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.

wiring

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.