Solar Powered L.E.D. Strand Lites..

[12vman]

First post, guys.. Great forum..

I wanna pick your brains if I could..

I bought some of these and I can't figure out how they do what they do..

Needless to say, I've torn them apart and looked around but they don't follow common sense. There is 1 NiCad (1.2 volts) that fires 100 L.E.D.'s. They appear to be connected throughout the strand in parallel. (Only 2 wires the length of the set) I'm somewhat aware of L.E.D. drivers but I can't find one that will drive that amount of L.E.D.'s at that voltage. Could these be some kind of special L.E.D.?

These things are amazing! A few hours of direct sunlight and they will glow all night! I'm impressed! I use them in my home for low lighting applications. I would like to build some of my own. (I'm off grid)

I can get the standard 5mm white L.E.D.'s by the bagfull. (3.2-3.8v/30Ma.) I've built my own light fixtures throughout my home. (Hybrid fluorescent/L.E.D.) I have plenty of 12 volts D.C. to work with. Just need to figure out how those solar lights work.. :candle:

Thanks in advance..
~Don

 

[Meduza]

The key here is that they all are connected in paralell!

That means that the voltage is still only 3.2v or something around that,
but the total current is divided between all the leds.

To "Glow" you do not need many milliamps, maybe 1.5mA per led.

2mA per led * 100 leds = 150mA

That means that any standard 150mA powerled driver could be used
to get a whole string of 100 leds to glow quite bright for quite a few hours
on a single NiCd cell, around 4 hours on a AA cell and 8 on a C-cell.
If it is a D-cell in there, these could run 16 hours on a full cell with no problems.

 

[12vman]

Thanks for the response.. :wave:

Actually they seem to be almost at total brightness. The L.E.D.'s have an inverted lens so the light shines from the sides..

I've been looking at a micro puck.. http://www.leddynamics.com/LuxDrive/datasheets/2009A-MicroPuck.pdf

Per current output, it appears this puck will only drive around 13 L.E.D.'s but the output voltage is around 8 volts. Does this mean I could have 3 strands, connected in parallel, of 13 L.E.D.'s?

Be easy on me.. LOL I've never messed with drivers before..
~Don

 

[Gunner12]

The micropuck can drive 13 LEDs in parallel. It's maximum is 8v but it usually runs around 3.0-3.7v depending on LED. 80% efficient at 3v, I'm not sure about efficiency at 1.2v.

You might also want cheaper drivers to start you off. These are $6.50 for three shipped and about 69% efficient at 1.2v(ad 70% efficient at 3v). You could probably run 10 5mm LED at spec(usually around 20mA) with the output current, even more if you under drive the LED.

This one is more efficient(post, it also has many modes, starts at low output). All measurements are at high output, 86% at 1.2v with power set to 1w(3.11v and 320 mA output, 16 5mm at spec) and 91% with 2 NiMh batteries and power set to 1.5wd(3.2v and 460 mA output, 23 5mm at spec) but they are more expensive at $5 shipped for one.

The above drivers are both larger then the Micropuck but the second one is more efficient.

Also look at this, Ugly but it will provide more light then 13 5mm LEDs and have a long runtime.

:welcome:

 

[12vman]

Thanks guys for the input. I have a lot to learn about these things.. :laughing:

Maybe I should explain a little more in detail..

I have plenty of 12 v.d.c. to work with. As I stated, I'm totally off grid and my home operates with the 12 volts direct. Most of the drivers that I've looked at uses voltages much lower than 12. My goal is to design/build some light fixtures using some sort of driver to achieve as much light as I can and use the least amount of current possible without converting to a lower voltage. I have a whole bucket full of standard 5mm white L.E.D.'s that I'd like to use up..

This is why I was curious on how the solar set operated. I figured if they can get 100 L.E.D.'s to fire with 1.2 volts, I should be able to get a whole lot more using 12 volts..

Is there such a driver out there that would work in my situation?

Thanks again in advance..
~Don

 

[Meduza]

One idea is to hook up series of 3 leds and just put a resistor in the end and drive them directly from 12v.

This way you can wire up as many as you want, and is propably the cheapest
and in fact a quite efficient way in this case.

The other solution is to use a driver of some sort.

A nFlex from Taskled.com should be able to power up 50 of these strands at full power in paralell for a total of 150 leds from 12v... if you underdrive them a little (saves LED life and effeciency goes up) you can power 65 strands @ 15mA per LED.

 

[12vman]

Quote.. From Meduza..

"One idea is to hook up series of 3 leds and just put a resistor in the end and drive them directly from 12v."

I've tried this in the past but I haven't had much luck. I operate a couple of pumps and a few relay switched devices from the battery and the induced kick back voltage fries the L.E.D.s one by one it seems. They also "flicker" with any type of voltage drop. What I have had luck with is by using a voltage regulator (LM7806/LM7809) and running 2 or 3 in series. (per voltage selection) This runs them a little under voltage with no control of the current. (no resistors) The regulator seems to stop the kick back "spike" from getting to the L.E.D.s and I can fire a bunch of sets with 1 amp.. Also stops the "flicker" issue..

Maybe I'm chasing my tail trying to get more efficiency..? :sigh:

Comments?

Thanks Again..
~Don

 

[Gunner12]

You could drive 4 Cree XR-E or any high power LEDs(I just recommended the Cree because it is one of the more efficient LEDs out right now) in series with 12v, That would be about 150-200 mA per LED, which works out to about 160 to about 200 Lumen depending on the bin code(in order of efficiency, available bin codes for the Cree, P4, Q2, Q3, Q4, Q5). You just need a good heatsink to prevent the LEDs from overheating. A CPU heatsink should be fine for 150-200 mA drive current.

A Cree XR-E/Sepul P4/Reebel 100 LED can take 1 amp power with no problem and are harder to fry then 5mm LEDs(as long as you have a good heatsink). The beam pattern would be all flood and no spot. Most good 5mm LEDs are 4-5.5 lumen at 20 mA.

Most white LEDs operate well at above 3v. Most will light up dimly(very dimly, enough to notice but usually no enough to be useful) at 2.5v.

Cheaper high power LEDs an flashlight parts here and here, If you are buying, go for the Cree(P4 bin or over)/Seoul/Edison LEDs.

This driver will run at up to 18V input and can drive up to 3 high power LEDs at 750 mA with your 12v supply.