Introduction: 21 LED Rechargeable Hula Hoop

Picture of 21 LED Rechargeable Hula Hoop

DIY 21 LED Hula Hoop
Updated : FEB 28, See my website for more pictures and wiring diagrams.
21 led's inside a 3/4 inch pipe for faster hooping styles.
I previously made a instructable how to make a 42 LED hula hoop. But my most popular hoop on my site is the 21 LED so i decided to make another instructable for this one. It is very similar with a little different wiring.

Background:
I started learning about this because my GF wanted a LED hula hoop for christmas. After seeing sites online selling them for $250+ for rechargeable ones.. I decided i could make it myself for half that and rechargeable.

Takes about 3 hours to make

Step 1: Supplies

Picture of Supplies

Here is a list of supplies you will need. All my prices are in Canadian funds. You can get things a little cheaper from ebay and such. But this was all bought from local
plumbing and electronics stores.

The hardest thing to find is a good tubing product. I wanted to use something that was fairly cheap, came in short lengths and had the proper strength and transparency i needed. The product i found that works best is Aqua-pex. It has writing on it with the brand and specs.. but it won't be noticeable at night , when you will be using a LED hula hoop anyway.

Supplies List
21 LEDS - $12.00 on ebay
132" of 3/4" pipe - $20.00 for 20 ft. Aquapex also available on ebay
1 x 3/4" pex coupler - $1.00 home depot or ebay
2 x 3/4" pex clamps - $0.50 home depot or ebay
36' x 22 ga Wire - $15.00 for 100 ft.
4 x AA NIMH rechargeable batteries - $18.00
1 x 6 volt battery charger - $15.00
1 x 1.75 x 4.75mm plug and dc Jack - $4.50
21 resistors - $2.00 for 100
1 x Slide Switch SPST on-off $$9.00 for 10
Everything comes to around $70
Plus a few basic tools you may already have.
Tools List
Soldering Iron, Drill, Solder, file or sandpaper, Flux, Electrical tape, marker, glue, pipe cutter, String, Wire strippers, Bubble wrap, and a paper clip.
http://farm4.static.flickr.com/3086/3184154764_7029162aae_t.jpg

Step 2: LED and Resistor Information

Picture of LED and Resistor Information

Resistors are basically used to drop the voltage so you don't fry the LED or draw more power then it needs.
Each LED requires a different voltage to light up. Some 2.4volts, some 3.6volts and so on.
Using OHM's Law, i calculated that with 4.8 Volts (4 x AA Rechargeable's). I needed 68 ohm resistors for the 3.6 V led's and 150 ohm resistors for the 2.4 and under
LED's.
Some people use exactly 3.6 volts, lithium or 3 AA batteries. But as soon as the batteries start dieing, they lose voltage and some LED's won't light up as bright or at all.

Use this tool to calculate which resistors you need for your LED's LED Resistor CalculatorLED Resistor Calculator
Soldering the resistor is very easy. You can put the resistor on either the negative or the positive. It doesn't matter. I used the positive. Usually on a LED, the positive is
the longer of the 2 leads. I cut my positive leads before soldering, to make the length of each almost the same after i solder the resistor.

Step 3: Soldering Batteries

Picture of Soldering Batteries
So I started the process by soldering all my batteries together in series. Basically negative terminal goes to the positive on the next battery. I wanted to evenly distribute
the weight around the hoop so I separated the batteries by 31-36" of wire, so i had some extra to play with. I created a little video to show you how easy soldering a
battery is. . WARNING! Soldering batteries is very dangerous and they could explode. Try at your own risk.
Video
Soldering Batteries.
Prepping the batteries. I have used many different kinds of batteries. This time i am using Venom 2400 mah batteries. I start off by charging them. Then I take my cheap
nail file and scratch up the tops and bottoms. Just so the solder has something to grab onto.
Since my hoop is 132 inches, batteries are 2 inches long and i need 4 of them. I need to have etleast 31 of wire in between each battery. So i made it 32 inches just to be safe.
Strip each end of the wire.
Put some FLUX on the battery end and the end of the wire. It acts as a bonding agent for the solder and makes soldering so much easier.Put a big glob of solder on
the soldering iron. Touch your wire to the battery and push the soldering iron on top. It shouldn't need to be help on there for more than 5 seconds. Remove the iron, and
blow on the solder. It should harden and you will be able to pick the battery up with just the wire. If it falls off try again.

Step 4: Charger Plug

Picture of Charger Plug

I changed the plug for the battery charger to a barrel plug. And used a hold jack for the receiver in the hoop. So the Jack could be more inside the hoop and less exposed. So I soldered the positive wire to the
middle and negative to the outer. It will be the same for the jack hole.

Step 5: LED Wires

Picture of LED Wires

I purchased 1 spool of Red 22 awg wire. So to distinguish the positive from the negative i took a marker and ran it down one length of the Red wire. I also purchased a second spool of white. You can use it for the second strand of LED's in the 42 LED version or use it for the batteries or what have you. I have recenlty switched to using white for both, as it is less visible through the hoop. And using only a piece of red at the end of the batteies line so i know when i pull the lines through the hoop which is the battery positive.
Next run the wires for the LEDS, Positive and ground. Mark out where you want the LED's and the batteries to go.
For 21 LED's per length of 132" wire. It was about 6.5 inches in between each led.
Make sure you leave enough room between the LED's for the batteries, no soldering or tape or they wont fit in the pipe.
Solder your resistors to your longer part of the LEDs.
And then solder the resistor to the positive wire.
Solder the other line of the led to the ground.
Tape up your exposed wires. And tape the wires together. Move on to the next led.
Always test the string before you move on to the next step. You can use a 9 volt battery to make it easier. Just touch the positive string to the small port and the negative
to the pole with the folds.
This step take the most time. Took me about 1 1/2 hour to do the 21 L.E.D.'s
Update:
I recently found out that you can attach the battery negative to the LED negatives. See the pic. This way you only need to attach the negative to the DC jack. And you don't have any wires going across the gap in the tubing when you are finished. Its works better this way for the collapsible version.

Step 6: Bubble Wrap Wires

Picture of Bubble Wrap Wires

After you are done soldering, you want to attach all the wires together.The led lines, the battery line and some string.
After all the lines are attached together. You want to bubble wrap between the batteries. To make the hoop quieter. And protect the led's.
Remember you want the batteries to be able to slide through the pipe. So only bubble wrap the led's and wires. leave that batteries exposed. Start at the end that will enter the hoop last. So the overlapping doesnt bind in the hoop when pulled through.
If you want to add some weight for a fitness hoop, just add some fishing lead weights in this step. Or make your hoop last longer using another 4 batteries in series. Double the Capacity.. but that would be a little more planning and different wiring.

Step 7: Charger Jack and Switch Placement

Picture of Charger Jack and Switch Placement

Next I drilled the holes for the switch and the dc jack. You want to place them far enough back that you can still get the coupler all the way in. I used a 1/4" drill bit. 1 hole
for the dc jack, 2 holes for the switch and just ran the drill back and forth till it made one long hole for the switch to fit.
In the pic i used a spare section of pipe just to test the placement.

Step 8: Pull the Wires Through

Picture of Pull the Wires Through

I attached another piece of string to the string tied to the lines, in the bubble wrap. At the end of that string i attached a battery for weight and slid it trough the pipe. I pull my wires through with the closed end of the wiring first.
Now with the wires sticking out the end of the pipe with the holes for the switch and jack. Take the positive LED wire and snake it through the Switch hole.
Take the negative from the LED/battery and pull it through the DC jack hole
I take the positive battery wire and pull it through the opening of the pipe. Then from there i snake 2 lines back one for the dc jack and one for the switch. Here is a diagram. and some pics Hope it makes some sense.

Step 9: Finishing and Connecting the Hoop

Picture of Finishing and Connecting the Hoop

After connecting and soldering all the wires. I put glue/epoxy around the outside of the switch and DC Jack. Then pushed them into the pipe.
Now they should work while the hoop is separated.


Permanent:
Since I didn't want to buy the $200 tool needed for the pex clamps. You can just take your finished hoop to home depot and they will let you use their rental tool for free. Pex clamps hold great, and they are .28 cents each. Or you can use a gear clamp. Taped it up for aesthetics and safety.

Collapsible:
Now i use 3/4 x 8-32 screw posts and some 5/8 Round wood dowling in the middle of the tubing. Works great.

Comments

lhj734017 (author)2013-02-19

2 questions: im under the impression that the charge current needs to be about 150% of the battery's capacity (4.8V*1.5=7.2V). Could you please explain how you determined the 6 volt charging current?
2nd, using this charger, about how long does it take to charge the batteries? (ok maybe 3 lol) and is it a smart charger (changes current applied) or normal (constant voltage applied)?

mrboring (author)2012-09-10

I'm hoping you still check this. I know it's a 6V output, I can't read the amperage. Any more details on what to look for will help.

danny_01 (author)2012-02-16

think this is a great design would it be possible to put a micro controller so the LEDs could have a few chase's on a button ?

mwilson39 (author)2011-11-09

"I attached another piece of string to the string tied to the lines, in the bubble wrap." .... Does that make since? Are the batteries suppose to be attached on there own wire? Negative and postive? Do I attach the led wire and the battery wire together?? What do I do??

mwilson39 (author)2011-11-03

Okay so I am hooking up all my LEDS with the correct resistors and the first one is blue and it worked . I added a few more and now the blues ones do not work, but the yellow and green ones work. Whats going on ? It is getting frustrating :( I just want to finish and hoop it up!

the Hydra (author)2009-08-27

Why do you solder a resistor for every LED? Why not just wire all the LEDs in series and place a large enough resistor at the front of the circuit? Then you'd only have to connect the last LED to ground as well. Seems like it would save a lot of time. Yeah, if one LED went down it would shut down every one after it (like older Christmas lights when one bulb is taken out or blown and the rest of the strand goes dark). LEDs are very versatile and long lasting though, so I don't think you'd have to worry about that too much.

sparr (author)the Hydra2009-09-14

One LED dying turning off the circuit isn't the problem. The issue is when one LED shorts out (the other kind of death). That would increase the current to the rest, so another one would short out sooner, which would increase the current to the rest... Not only does it stop working, but you actually kill all 21 LEDs.

the Hydra (author)sparr2009-09-14

In the rare case that the LED would end up shorting (mechanically breaking inside the LED housing and actually creating a short circuit), you would see the LED that was out. It would take a lot less time to unsolder that LED and re-solder in a new one to take it's place then it would for you to solder a resistor and a ground wire to every LED that you want to use. Plus, even if you have them wired in parallel you still have the chance that an LED will short in the same manner in which case you are going to want to replace that anyways. So I really don't see much justification for wiring them in parallel instead of wiring them in series. Yea, the light at the end technically wont be as bright as the one in the beginning but there is no way you will see that difference with the naked eye.

agr00m (author)the Hydra2011-08-17

Soldering the LEDs in series would require a MUCH greater power source. Essentially in parallel you only need the source to be big enough to power a single LED, in series the voltage required is added, so 20 3.6v LEDs would require a 72v power source.

the Hydra (author)agr00m2011-08-18

you're right. My brain apparently was shut off then lol. It would be nice to find something to just use as a ground rail and a power rail that you could use to wire the resistors and LEDs between instead of running individual wires.Obviously you would need to isolate the two rails from each other. But yea, definitely need them in parallel otherwise the voltage requirement goes through the roof.

agr00m (author)the Hydra2011-08-18

Maybe I've got the wrong idea of what you're saying, but I think that's what he is doing, or if not that's what I do. I take a length of paired 18 awg speaker wire, pull the two apart and use one as my ground rail and the other as the power rail. In his instructable a 3rd is needed to wire all the batteries together. Here are two diagram I made a while ago to help a friend with wiring a hoop. The first is a schematic for a regular, non-rechargeable hoop and the second a hand drawn diagram of the OPs rechargeable setup. The one in the instructable was a bit confusing so I "tried" to clean it up a bit.

Standard diagram
https://picasaweb.google.com/117660769616171838596/LEDHoopTutorial?authkey=Gv1sRgCJ-_lIfkipHyDg#5620483850003965250

Rechargeable diagram
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B_uJZZ1yX4MCNDcxYjFjOTMtMTY1Mi00N2JmLThhYjAtMDc0YTc4OTEzMDYy&hl=en_US
(looking at it now I should have at least used a ruler...hehe)

the Hydra (author)agr00m2011-08-19

Hmm, must have changed since I read it two years ago lol. When I read it two years back it said to run an individual wire to each LED/resistor pair. I'm too lazy to re-read through it, but judging by your response I am guessing that is not the case anymore. Thanks!

agr00m (author)the Hydra2011-08-18

Oh, actually the schematic is for a 2 circuit setup. Two power rails and a common ground rail, each with it's own switch. I think the rechargeable diagram link is bad, the URL is too long to fit in the box...hmmm.

I had to break it up into 3 lines, so just piece it together :)
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B_uJZZ1yX4MCNDcxYjFjOTMtMTY
1Mi00N2JmLThhYjAtMDc0YTc4OTEzMDYy&hl=en_US

eschuhrke (author)2011-06-22

how long does your hoop keep its charge with all leds on?
i have a simular design and i have trouble with time of use.

dhackney (author)2011-03-18

battery negative?

shaymorgan1 (author)2010-04-24

I just bought some of the white pex tubing from home depot to make hulas before I saw this site. Is the tubing you are using clear? Will the led show thru the white pex?? I have included a link to a photo of the pipe I purchased.

http://www.homedepot.com/h_d1/N-5yc1vZ1xiu/R-100139315/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

dog812 (author)shaymorgan12010-04-24

Hey  sorry i havent checked this in a long time everyone..

The pipe is called Aquapex, not available at home depot. Depending where you are located, here in vancouver Andrew Sheret carries 20 ft lengths. Also check ebay. They have 20 ft - 300 ft lengths.

metajessica (author)2009-07-09

What happened to your website? I bought a kit from your website about a month ago, but now it is redirecting to SuperHooper.org with no instructions or kits.. Bummer. I love the hoop I made from the kit. On an unrelated note, I remember seeing somewhere that you can not charge the hoop for more than a certain length of time. I accidentally left it plugged in for approximately 20 hours now and it no longer works. Any advice?

you can find similar kits with instructions at prodmod.com

rooster8d (author)2009-02-15

were can I get one of these Chargers??? Thanks in advance

dog812 (author)rooster8d2009-02-17

Any Radio control shop should sell 4 cell chargers. Or i can sell yah one.. email me through my site.
http://ledhulahoop.com

the_mad_man (author)2009-02-09

my dad just walked out about 1 minute ago, and he said that coloring the wires with a sharpie is a bad practice (he's an electrician). but, my dad is the kind of person who goes on for EVER if you get something wrong.

dog812 (author)the_mad_man2009-02-10

I agree that buying 2 seperate colors is easier to work with.. but this is supposed to be on a budget, and we are talking about AA batteries here , not anything dangerous.

the_mad_man (author)dog8122009-02-10

yeh. suppose so

joejoerowley (author)2009-02-08

Nifty.

dog812 (author)2009-02-08

If anyone has any questions or comments please feel free to email me through my website.
LED Hula Hoop

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