Light up "S-Staff" project, questions about batteries

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Mephs
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Light up "S-Staff" project, questions about batteries

Post by Mephs » Fri Mar 22, 2013 4:06 pm

A co-worker recently guided me to this forum to get some insight on a (hopefully) simple project I was thinking about undertaking in the next few months. I'm from around the Boulder area, and I spin a number of things similar to poi, if you're familiar with that, it's a pair of spheres or rods attached to leashes and you swing them around in neat patterns and stuff, usually they have LEDs or come as a ball wick you can light on fire.

In this case, I'm looking to make a custom glow "buugeng" or "s-staff", much like in this video:

http://www.youtube.com/watch?v=TQbrSi4V5RQ

Mainly the problem is that no major companies in this kind of work make such a prop. I've worked with 5050 LED strips on some simple costumes, at home, and can do some basic soldering, and design the actual prop itself, the questions come in with making the prop rechargeable and keeping the weight/size reasonable. Usually for recharging LED props/clothes I use a 12v lithium ion battery pack, which would be fine here except the ones I typically use add a couple lbs and also tends to be too bulky. So after hours of googling around for a "thin 12v rechargeable lithium ion battery", I'm kind of lost as to the best type of battery to use for this project.

Balance is KEY for these kinds of props, if one end is even slightly heavier than the other it can feel really awkward and make certain patterns/trick timings harder to adjust to. The best thing I can think of is to find a battery that is thin enough to fit dead center of the buugeng grip, ideally the housing for such a battery wouldn't exceed 1" in diameter, but I may be asking for a lot. The LED strips use 12V, and ideally the battery should be able to fuel the LEDs for up to 2 hrs of constant spinning at the brightest/most power consuming settings on the lights. (The LEDs also usually include a controller and remote, so housing this element is important also).

I have the general idea in my head how to accomplish it, just the battery and controller housing may be tricky. Any gurus or people with experience that can offer a suggestion on how to move forward with this would be awesome.
Last edited by Mephs on Mon Mar 25, 2013 8:40 am, edited 1 time in total.

markaren1
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Re: Light up "S-Staff" project, questions about batteries

Post by markaren1 » Sun Mar 24, 2013 10:09 am

wow, never seen anything like that before.

Anyway - balance - how about distributed weight, with battery in top, middle and bottom, or 5, or 7 etc.

you will probably need a proper switched power supply to drive the LEDs if you hope for reasonable battery life

what battery life do you want ?

any idea what the light output from these are ?

what is your weight target ?

Also, has anyone done a tear-down of a commercial unit on a web site to see what they use ??

-Mark

Mee_n_Mac
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Re: Light up "S-Staff" project, questions about batteries

Post by Mee_n_Mac » Sun Mar 24, 2013 11:14 am

Can you provide a link to the LED strip(s) you'd like to use ? Are these always just a single color or do you want/need color changing capability ? Is the buugeng always the S shape of must it be able to fold into a C shape ? Is the buugeng "flat" (in section) as the ones carved from a sheet of plywood would be or round like a bent tube would be ? What size is the grip (length by diameter or length by width by height) ?

To me it's an interesting take on the LED hula hoops (as far as the electronics go) you can find. The fatter hoops have used an Arduino Mini and cylindrical batteries and a DC/DC converter to drive their LEDs. Power would seem to be the sticky factor here and I question the need for using 12V. If these strips are using dropping resistors then perhaps most of the power is not going to illumination. Changing the LEDs may then allow better usage of the power and smaller, lighter batteries.

Mephs
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Re: Light up "S-Staff" project, questions about batteries

Post by Mephs » Mon Mar 25, 2013 8:56 am

markaren1 wrote:Anyway - balance - how about distributed weight, with battery in top, middle and bottom, or 5, or 7 etc.
Putting weight on the ends, balanced or not might throw off the feel of spinning it, though this is an option for a prototype design.
what battery life do you want ?
The standard in the industry right now seems to be anywhere from 3-8hrs of continuous spinning on one fully charged battery, so in all honesty that's a reasonable amount of time. This is also assuming rechargeable battery.
what is your weight target ?
As light as possible, buugeng are very light to work with and you grip/spin them very lightly as well.
Also, has anyone done a tear-down of a commercial unit on a web site to see what they use ??
The problem is that no one really produces a glow version of this prop, otherwise that would be a good way to go (but then again if I could buy a quality LED set I would just do that instead of try to build one :)
Can you provide a link to the LED strip(s) you'd like to use ?
http://www.parts-express.com/pe/showdet ... mpaign=pla

This is the type of LED strip I used for a recent project on a vest (not that exact strip but you get the idea) -- I believe the LEDs are called "5050" and I suppose I wouldn't have to use a premade strip like in the link above, I just would need to do some research on how to link up LEDs like those and how to properly supply them with power.
To me it's an interesting take on the LED hula hoops (as far as the electronics go) you can find. The fatter hoops have used an Arduino Mini and cylindrical batteries and a DC/DC converter to drive their LEDs. Power would seem to be the sticky factor here and I question the need for using 12V. If these strips are using dropping resistors then perhaps most of the power is not going to illumination. Changing the LEDs may then allow better usage of the power and smaller, lighter batteries.
I'm pretty new to this electrical tinkering stuff, but I've gotten a couple projects to work. The challenge for me here is really supplying power. 11.6 or 12V Lithium Ion batteries (rechargeable) seem to be the most commonly used for these types of applications. I could of course opt for different types of LEDs, I'm not knowledgeable enough at this stuff yet to really make a marketable product, I just kind of want to custom build a prop that lights up. After some more time to sketch up designs, it's really looking like any power source would HAVE to be housed in the grip, to keep weight centered and to keep the ends light and balanced, I think.

As far as parts go, these are just (general) examples:

5050 LEDS:
http://www.focalprice.com/ERDD3W/T51_50 ... VBxfBzIW70

Battery pack? -- I'm assuming I'd have to solder the pack as pictured to some kind of DC plug widget or piece to charge it? (excuse any terminology failure):
http://sell.bizrice.com/selling-leads/1 ... -pack.html

The battery would sit in the grip with some kind of exposed DC charge input to fill up the battery, with the leds running along the length of the prop, properly wired together. And I think that should really be all I need. Would be nice to add one of those fancy RGB controllers that lets you use a remote control to change the light strobe, colors, speed, etc... but for now I'm quite content building just a single color prop that has a bold glow to start, and then maybe expanding on the design shortly after. Really the big question that slowly starting to make more and more sense is that battery. As far as I know the LEDs require 12v (the led strips I made my vest with needed a 12v pack). I'm not to sure about the other details but maybe those links will clarify some of the needs.

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Re: Light up "S-Staff" project, questions about batteries

Post by Mee_n_Mac » Mon Mar 25, 2013 12:48 pm

Just some info for you re: the LED strips. Generally these are made of multiple "sections" of LEDs (3 LEDs/section for the strip you've used) and the sections are wired in parallel while within each section the LEDs are wired in series. What that means is that you can snip off any number of sections and the remaining LEDs will work OK. Now within the section the "LED" might just be a single LED with a single color or a triplet of LEDs; 1 red, 1 green and 1 blue. So an RGB strip will have 9 LEDs in a section with 3 red LEDs in series, 3 green in series and 3 blue in series in that group. Red LEDs require about 2-2.4 V to work properly so 3 in series need between 6 and 7.2V. If you connected them directly to 12V they'd draw so much current that they'd burn out very quickly. So a resistor is put in series with the LEDs and it limits the current, generally to 20 mA when 12V is applied. Green and blue LEDs run at a higher voltage and to get the same 20 mA they use a different resistor in series with them. The upshot of all this is that perhaps 25-30% of your battery power is going towards heating up the resistors and not toward producing light.

If you use just a single color (R or G or B) and no dimming, each group of 3 LEDs will suck 20 mA of current from your 12V source. If you combine any 2 colors, the current draw will double and obviously triple if you use the R and G and B. Of course the buugeng will be brighter with 2 or 3 LEDs on (per group) vs one so if you want to maintain the same light level you'll need some method of dimming.

My point in this is that you need to consider pretty carefully how many LEDs (how many sections) you really need as that will affect battery life pretty directly. You will probably want some way to dim the LEDs as that can save battery life too. Using LEDs w/o the current limiting resistors means using a proper driver and you can knock down that 25-30% wasted to perhaps 10-15% wasted (by the driver) that way. Helpful but not Earth shaking. Getting hours of life in a small package means a careful tradeoff of max brightness vs battery size vs runtime. Given you have some of the strips you want to use, you may want to experiment with them in a prototype buugeng to see how many LEDs you need to get the desired brightness. When you know that, it'll be pretty easy to figure what can (realistically) be done for battery and runtime and how to package it into the grip. Until then it's just a lot of guessing.

Typical schematic of LED strip, courtesy of AdaFruit
Image

Mephs
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Re: Light up "S-Staff" project, questions about batteries

Post by Mephs » Mon Mar 25, 2013 2:26 pm

This actually gives me some direction. Thanks a ton! Looks like I got some more research to do :)

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Re: Light up "S-Staff" project, questions about batteries

Post by Mee_n_Mac » Mon Mar 25, 2013 4:53 pm

Just one more thought to throw out there ...

Have you seen the LED lit acrylic signs and artworks ? They use a few LEDs that "shoot" light into the acrylic. It bounces around and doesn't "get out" (for us to see) unless there's a scratch that disturbs the light from bouncing off that (now imperfect) surface. I don't know if this would be applicable to your project. It might, or might not, allow you to place a few LEDs in the grip, aimed outwards towards the tips and get the illumination you want.

Just an idea to stir the creative juices ...

Image

Image

Image

macegr
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Re: Light up "S-Staff" project, questions about batteries

Post by macegr » Mon Mar 25, 2013 7:49 pm

You may want to consider EL wire. Four or five strands of high-brightness EL wire bundled together and would be lightweight. They are also pretty efficient and produce a single line of light source instead of many small dots.

Mephs
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Re: Light up "S-Staff" project, questions about batteries

Post by Mephs » Tue Mar 26, 2013 9:59 am

I had some time to sit down and do some more looking around, I'm wondering if I could piece this together easily using the following:

LEDs, premade strip:
http://www.amazon.com/Non-Waterproof-50 ... B006LW2NJM

Battery housing:
http://www.creativelightings.com/8-AA-C ... FQ&click=2

And just use NiMH rechargeables (2500 mAh?) -- if I can get away with 4 AA batteries and get 3+ hrs of life out of it though that'd be ideal...but I think I'm going to need 8 to get a reasonable amount of spinning time out of the prop. I'd power the strips with those and make the handle also the house for the batteries. LED strips would run up and down each side of the curve (so top and bottom, back and front, 8 strips total, with the wires running around in a single direction as well.

I need to do a prototype with rechargeable AAs and see if they'll work for this application but I think they should, all of the LED strips are standardized to work with just a 12V power supply, and this way the batteries are charged seperate from the prop.

Does any of this sound wrong off the top of anyone's head? I've actually seen examples of EL wire used for custom props and they seem kind of "dull", but maybe that's just some cheap low quality EL wire being used. EL wire is definitely an option otherwise.

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Re: Light up "S-Staff" project, questions about batteries

Post by Mee_n_Mac » Tue Mar 26, 2013 10:43 am

4 rechargable AAs might get you about 5V, not enough to run the strip w/o a DC/DC voltage converter. How many LEDs are there on the 5m of the strip ? You can begin to get a handle on the run time by knowing how many of the previously mentioned "sections" there are to be powered. Each "section" would draw 20 mA for any singe color (R, G or B) on. Perhaps a good guess is to say that with dimming and some color mixing, each "section" would draw perhaps 30 mA ? I'm fairly sure each RGB triplet of LEDs is counted as a single RGB LED by the vendor and so each "section" is counted as 3 LEDs which gives us 10 mA per RGB LED.

So if a 5m strip has 300 LEDs, it'll use 300 x 10 mA = 3000 mA = 3A at 12V. If you had a 12V battery rated at 2500 maH, you might expect about a 2500/3000 = 0.83 hr = 50 min runtime. If you have to use a DC/DC converter you need to do another step. The power out to the strip is equal to the power in to the converter plus add perhaps a 15% penalty. Power is voltage x current so the easy way to think of this is the compare the input and output voltages. If you have 12V out and 5V in (from the 4 AAs) then the input current must be 12/5 times larger than the output current. And then add another 15% due to inefficiency of the DC/DC converter.

So if your 5m strip uses 3A @ 12V then the battery @ 5V must supply (3A x 12/5) = 7.2A. Now add the 15% so 1.15 x 7.2A = 8.3A. Assuming the 4 AAs could even supply that amount of current (very dubious IMO) then you'd get 2500/8300 = 0.3 hr = 18 min of runtime. Gack ! Just using a single color would reduce the current draw to 66% of the above and increase the lifetime to 18 min / 0.66 = 27 mins. Dimming the LEDs by 50% (or halving the number of LEDs used) would double the run time to get about 1 hour. It also reduces the current draw out of the batteries down to ~2.75 amps, a somewhat almost reasonable number. I would have to say what's needed is probably a LiPo instead of NiMh's.

Mephs
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Re: Light up "S-Staff" project, questions about batteries

Post by Mephs » Tue Mar 26, 2013 12:16 pm

Mee_n_Mac wrote:4 rechargable AAs might get you about 5V, not enough to run the strip w/o a DC/DC voltage converter. How many LEDs are there on the 5m of the strip ? You can begin to get a handle on the run time by knowing how many of the previously mentioned "sections" there are to be powered. Each "section" would draw 20 mA for any singe color (R, G or B) on. Perhaps a good guess is to say that with dimming and some color mixing, each "section" would draw perhaps 30 mA ? I'm fairly sure each RGB triplet of LEDs is counted as a single RGB LED by the vendor and so each "section" is counted as 3 LEDs which gives us 10 mA per RGB LED.

So if a 5m strip has 300 LEDs, it'll use 300 x 10 mA = 3000 mA = 3A at 12V. If you had a 12V battery rated at 2500 maH, you might expect about a 2500/3000 = 0.83 hr = 50 min runtime. If you have to use a DC/DC converter you need to do another step. The power out to the strip is equal to the power in to the converter plus add perhaps a 15% penalty. Power is voltage x current so the easy way to think of this is the compare the input and output voltages. If you have 12V out and 5V in (from the 4 AAs) then the input current must be 12/5 times larger than the output current. And then add another 15% due to inefficiency of the DC/DC converter.

So if your 5m strip uses 3A @ 12V then the battery @ 5V must supply (3A x 12/5) = 7.2A. Now add the 15% so 1.15 x 7.2A = 8.3A. Assuming the 4 AAs could even supply that amount of current (very dubious IMO) then you'd get 2500/8300 = 0.3 hr = 18 min of runtime. Gack ! Just using a single color would reduce the current draw to 66% of the above and increase the lifetime to 18 min / 0.66 = 27 mins. Dimming the LEDs by 50% (or halving the number of LEDs used) would double the run time to get about 1 hour. It also reduces the current draw out of the batteries down to ~2.75 amps, a somewhat almost reasonable number. I would have to say what's needed is probably a LiPo instead of NiMh's.
http://www.excellent-led-lights.com/smd ... -p-10.html

This strip carries 600 LEDs per 5M, but I'm thinking the length of a buugeng is between 31-34" from end to end, so consider 34"x4 = 136" = 11 ft (11 ft / 16 ft) -- so roughtly 400 LEDs. Probably a bit under that estimate since curvature and whatnot. I think if I mount the LEDs on a thin reflective surface frame it could greatly amplify how it looks, too but I'd need to play around with that theory.

So if I'm understanding correctly, something like this http://www.dhgate.com/bty-3000mah-ni-mh ... b65b4.html I'd need 10 of those to get 12V? And 400 LEDs would roughly eat 2666 mA per hour? -- So all in that, brightest output I could hope for 1 hr of spin time before I'd run outta juice?

Just seeing if I'm following you correctly.

There is this...the dimensions are kinda unclear and may be too much lengthwise. But 12V and 5400mAH rechargeable.

http://www.tomsi-battery.com/products_i ... 93525.html

Given that 400 LEDs would be an extreme case, I might be able to cut down to 200 LEDs if my theory on using a very reflective frame to nest the lights on works out, then I wouldn't need as many.

Assuming 5400mAH in this case then with 200 LEDs (x10 mA) = ~almost 3h. 6h if I were to manage to cut it down to 100LEDs (using wider spaced RGB led strip instead).

Whew. This is confusing stuff, but I think I'm getting some kind of grasp on it. :dance:

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Re: Light up "S-Staff" project, questions about batteries

Post by Mee_n_Mac » Tue Mar 26, 2013 3:03 pm

Mephs wrote:Just seeing if I'm following you correctly.
So far so good !
Mephs wrote:There is this...the dimensions are kinda unclear and may be too much lengthwise. But 12V and 5400mAH rechargeable.
http://www.tomsi-battery.com/products_i ... 93525.html
Given that 400 LEDs would be an extreme case, I might be able to cut down to 200 LEDs if my theory on using a very reflective frame to nest the lights on works out, then I wouldn't need as many.
Assuming 5400mAH in this case then with 200 LEDs (x10 mA) = ~almost 3h. 6h if I were to manage to cut it down to 100LEDs (using wider spaced RGB led strip instead).
Whew. This is confusing stuff, but I think I'm getting some kind of grasp on it. :dance:
I've got good news and bad news re: the above calculations. The good news is that the LED strip you linked to above had 600 LEDs and used 48W @ 12V. That works out to be 6.66 mA/LED. So 400 LEDs draws the 2666 mA that you mentioned above. And 200 obviously half that, 1333 mA. So IF the battery were to live up to it's claims, that would be about 4 hrs. And 8 hrs for 100 LEDs. Dancing now ? :mrgreen: Notice the IF.

So that was the good news. Here's the cautionary news ... that battery pack is comprised of 6 type 18650 cells. Given the current rating and voltage stated for the pack, I can tell you that it's set up as 2 sets of 3 cells. Each set has 3 cells in series giving you a nominal 11.1 V and 2500+ mA. The 2 sets are then in parallel giving you 11.1V (not 12V) and 5000+ mA. So the stated current spec may be reasonable but the voltage spec is a bit over stated. The chemistry used in that battery is Li-Ion and so it's voltage varies a bit from fully charged to "empty". Li-ion cells, like the Li-Po cells, need to be treated carefully. You don't want to leave them sitting around fully charged for a while (it's bad for the battery) nor do you want to leave them sitting around "empty" (same reason). You also have to be very careful not to really really really empty the battery, or to overcharge it, or to draw current in excess of it's stated capacity ... they will and have blown up and caught fire (remember the Sony laptop fires of some years ago). Some of the 18650 batteries also incorporate self-protection circuitry so those bad things are less likely. Ask the vendor if the pack you're buying uses "protected" cells.

And now the (maybe) bad news ... any Lithium based cell has a variable output voltage vs state of charge. Li-Ion's start about 4.1-4.2 V when fully charged and when they get down to ~3.0V there are considered "empty" (safely) and should not be discharged any more (you may permanently damage them). So the voltage from 3 cells in series will vary from (3x4.2) = 12.6V (yea !) to (3x3.0) = 9.0V (ugh !). Your LED strip will run over a range of voltages but at some (lower than 12V) voltage it'll stop getting dimmer and just shut off. The shut-off voltage will depend on the color of the LEDs and how the strip is arranged. I will opine it will be above the 9.0V mentioned above, and GUESS that around 10.5 to 11V the LEDs will be too dim to use. That's around 3.5 - 3.7V per cell. So what's this all mean ? Well even though the battery may be able to supply the current needed to run all the LEDs, at some point the voltage will drop enough below 12V that they won't work and so you won't get the expected lifetime, as calculated from the number of LEDs and current draw, etc, etc. You can look at some Li-Ion discharge curves (below) and figure how many hours vs current draw and voltage you might expect from a typical Li-ion battery. Know that identical batteries in series maintain the same current as a single battery, it's the overall voltage that goes up. Batteries in parallel keep the same voltage but the current capacity goes up. Ideally with the 6 cell (3S2P) the current draw of the LEDs is split evenly so if you have 400 LEDs drawing 2666 mA, that would be 1333 mA from one set of 3 cells and 1333 mA from the other set of 3. Look at the 1A (=1000mA) curves below to see the voltage vs runtime for the cells tested. When the voltage gets below 3.5 - 3.7V that's your shut off point. My take is that the average Li-Ion cell tested had perhaps 6 W-hr of capacity at that 1000 mA discharge rate. Using the nominal 3.7V, that 6 W-hr translates into (6/3.7) = 1.62A-hr or 1620 mA-hr of capacity. And at the 1000 mA rate that would be 1.6 hrs before the battery falls below a useful-to-you voltage. Your rate is a bit higher so the runtime might be a bit less. Compare that to the 2 hrs calculated (for 400 LEDs, 2666 mA) when the voltage was assumed to be 12V and not changing.

http://lygte-info.dk/info/Batteries18650-2011%20UK.html

TMI ?? :mrgreen:

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Re: Light up "S-Staff" project, questions about batteries

Post by Mee_n_Mac » Tue Mar 26, 2013 3:22 pm

Actually that same site had newer tests and an easier way to understand the results. Look at the discharge time v voltage curve for the 1000 mA rate (it's the closest to to your 400 LED case). You can see the average battery gets to the 3.6V shut-off-for-your-LED-strip at about 1.3 or so hours. Compare that to the 2 hours "simple" estimate.
Image

If you cut the LEDs down to 200 that's a 1333 mA draw or (ideally) 666 mA from each cell in the pack. Use to 500 mA curves. You get 3.25 (?) hours of runtime before the voltage gets to 3.6V or below. Compare that to the 4 hour simple estimate.
Image

http://lygte-info.dk/review/batteries20 ... %20UK.html

Is the (?any ?) battery pack built from better cells than those used in the test ? Worse cells ? I suspect the cells are mostly all the same but who knows what comes out of China these days.

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Re: Light up "S-Staff" project, questions about batteries

Post by DennisCuevas » Sun Aug 18, 2013 1:01 pm

Mee_n_Mac wrote:Can you provide a link to the led light strip(s) you'd like to use ? Are these always just a single color or do you want/need color changing capability ? Is the buugeng always the S shape of must it be able to fold into a C shape ? Is the buugeng "flat" (in section) as the ones carved from a sheet of plywood would be or round like a bent tube would be ? What size is the grip (length by diameter or length by width by height) ?

To me it's an interesting take on the LED hula hoops (as far as the electronics go) you can find. The fatter hoops have used an Arduino Mini and cylindrical batteries and a DC/DC converter to drive their LEDs. Power would seem to be the sticky factor here and I question the need for using 12V. If these strips are using dropping resistors then perhaps most of the power is not going to illumination. Changing the LEDs may then allow better usage of the power and smaller, lighter batteries.
Hei I also need that. I've very much interest in led's and wanna learn a lot. Thanks all of you... :drool:

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Re: Light up "S-Staff" project, questions about batteries

Post by Mee_n_Mac » Sun Aug 18, 2013 8:24 pm


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