LED Lighting Help

A place to discuss all things involving power and technology (including cameras). Generator tips, alternative energy, lighting your camp/bike/art/self, sound systems and more.
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trilobyte
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LED Lighting Help

Post by trilobyte » Fri Jun 22, 2007 12:43 am

I know, I know. There's an all purpose illumination 'sticky thread' on this board. But sifting through 13 pages of posts and some great responses, it became pretty clear to me that a) the lighting technology available to most artists and run-of-the-mill burners has drastically changed/improved in the last few years.

I do need some help, though. Specific to LED's, and I think it's something that could prove useful for a lot of people.

With this year's theme (the green man) and a general interest in conservation overall, LED and other low power lighting is of great interest to me. LED's seem to break down into a few categories, though. Category one is off the shelf, pre-packaged stuff like kits and LED fixtures. Great, durable, flexible, and low power to say the least. That's low hanging fruit, any of us can take advantage of that just by spending the money on the gear.

The next level is a bit elusive to me. Stuff that requires very little electronics experience (minimal soldering or wiring skills). Has all the benefits as above, but adds in a lowered cost because it's DIY.

Then there's the cheapest level, which is basically buying the raw components and making it yourself.

I'm neither a genius nor a slouch when it comes to electronics. I'm relatively smart, and I want to do some cool (and environmentally responsible) things on the playa with regards to illumination. Where can I get a start? Can you lighting wizards please recommend some resources where those of us interested in putting together low power lighting solutions can get some tips?

Suggested projects for getting basic LED's going? Primers for getting into working with SMD's? Ideas for working with PIC controllers and all that? I don't know enough to be dangerous, just enough to be frightened. I appreciate any help you can give me.

~Trilo~

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Post by StevenGoodman » Fri Jun 22, 2007 9:50 am

LED DIY is pretty easy.

I made a simple LED lightling system for BM2006. Consisting of:

Two 35 Amp-hour deep cycle batteries (in series, for 24V)
One Luxeon 350mA DC LED Driver
(example:
http://www.luxeonstar.com/item.php?id=5 ... 23-D-E-350
Six Luxeon 350mA LEDs in series
(example:http://www.luxeonstar.com/item.php?id=3 ... =LXHL-MW1D

Very simple. The batteries will run the six LEDs for the week of Burning Man, assuming you only run it at night. For BM2006 I banked the six LEDs into one "fixture". At BM2005 the same equipment was used to light the Plastified Forest art project, where each LED lit one "picture".

For BM2007 I will bring them back, but I haven't decided on the configuration yet.
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Re: LED Lighting Help

Post by robotland » Fri Jun 22, 2007 12:07 pm

trilobyte wrote:adds in a lowered cost because it's DIY.

Then there's the cheapest level, which is basically buying the raw components and making it yourself.
Not always true, unless you already own or have access to all necessary tools and piecesparts. Also, time is money- I'm spoiled on those 12V automotive LEDs that come in little packs of 3 or 4, since they already have nice long leads attached. If purchased from a surplus outlet, they're only around a buck-buck fifty per.
Often yard sales or thrift stores will yield ready-to-rock modules for lighting or effects, in the form of toys and appliances, for much less than even the cost of raw materials. And it's a satisfying victory, to reclaim something that nobody else saw the good of. Since few of you are around my stomping grounds to spoil my hunt, I'll mention a favorite FREE find- Those 6V-12V motors in PowerWheelz cars. Free from the curb in satisfying quantities, twice a year in most communities around here and sporting downright badassin' gearboxes just packed with torque.
But then I'm a junk man, and often alter my blueprints to accomodate new finds. Those who actually adhere to the plans (!!!) may find it harder to play this way.
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Post by gyre » Fri Jun 22, 2007 2:14 pm

What exactly are you trying to do?

For lighting, LEDs are only more efficient in lower levels and in cold.
You can make a nice tent kit of one and three watt luxeon LEDs, if that is bright enough.
LEDs run from 1.5 to 7.5 volts dc usually.
If you run a 12 volt LED when you aren't running a 12 volt system already, you are wasting a lot of power.
You can also get converters that shift power to the level you need.
This isn't cost effective for a few LEDs.

Electronic supply houses like Carlton-Bates are the cheapest suppliers, generally.

http://ledmuseum.home.att.net/

http://www.candlepowerforums.com/

http://www.elektrolumens.com/

You have to match the polarity (direction) and voltage to the LED.
This can be as simple as a 1.5 V battery taped to the LED leads, or a regulator controlling the power.
The best are Pulse Wave Modulators like the digital headlamp from Nite-hawk that can be dimmed efficiently.
For a tent kit, you could match the battery to luxeon lamps and have on/off switches.
The battery pack sits on the floor and wires run to the LEDs on the ceiling.
Be sure to use an aluminum heat sink on the back.
It doesn't have to be fancy, but it does need to be joined with silicone dielectric grease.
It can be a chunk of aluminum..

Over a certain level, fluorescents are far more efficient.
A three watt luxeon is good for about 25 lumens/watt.
They are wide angle.

http://www.lumileds.com/

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Post by gyre » Sat Jun 23, 2007 2:40 pm

I should mention that you can adapt LEDs to most voltages with a resistor of the right size.
You usually end up wasting a lot of power that way though.
That's what the automotive LEDs are, an LED with a resistor in series so that the LED sees the voltage it needs, usually 1.5 to 3 volts.

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Post by robotland » Sun Jun 24, 2007 4:37 am

Actually, lots of 'em are just plain twelve-volt LEDs. No resistors.

Another observation about using LEDs- If you have some old mechano-electric or electronic toys around, try popping the cases off and randomly connecting LED leads to spots on the circuit board (if there is one) or along the wiring leads. Often you can get either straight-on lightup effects or pulsing, glowing patterns. Sometimes you also need to clip the speaker leads, though, to avoid endless refrains of "Frer Jacques" or "Old MacDonald". Most thrift stores will have at least one or two usable toys- I recommend looking for toddler ball-shaped toys with big, simple buttons and lights. Easy to hack....I got a great circuit from one of these that enables one of my robotic contraptions to greet me with "Hello, Baby!" when I turn it on...
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Post by reefhugger » Mon Jul 09, 2007 3:41 pm

MAKE magazine has a beginner microcontroller kit and tons and tons of LED projects, big and small, posted online by their users. I'm learning on the 'What is a BASIC stamp microcontroller?' kit from RadioShack. Expensive, but invaluable - especially if you work in science and/or have an interest in data loggers.

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Post by trilobyte » Wed Jul 11, 2007 5:32 pm

Some very interesting responses... and an apology on my part, I neglected to get into any of the specifics of my project.

I'm in the process of building an art car. I'd like to have some small, low power LED's on the vehicle to be able to provide some basic lighting of the vehicle itself. Think like landscape lighting on a house.

The vehicle will have other exterior lighting, both for effect and for safety. But I'd like to be able to light up the ship itself. Without spending a vast fortune, without completely flooding the surrounding playa (and passengers) with light, and without consuming too much power. I do have some basic skills, and the time to do the work myself.

~Trilo~

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Post by Teo del Fuego » Wed Jul 11, 2007 5:45 pm

I have minimal wiring and soldering skills, but I ordered some UV LEDs off the internet, used an on-line resistor calculator, bought the right type of resistors at Radio Shack, and wired them in parallel to my bike's front-wheel generator to power a bunch of LED-infused pingpong balls I placed on my bike. You could do the same, just use a rechargeable 6V Lantern battery. I bet you could power a nice sized string all week for about $20?

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Post by trilobyte » Wed Jul 11, 2007 9:58 pm

Thanks for the info, Teo.

I thought I had read someplace about using speaker wire for running LED's. The poster had basically run a length of speaker wire, then used a needle to poke holes where he/she wanted to stick the LED lights. Once everything was done, a resistor calculator had been used and it powered up successfully. Of course, since embarking on the project I can't find that article for the life of me. Can anyone tell me if I can use speaker wire for such a task? It'd be fairly easy for me to get a spool of the speaker wire, a bunch of LED's, and go to it.

~Trilo~

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Post by robotland » Thu Jul 12, 2007 6:06 am

Sure you could...I recall seeing that idea somewhere too, but have forgotten where. Another "self contained" lighting concept is to use solars, either hacked or unhacked. If you're going for "mood lighting" along the length of your craft, you could simply install 'em at reasonable intervals. I've created some interesting lights by disassembling the lamp housings and extending the length of wire from the solar panel to the battery/LED cluster, although you could just as easily (by which I mean "sort of " easily) extend the LED leads.
Last Xmuz I picked up a TERRIFIC miniature string of white LEDs at Target- Ultrabright, clear white, 2AA-powered. Wish I'd gotten more. Something like that'd be good for hull-lighting too.
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Post by fluffernutter » Thu Jul 12, 2007 10:07 am

Is this the article you were thinking of?

http://www.breskin.com/led1.htm

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Post by trilobyte » Thu Jul 12, 2007 12:45 pm

Not the specific one, but it's essentially the same project.... THANKS!

~Trilo~

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Post by Teo del Fuego » Thu Jul 12, 2007 2:53 pm

and here's a real good resistor calculator

http://led.linear1.org/led.wiz

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Post by gyre » Thu Jul 12, 2007 3:28 pm

I would use luxeon leds or fluorescents bounced on the side of the vehicle.
Illuminating the shape of a vehicle is much more effective than point source lighting.
I suggest using diamondstripe reflective material too, if you can fit it into your design.
Art cars are required to be visible from all directions to the most stupid of pedestrians.
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Post by Teo del Fuego » Mon Nov 26, 2007 4:09 pm

Teo del Fuego wrote:I ordered some UV LEDs off the internet, used an on-line resistor calculator, bought the right type of resistors at Radio Shack, and wired them in parallel to my bike's front-wheel generator to power a bunch of LED-infused pingpong balls I placed on my bike.
Maybe you electrical engineers smiled knowingly when you read this...Yup, I eventually burned out my LEDs because I deena use a bridge rectifier to convert the AC from the bike generator into DC. a 6 volt battery was the better solution after all.

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Post by mdmf007 » Mon Nov 26, 2007 8:07 pm

should be DC power coming out of the bike generator - I am thinking its the unclean (fluctuating) voltage levels. unless the generator has a teenie tiny invertor built in or a regulator its going to change as the speed increases or decreases. There are some pretty small voltage regulators on the market you can get at a junkyard. That shoould smooth out the spikes. You can also set the voltage output down so you dont exceed the LED ratings.

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Post by stargeezer » Mon Nov 26, 2007 8:51 pm

The output of the generator will have a high ripple content. With a filament type bulb, this is not a problem as the current draw is high enough to keep the voltage spikes down. The frequency of the spikes will vary with speed, but you don't need to worry about the frequency, just the amplitude of the spikes. If you were designing your LEDs with a ballast resistor for 12v, the peaks coming from the generator would be significantly higher than that. This would create large current spikes in the LEDs, which would cause them to fail. If you could measure the voltage spikes and design for that you would be fine. Just at a guess, with a low current load I could see the spikes hitting at least 24v.
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Post by Teo del Fuego » Tue Nov 27, 2007 9:30 am

mdmf007 wrote:should be DC power coming out of the bike generator
Now Im REALLY confused...my 83 year old electrical engineering Dad suggested that the bike generator was putting out AC, and I guess that made sense to me because the juice is made by a spinning coil inside a magnet. (forgive my basic ignorance.)

So, educate me pretty please, is it not true that electricity made from chemical reactions is almost always DC while electricity made by a generator is AC?

Can I tell which my bike generator is outputting with multilmeter?

Currently Clueless

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Post by Teo del Fuego » Tue Nov 27, 2007 9:33 am

mdmf007 wrote: You can also set the voltage output down so you dont exceed the LED ratings.
I had 10 LEDS in series, or was that parallel?, with resistors calculated for 6v power source. They worked fine for a couple of days but eventually, one by one, failed.

Obviously, I haven't tried re-configuring yet, and any help you fine knowledgeable people would help a lot!

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Post by theCryptofishist » Tue Nov 27, 2007 10:09 am

Im no ace at this stuff, but I don't think the way it's made is the difference between ac and dc. Cause what would an inverter be/
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Post by Teo del Fuego » Tue Nov 27, 2007 10:27 am

this just in from the masters at Google:

*****************************************************
There is no such thing as a DC generator. All power generation (except chemical or solar batteries) uses Faraday's law of induction. This law requires a CHANGING magnetic flux to make the voltage that pushes the current. The only way to keep the magnetic flux changing is to reverse it periodically, which also causes the voltage and current to reverse. Thus, it gives AC current.

What is called DC generator is really an AC generator with some extra electronics (or sometimes just special "brushes" on the motor shaft) to convert the AC into DC. (Look up "full wave rectifier" and "Zener regulator" if you want to see some details of how this is done.)

*****************************************************

So, my bike generator makes, by definition, AC as I had guessed. BUT what is still unknown is whether my bike generator has the additional fixin's to convert its output to DC. Since the bulb that came with the generator is the same bulb as you'd find in a flashlihgt, I had assumed at first that I was dealing with DC. My Dad may have steered me off course momentarily by assuming the generator had an AC output.

Funny, I loathed math as a kid, but now that Im in a profession far removed form numbers, I have developed a growing passion for electronics and science. Burning Man really sparked that interest! If I were a science teacher I'd cart my class to BUrning Man. Of course, it would be the last class I ever taught.....

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Post by mdmf007 » Tue Nov 27, 2007 2:15 pm

I was assuming it is the same type of generator I had on my bike, little silver thingy with a flip lever that drops a ribbed wheel onto the tire to rotate the generator. This is a dynamo - and generates DC current as it is a simple device, and was one of the first generators invented.
It works by pulsing DC current. With a commutator - you can change the flow.

Series wiring is where the power flows though one bulb to the next. One bulb burns out and the whole circuit dies.

Parallel is just that - would be wired like a ladder, with the rungs being the individual LED's

Since LED's draw so little power I am thinking a battery would be the simplest way to go - a small motorcycle battery weighs about 5 pounds, and can be mounted anywhere on a bike. I would be willing to bet that it would last all week before neding more juice.

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Post by Toolmaker » Tue Nov 27, 2007 2:45 pm

Teo del Fuego wrote:Can I tell which my bike generator is outputting with multilmeter?
Yes

There is a small book / pocket ref in auto parts places that will show you the basics in its use.

edited to add:
http://www.makezine.com/blog/archive/20 ... _tuto.html
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Post by stargeezer » Tue Nov 27, 2007 5:06 pm

I will try to help on a few points here.

Flashlight bulbs are not sensitive to polarity, they are just a small version of an incandesent bulb used in the house (which I hope you have switch to CFL but that is another thread). The voltage heats a filament which produces light.

A basic generator will output AC and can be converted to DC several ways, some internally.

An LED only allows current to flow in one direction, thus it is polarity sensitive. Unless the voltage is an extreme, an LED connected to AC will light for half the time, and be off for the other half of the cycle, but this time is so small that your eye will not detect it.

LEDs are extremely sensitive to excessive current.

If your generator was rated for 6v, that is with the load of the normal lights which could draw a couple of amps. For 10 LEDs, the total current draw would be only a couple of tenths of an amp. This difference in current draw allows the output voltage of the generator to exceed 6 volts and this provides higher currents which I believe took your LEDs out.

Since you had 10 LEDs connected, they must have been connected in parallel, for a series string that long you would have needed a higher voltage.

As suggested by others, a battery would be more consistent and predictable. The output from the generator would be dirty enough that a filter would really help. The problem is that you must design for the spikes the generator creates, not just the average voltage.

If you really want to use your generator, PM me and I will try to walk you through the details.
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Post by AKAparttime » Tue Nov 27, 2007 6:16 pm

Howdy all.... been useing LED strips from this place.. AGIlight
I put 2..6in strips in a small box on my bike as a head light
they run on 12v and last all week+[/url]

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Post by mdmf007 » Tue Nov 27, 2007 6:56 pm

Use a battery - If not your lights go out the second you stop moving. A bettery would keep em lit while parked, and ith that small a draw. one battery would keep em lit all week at night

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Post by Valkyrie » Tue Nov 27, 2007 6:58 pm

What I'm thinking mdmf007 is looking at is a rectified generator, (lets not get into the semantics of generator/dynamo/whatever. It's all the same thing for our purposes.) although the loss from rectification is probably not worth it because if you're running incandescents, as stargeezer points out, they don't care what direction the current is coming from or how fast.

If you want to run anything other than a dumb light bulb it gets funny. The stuff coming out of the wall is a nice 60 hz regular sine wave. On your bike, you're running at the frequency your bicycle tire spins. It's a nice sine wave since that's the way it works, but probably not a stable frequency. For anything other than incandescents, rectifying it (turning it to DC) makes sense because then you can do some fun and interesting things with voltage regulation much more easily to keep those lights burning even when you stop for someone to pass.

LEDs are most efficient with DC, but as stargeezer pointed out, they'll work with AC too. Some diodes (which LEDs are a sub-class of the light-emitting variety) are not very well built for reverse currents and will break down if you run them backwards. It's been years since I paid attention to that, so it might be a thing of the past.

Chances are you have no voltage regulation at all on your generator. Do the lights go off immediately when you stopped moving? If it's a cheapie sort of generator, where the output directly drives the light, then chances are it's spiky all over the place.

Either way, a nice rectifier circuit that provides a little regulation (capacitance: it takes the spikes out!) will go a long ways.

(And yes, I DO have a BSEE, so I'm not totally talking out my ass.)
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Post by mdmf007 » Tue Nov 27, 2007 7:18 pm

Valkyrie hit it on the nails head, and I am sure he would agree - just hook it up to a battery and be done with it. We could walk you through wiring up generators, solar panels, and circuits to smooth and even out the flow but you dont need it.
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Post by Valkyrie » Tue Nov 27, 2007 7:32 pm

Uh, dude. That's pretty much the opposite of what I said - if you just slap it on there your lights will all burn out, like he experienced...


Oh, and despite the fact that I'm an engineer-geek, I'm a girl-type person. grin
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