Ballin led tutu plan needs some help

onesillyanna said:

.... I'll get 12 instead of just 8.
I figure if I have one extra set and I have to stop and swap I'll be alright. .....

Click to expand...

Only remember that, if you use two battery holders in serie (8 cells), the set is all the 8 cells ..... i mean, if you want to have a spare set, you need 8 cells in the holders, and other 8 cells as spare set, and change all them together.

Also, mark the different sets so you can be sure to not confuse them, and always recharge all the batteries, before use them ..... as example, if you confuse the sets and use a partially charged cell with other fully charged cells, once the partially charged one go undervoltage and become disconnected, all stop to work (this with "protected" cells ..... with "unprotected" cells, the discharged one can go in reverse charge and overheat or explode)

EDIT: if the white fabric is fluorescent, the effect can be greater, too.

Well, because I tried to get friends to help me at first
(one of them had gone through industrial maintenance classes and was all certified, he is the one who ruined a good portion of my leds like a stupid jerk)
I only have 32 sets of 4 that are in good enough shape to work with.


I figured I'd set them up as two separate series. Half and half. And wire them staggered. It will be extra work but it will make it to where every other strip can be lit if I only have one back up set of batteries and I have to use them.

So I can't get those batteries in my town or the next big town over.
I also am having MAJOR issues trying to order them online.

Is there any alternative battery that will work for 16 sets of 4 leds? That's how I'm wanting to set it up so that the whole thing never has to be completely unlit.

Well, for 4 leds strings, you can try to use 8 alkaline cells (2 of those hosts in serie) ..... it may become a bit low light when they get discharged, but probably still enough light (they are at the voltage limit) .....

Do you have the leds and at least a pair of alkaline AA batteries ? ..... if yes, you can do a test for see how much they can last and how they become dim with discharge.

Connect temporarily 16 leds, with their own resistors, in parallel (i mean, each led with his own resistor connected in serie to the led, then all the series connected in parallel, respecting the polarity), and hook them to 2 batteries in serie ..... this will give approximatively the same current request of all your setup (but for 2 cells only, no reasons to waste 8 batteries just for a test), so you can see if they lit enough, and how much the batteries lasts, and how the leds become dim with the discharge of the batteries.

Would something other than AA's work better?

And would, for the test, two batteries in the battery holder even work or does it need 4 to operate correctly?

C or D batteries have the same voltage, but with more juice.

Another thing you can try to rig up is a Joule Thief (demo) (single 1.5V battery lighting 25 LEDs). It'll let you use lower voltage batteries to power the LEDs and use all the juice in them to power your LEDs until they are completely dead.

That brought up a lot of neat info but I am not knowledgeable in this area to take on that sort of task.
It looks very complicated and I don't think that I have access to those supplies.
Unless you know enough about it to get straight to a plan.
I have two weeks left til go time and that doesn't leave me with disposable hours to sift through tons of info.

Well then it's to late to order batteries from Dealextreme or other such chinese websites.
Do as HIMNL9 suggested and uses strips of 4 LEDS powered by 8 AA batteries with
two of those 4x battery holders wired in series.

Ordering online is really easy, though.
All you need is a credit card or a a PayPal account....:thinking:

The battery holder might not work with only 2 batteries inside, that's my guess.....
But you can do the test with four AA batteries in the holder and two LEDs in series, too.

Yeah I have paypal and know how to use it but the websites were refusing it. I think my bank maybe screwed with my debit card. It expires next month and they may have canceled this one early like some punks.

I'm working on running a test set. I'm getting it rigged now and I plan to keep it at the same ratio even if I have to make a crummy 2 AA battery holder. I like the idea of testing the ratio on a smaller scale.

I just constructed the "super" Joule Thief using the values shown in the video (100pF capacitor, 100kohm resistor) from some parts around the house and a ferrite core (the ring shaped thing in the video) I pulled out of some old electronics. I just wound some random number (maybe 15 or so) of turns around the ferrite. It was able to power at least 7 UV diodes I had on hand in parallel from one 1.5V battery. I didn't tune it and I used some cheap wire from an ethernet cable, but it still worked.

You can probably get similar or better results as well, and adding turns to the ferrite usually improves the brightness. I'll see if I can come up with a parts list from Mouser.com (an online electronics part store) if you want to build it. The total cost would probably be about $5 (~$2 for the ferrite, $0.30-$0.70 for each transistor, $0.60 for the cap and resistor, $1 for a battery holder), though maybe more from the cost of the protoboard to solder the parts from. We can draw what the parts look like and how they'd be connected if you can't read schematics.

Regardless of whether you want to build a JT or not, you'll probably want to buy a real battery holder from an electronics part shop. Better than fussing around with a makeshift holder, especially if you need to swap batteries.

On another note, I compared the brightness of those UV LEDs to a white LED. The UV LEDs looked so dim, so I thought maybe they weren't getting enough current. Well, the white LED is just as bright as ever, so it's really the UV LEDs that are very dim. I don't know how much mileage you'll get from them even at full power as a blacklight source.

I still suggest you consider buying a 6-inch 4W compact fluorescent black lamp rather than go with LEDs. You can strap it to your back and have it flood light outwards. The fluorescent lights put out about 0.5W worth of UV from the fluorescent black lamp; compare that with maybe 5mW per LED--if that--and you'd need a hundred LEDs to even approach the brightness of a single portable lamp. They're only $7 each (alternative). You can still use (and should) regular LEDs (like blue or white) to decorate the tutu, but if you're really looking to "glow" you really need something like the fluorescent light.

Ok, 2 batteries in a battery holder can't work, you need all 4 batteries for close the circuit.

Yes, you can use 4 of them, and 16 x 2 leds in parallel (each 2 leds with its own resistor), for the test.

a joule thief (or better, a self-tuning flyback, like the one they call "super joule thief ) can work with long led strings, but they usually don't give you too much current.

If you can do the test with the 4 batteries, then you get also the estimated duration of a battery set (and, after all, alkaline cells are relatively cheap, so you can carry another 8 extra cells set, or two, for change the first ones when they get discharged, if they last too short time)

Let us know what you decide

Alright, the trouble with buying the 14500 batteries is that my debit card is a mastercard and freaking mastercard won't allow Hong Kong purchases if you're not actually physically there. Due to the frequency of fraud. I don't have any other cards for payment so poo.

Bionic Badger, I do have real battery holders. I have 2 that hold 4 AAs. With on/off switches. Very nice.
The uv will show up fine on all the white tulle. I know it. I did a single led test behind the tulle and it lit up spectacular.

And I really really cannot do fluorescent lamps. I will be at Bonnaroo. Too much dancing and glass is not allowed anywhere on the grounds. Intoxicated people sometimes go barefoot. No bueno.


If you can help me with the joule thief, I'll totally make it but I need simple easy instructions.
What sort of old electronics might have the pieces I need? How many do I need?
And no, I don't know how to read schematics. I'm utterly new to wiring anything.

The joule thieves may be my only option what with how ridiculous it is that I cannot order the 14500's.

I haven't started to solder yet. I'm planning on doing that tomorrow.
That's when I will test out regular AAs. I have probably 60+ regular AAs around the house so it would be alright to go through 16+ of them.

HIMNL9,
Is there a way to do a smaller scale test? 16x2 feels daunting because the few remaining leds that are not prepped for soldering and assembly are in very rough shape and hard to work with while trying not to break them.

You can solder them without cut the leads, also the resistors, for just a test.

Or you can use 4 groups, and then divide by 4 the time (4 groups consumes 1/4 of 16 groups, so 16 groups last 1/4 of 4 ..... if, as example, with 4 groups it last 4 hours, with 16 groups it last 1 hour, and dim 4 times faster when start to dim)

I must have some pretty terrible UV LEDs. Then again, they were from DealExtreme...

Here's a price list for parts for the SJT. I've priced these out in quantities of 10-100 because you get price breaks for quantities, and you will want some extras in case things go wrong. You can reduce the number you want to buy if you want. The most expensive parts are the ferrites. You'll have to decide how many you want to buy and use if you have multiple strands. All parts are from Mouser.com

- 100k Resistor - 100x @ $0.016 = $1.60

- 100pF Capacitor - 25x @ $0.06 = $1.50

- PNP bipolar small-signal transistor - 100x @ $0.038 = $3.80

- NPN bipolar small-signal transistor - 100x @ $0.019 = $1.90

- 1N4001 Rectifier diode - 10x @ $0.07 = $0.70

The above is about $10.

For the ferrites, you have some choices, and I'm not sure exactly how each will perform. You might even be able to get away with one and power many LEDs at once rather than have multiple SJT circuits.

- 31x8mm Ferrite - 4x @ $1.22 = $4.88

- 34x12.7mm ferrite - 1x @ $2.35 = $2.35

Maybe HIMNL9 can comment on the above (and the other parts). They're both not all that different, but the latter might let you generate higher voltages and therefore longer strands of diodes. You could even get both.

You'll also need some wire to wrap your ferrites with. The best would be enameled motor wire because you can add a lot of turns to the ferrite. In a pinch using plain ol' ethernet wire or hookup wire would work too. I don't think it'll really make a huge difference and I think you'll be able to add quite a few turns regardless.

I also omitted the single AA battery holder (since you don't need more than 1 battery). The one I specced is here:

- AA Battery holder - 1x @ $0.69 = $0.69

Mouser's shipping is usually quite fast, and faster if you choose better shipping methods (which I never do). You'll probably get it within the week.

Only one suggestion, about the ferrites ..... if there is a pc shop near you, you can ask them if they have any broken / burned PC power supply for free ..... they have usually at least one toroidal ferrite core, inside, that can be harvested (and also enameled wire) , and also very old types that have no toroidal cores, usually have ferrite rods