Superflux LED strips

[justDIY]

I recently built four of these strips from PCBs I had made some time ago.

Each strip holds six 200mW superflux LEDs wired in series.  Each strip also contains daisy chain connectors for attaching the strips in parallel to a power supply.

I have used zip-ties to fasten each strip to a piece of wood, which I've suspended above a fishtank as temporary lighting.   I needed a light that would let me see the fish and give them enough light to recognize a day/night cycle, but not so much light as to promote any type of algae growth.

Using a LM317 configured for constant current drive, the array draws about 4 watts




the strips have a lot of copper left on the solder side, to help keep the LEDs cool.   I'm not too worried about it, as they are installed inside my lighting canopy, which has forced air ventilation that runs 24x7 to keep humidity from eating the woodwork

I will try to get a picture of the four strips on their board - it is a bit ackward to photograph something that is 4ft long but only 1.5" wide.  I tried taking pictures of the tank, but my camera won't do it without a flash, and well, the flash sorta defeats the whole purpose.  it's just 55 gallons of warm water with a dozen or so tropical fish in it

[Rob]

Nice--any comments on how warm they run?

The spacing and large tracks both contribute favorably to thermal management, so this is a good example of a superflux array that takes thermal design into account. What's your target drive current?

[justDIY]

only idea I have on temperature is subjective, that they feel "luke warm" ... I'll have a compunurse layin here with those super thin thermal probes - I'll hook that up and get a hard number.

right now, as I measure it, the array draws 180 mA (rounded off - output side), so 180 / 6 = 30 ma ... whats funny is I'm using three 18 ohm resistors in parallel to program the current for 200mA.   I think I don't quite have enough headroom voltage for the regulator to meet my 200mA request - I need to look up how much overhead the 317t has; I estimate my array requires 21v (or slightly more) and my supply is only 24v

i had originally planned to run the array from a boost mode smps, supplied by 5v, but had trouble getting more than 18ma out of the converter on a breadboard.

[justDIY]

compunurse says the temperature is 38.0°C, or about 100 degrees.  point of measurement was the middle of the board, on the component side.   the temp is 13 degrees higher than the magic 25°C, so I'm probably shortening the life of the phosphors and diodes, but oh well!

I'm not using the boards in quite their designed application.   I had planned to place the leds on the solder side, trimming the leads so they rest in the holes but not protrude through them - then I could adhere the boards to a secondary metal heatsink

when I get around to it, I'll stick the probe right to the led package under the diecup and see what the temp is there, I figure that is the closest point for measurement of actual junction temperature I could make

[seanyiya]

Does it LED light really cause algae to grow??

[justDIY]

algae that I didn't get scraped off durning the cleaning has all pretty much died now

no signs of new algae growth

these lights are incredibly dim compared to even a 15 watt fluorescent I had been using.

[minimum]

If I'm not mistaken, you're using Eagle to draw your PCB's?
I have been looking for library for superflux/piranha package for a while. Did you create your own library or downloaded from somewhere(if so, can you please provide link)?

Edit: Haha! Found it! Thank You!

[justDIY]

If I'm not mistaken, you're using Eagle to draw your PCB's?
I have been looking for library for superflux/piranha package for a while. Did you create your own library or downloaded from somewhere(if so, can you please provide link)?

Edit: Haha! Found it! Thank You!

If you want the .sch and .brd files for the strips, I can post them too.... my latest revision of the strip is slightly wider, but runs a lot cooler due to much more copper coverage... the rgb version needs some work, probably more copper, it tends to heat up after extended operation.

[minimum]

Thanks but I'm going to do a taillight conversion. Will post pictures if done.

[minimum]

Messed around with Eagle tonight, here's some results:



And here's Eagle brd and sch files for it (sch looks ugly but it's functional ) in case someone needs it.

[justDIY]

not bad for a first whack, you're gettin there!

my fileserver is down at the moment, but when I get things back online, I'll post the brd and sch files for my strips, you can take a look at the methods I used for maximum copper, and / or change 'em around to fit your needs.

pretty much what I did, instead of using the route command to connect point A to point B, I used the polygon command instead ... and then you name the polygon to match the signal name connecting A and B... once you do a render, the polygons all fill in and leave just a tiny gap of between each other

[minimum]

Yes, but this method makes some really weird connects between pads and polygon.
Just look at the picture:



justDIY, I did notice similar things on your "MintLite" boards.

[justDIY]

those are called "thermals" short for thermal isolation

change -> thermals -> off

generally, you want them, especially for SMD components, since it allows the pad to heat quickly, making the soldering go a lot smoother... but for LED heatsinks, they're deffinately no good

Here's the heaviest-duty of my led strip designs brd and sch... have a look

http://projects.dimension-x.net/files/LEDStrips.zip

[minimum]

For some reason my Eagle shows polygons and all tracks on top layer and nothing on bottom layer. Something to do with different versions?

Anyway, I get the idea - I have used something similar so far: rectangles. A lot of placing the components for optimal layout and a bit ugly solution but it works well. Perfect with etching - less copper to dissolve.

[justDIY]

yes, that layout used only the top (red) layer ... it really makes no difference when it comes time to print out and etch a board.

the rectangle command can be used as well, but rectangles are not "smart" ... that is, the autorouter doesn't know about them and I believe you cannot connect them to signal layers.

I use the polygon tool exclusively for covering large areas... along with the split command as well as polygon rank, you can make some interesting things happen fairly easily.