I used even more hot glue to fill all the gaps between the LED rope lights and the basin, before tightening up the cable ties. I'm glad I did this because a bunch of girls in a dance tent utterly mauled my tentacles, but it all held together.

Step 5: Wiring It

I now pulled all the batteries out the rope lights, and used a naked solid wire to go through all the negative terminals of the lights. I soldered it to each terminal, then hot-glued it in place so it wouldn't go anywhere. I then repeated the process for the positive terminal. Remember to glue it all in place so it won't go anywhere - if the 2 wires touch, it shorts everything out.

bascally, you are wiring all the rope lights together in paralell.

Step 6: Control Box and Power Supply

this bit is optional. I used a switch with three positions : locks-on / neutral-off / temporary-on

you don't need this and wiring a simple on-off switch is fine.

I then hooked it all up to a 3 D-cell battery pack. I knew this was overkill, in terms of how much charge I'd need, but i was at a festival for a whole 4 days and didn't want to take any chances. you could probably get away for 3xC-cells or even 3xAA cells for a long night.


you put the 3 cells in series, to make 1.5V x 3 = 4.5V

then you put all the rope lights in parallel.

Step 7: Mounting It

you get any comfortable helmet with holes in the top, then drill corresponding position holes in the basin , and use hot glue and cable ties to mount it on.

I then glued the control box to the back of the helmet, and ran ries down the battery pack on my belt. This is because I was worried about ahving too much weight on my head.

If you were using C or AA cells though, I think you could mount them on the helmet too, and probably not sustain lasting neck damage.

Step 8: Done

there you go, done! mount up and go and freak some people out!

I hope you liked this instructable, please feel free to ask questions or suggest modifications.



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    69 Discussions


    9 years ago on Introduction

    I made this for my 6 year old son for Halloween - was a huge hit. People stopped us and took pictures as we went down the street. Only suggestion was to not put the LED strings in front of his face - I think he was seeing the blinking lights in his sleep for a few days. I think next year I'll make another, so my two sons can be a "swarm".

    1 reply

    11 years ago on Step 1

    excuse me I am new to this Instructables thing and I have a budget. might I ask how much this will all cost? I thank you a lot for this project, I like LED things.

    2 replies

    I LOVE this jellyfish hat!!! Planning on making one this year to wear to Bear Creek Music Fest in November....I am also on a budget & the LED strands seem to be quite pricey...have you had any luck finding a good deal/alternative?

    I built this for less than $50, the link that he used for the US is the best deal I have found. I ordered about 25, assuming some would be broken. I couldn't find a basin so I made a dome of Knex building pieces and covered it in a trash bag. Good luck!


    8 years ago on Introduction

    Hi I love this idea and perfect for a marine theme for a festival coming up. Do you know the best place to buy the light ropes? I found Alter e glow best price but not sure if they are long enough. Thanks! :)


    8 years ago on Step 5

    For wiring the positive terminal, do you solder to the spring?

    1 reply

    10 years ago on Step 8

    I'm in a deep-water aerobics class. Would this work in a pool?

    1 reply

    9 years ago on Step 5

    This is awesome. I will be adding these LED lights to my son's rocket ship costume. If I wire as instructed...will all the LED strands flash at the same time and in the same pattern or will they be flashing out of sync with each other, as they would if I just turned them all on independently? Thanks for your post. Excellent!

    1 reply

    Reply 9 years ago on Step 5

    when you switch them all on together, they start all in sync for a few seconds, then get slowly out of sync due to variations in each strand...! if you were a stickler for wanting them to "wave" in sync you could build a timing circuit that turned the power on and off about once a second.... either way it looks cool....! enjoy


    9 years ago on Introduction

    This is so awesome!!! If I am going to halloween party this is my costume :)


    10 years ago on Introduction

    I have been browsing this site for months and this is probably the most awesome -ible I've come across. Sooooooo creative, fun, amusing, and cute! Thank you.. I now have something to wear on my 21st birthday. :)


    10 years ago on Introduction

    Hi, Just wanted to send you some pix of my jellyfish costume from this past H'ween that was inspired by yours -- I simplified it by using glow-necklaces duct-taped to a salad bowl 'cause the word "solder" is not in my vocabulary :) The pix are kinda crap 'cause every other one was taken with the flash on, rendering me just some dork with a bowl on her head. Looked GREAT in the dark, though! Thank you SO much for the inspiration; everyone dug it! Cheers! Joanie

    1 reply

    Reply 10 years ago on Introduction

    thanks! pics with flash do look really stupid, I shold have warned people about that in the text! ant


    10 years ago on Introduction

    This costume was the most fun I've had at Halloween, the people loved it here in DC. I'll put up some pics when I get em. Thanks again deadinsect!


    10 years ago on Introduction

    I made this for Halloween this year. Everyone loved it, thanks for the idea!

    I got a $6 hard hat from Home Depot, removed the innards, and hot glued some sponges to the inside (otherwise the hard hat sat too high).
    Also didn't bother with the zip ties, just hot glued the heck out of it, which worked fine. In fact, I burnt out a couple during wiring and couldn't remove them! Ended up just cutting the bad tentacles off and gluing on more next to them.

    Best costume idea ever, thanks so much! What are you planning next??