LED Tester: I read on this thread (& seen a photo) of 'C' cell battteries being used to test the new LED's. Should I use 2 C cell batteries (3 volts) without a load resistor thereby activation the LED at the knee of the curve or should I use three batteries & if so what is the recommended load resistor? Thanks (again), Jim
DIY LEDs - The write-up
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james3370
Premium Member
i was doing a moonlight bar (back in before the split) & i was using cheap chineese knockoffs that i got off ebay. after wiring them all up, i got nothing, so i cut the wires apart & started testing the LEDs individually w/ (2) AA batteries. i took a small wood clamp & clamped a wire on each end & the 2 batteries together. that left me both hands free w/ a wire in each hand to touch each star pad
i ended up finding the problem....2 of the LEDs were soldered on the star backwards, so the polarity was reversed from the imprinting on the star :mad2: i resoldered them all together correcting the polarity & it worked
james3370
Premium Member
2.5" side to side is about the limit w/out getting a "spotlight" effect, but should work good. now if using optics, 1.5-2" would be a better spacing choice
rlhornback....check the ultimate led guide thread by evil over on nanoreef.....he has done several of these & there are quite a good bit of these fixtures over there. the thread + his advice will get ya pointed in the right direction as far as spacing & optics choices for your build
Skeptic_07
New member
we need this:
http://www.trossenrobotics.com/store/p/3415-LED64.aspx
but with output of 1000ma. Does it exist?
http://www.trossenrobotics.com/store/p/3415-LED64.aspx
but with output of 1000ma. Does it exist?
While I'm on a roll, here is another question. I'm going to screw (self tap) the stars and have plenty of ss (stainless) #6's only to find out they are marginally too big, so I'm planning on #4's but the local stores have nothing smaller than #6. Has anyone used self tapping screws and if so what size? [I also plan to use a nylon washer to avoid excess pressure on the star (either installing or theremal expansion)]. Jim
forrestcook
New member
I hate to ask again so quickly, but I'm trying to order asap (found some liquid money in my acct) and I need to know if 24 will work for a 40 breeder or do I need the full 36?
aiannar974
New member
So - How are the corals doing?
zack200513
New member
I want to try this on my 46 gal bow front. Trying to figure out what all I would need, amount wise, for this. I have a MH fixture and would love to go a cheaper route. This is a great thread packed with great info. Doesn't look to hard to do, the only thing that i don't quite get is the dimmer. I will continue to research that though.
yupgopotty
New member
I'm using 1" in between LEDs and 40 degree optics. My tank is only 13" deep so I put the system 4" above the tank, and the color at the bottom (roughly 17") is beautiful. I don't know how deep the light would penetrate but others have used no optics on their tanks and it's worked just fine, so I'm guessing a 40 would not be a problem going down 30". Anything under 40 and you always run the risk of creating spotlights everywhere.
zack200513
New member
Thanks for the info! I just need to figure out the how wire it all up.
der_wille_zur_macht
Team RC
Zack, researching how to wire it all up (with respect to dimming) will depend totally on which solution you go with, as each driver has different dimming capabilities.
The easiest solution, for the uninitiated, is to use a driver that simply requires a pot to dim, i.e. a buckpuck. The next most complicated would be a driver that requires a variable DC voltage, i.e. the "pot dimmable" mean well drivers - these require a pot and an external 10v power source, which can come from a wall wart wired to the pot. The most complicated solution (though still not really that bad) is a driver that requires PWM to dim, i.e. the PWM dimmable mean wells, or some of the DIY drivers being used. These require a PWM signal from a microcontroller or a DIY PWM generator, which can just be a 555 timer chip, a pot, and a few caps.
The easiest solution, for the uninitiated, is to use a driver that simply requires a pot to dim, i.e. a buckpuck. The next most complicated would be a driver that requires a variable DC voltage, i.e. the "pot dimmable" mean well drivers - these require a pot and an external 10v power source, which can come from a wall wart wired to the pot. The most complicated solution (though still not really that bad) is a driver that requires PWM to dim, i.e. the PWM dimmable mean wells, or some of the DIY drivers being used. These require a PWM signal from a microcontroller or a DIY PWM generator, which can just be a 555 timer chip, a pot, and a few caps.
Skeptic_07
New member
I was talking to a good friend of mine who is an electrical engineer about help with one of these projects. He was telling me that buckpucks are not needed and that if, for example, i had a power supply that output 12v i could just hookup strings of 4 LEDs 3v each until i used most of the amperage supplied. At least, I think thats what he was saying.
edit: also are these good to use? http://www.dealextreme.com/details.dx/sku.15943
edit: also are these good to use? http://www.dealextreme.com/details.dx/sku.15943
der_wille_zur_macht
Team RC
Skeptic,
That is more or less true, but there are a LOT of caveats, and the LEDs we are using are both expensive and not very tolerant.
LEDs work in such a way that they have a functional curve that describes how much current they will pull at a given voltage. A Cree XR-E might be spec'd to pull about 1A at about 3.9v, for example. So, give it exactly 3.9v all the time under all conditions and you'll be fine. However, you need a way to lock in a very tight control over that 3.9v Get the voltage a few tenths higher than it should be, and poof. A few tenths lower, and you'll have a tiny fraction of the output. And, of course, the 3.9v spec is just an average, and you might get a batch that does 1A at 3.8v, or 4.0v, so you'd have to experiment to get it right. And, you'd have to hope that your power supply had very little ripple and didn't fluctuate with temperature or load changes.
In other words, if you literally tried to hook up 4 of those 3v LEDs to a power supply labeled as 12v, you'd most surely be unhappy with the result. Hence, most people decide to use a constant-current driver, such as a puckpuck or mean well (or DIY'd.) A constant current driver basically monitors the current flowing through the LED array, and adjusts the voltage up or down as needed to keep the current at the specified value, despite changes in temperature, load, or other environmental conditions.
The LED you linked to is OK to use, it's basically a very slightly more efficient (but slightly more pricy and harder to get) version of the Q5 XR-E most people are using. Also, it's the WG color bin, while the WC color bin some vendors have is probably ever-so-slightly more desireable.
That is more or less true, but there are a LOT of caveats, and the LEDs we are using are both expensive and not very tolerant.
LEDs work in such a way that they have a functional curve that describes how much current they will pull at a given voltage. A Cree XR-E might be spec'd to pull about 1A at about 3.9v, for example. So, give it exactly 3.9v all the time under all conditions and you'll be fine. However, you need a way to lock in a very tight control over that 3.9v Get the voltage a few tenths higher than it should be, and poof. A few tenths lower, and you'll have a tiny fraction of the output. And, of course, the 3.9v spec is just an average, and you might get a batch that does 1A at 3.8v, or 4.0v, so you'd have to experiment to get it right. And, you'd have to hope that your power supply had very little ripple and didn't fluctuate with temperature or load changes.
In other words, if you literally tried to hook up 4 of those 3v LEDs to a power supply labeled as 12v, you'd most surely be unhappy with the result. Hence, most people decide to use a constant-current driver, such as a puckpuck or mean well (or DIY'd.) A constant current driver basically monitors the current flowing through the LED array, and adjusts the voltage up or down as needed to keep the current at the specified value, despite changes in temperature, load, or other environmental conditions.
The LED you linked to is OK to use, it's basically a very slightly more efficient (but slightly more pricy and harder to get) version of the Q5 XR-E most people are using. Also, it's the WG color bin, while the WC color bin some vendors have is probably ever-so-slightly more desireable.
Skeptic_07
New member
Thanks wille.
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