ReefEnabler
Premium Member
interesting.
but why do you think The0wn4g3's LEDs are in parallel??
but why do you think The0wn4g3's LEDs are in parallel??
DIY LEDs - The write-up
- Thread starter Soundwave
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The0wn4g3
New member
Yep, they are 100ma. I've read from a few sources, including that instructables page, the LEDs are suppose to have tiny fins on the bottom and sit above the perfboard to eliminate the need for a heatsink. That is the main reason I went with 100ma LEDs as by the perf board goof-up I still have a lot to learn about electronics - I'm not really to tackle anything that requires a heatstink (yet
). Right now there are 8 running in parallel, if I add 2-3 will the total light output increase, decrease, or remain the same? (sounds like a physics exam question haha)Like I said, these aren't near strong enough to light a tank, but they would be nice over a small refugium. The LEDs were $20 for 30x + the $3 driver so all total it was about $9 for the light.
Thanks for the tips kcress!
ReefEnabler
Premium Member
ok I understand why you'd need them parallel with that driver you got.... but help me understand something.
I thought for LEDs to be in parallel each LED needs its own connection to the + and - on the buck puck?? But when I look at your soldering it doesn't look like that to me, it just looks like the - from one LED is connected to the + on the next one just like soundwave's design.
Is this just an entirely differnet kind of driver? or does connecting all the contacts from the LEDs make them parallel? (vs just using one - and + from each?)
I thought for LEDs to be in parallel each LED needs its own connection to the + and - on the buck puck?? But when I look at your soldering it doesn't look like that to me, it just looks like the - from one LED is connected to the + on the next one just like soundwave's design.
Is this just an entirely differnet kind of driver? or does connecting all the contacts from the LEDs make them parallel? (vs just using one - and + from each?)
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The0wn4g3
New member
No, they are connected in parallel like normal. All the anodes are connected (I believe that's the side with the tiny circles on the left in the first picture, right on the second) and all the cathods are connected.
kinda like:
[driver]
|....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
the periods are just place holders.
I had to read through that instructables page quite a few times to figure out what was going on, and I still only have a basic understanding. Good reason why I'm studying to be a mechanical engineer and not an electrical
These LEDs were listed as 5mm 0.5W MultiChip White Flux LED 50Kmcd. The same seller has some 10mm .5W 100ma LEDs for sale listed at 280Kmcd. If I ran the 10mm's on the same driver would I need a heatsink?
kinda like:
[driver]
|....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
|.....|
(+) (-)
the periods are just place holders.
I had to read through that instructables page quite a few times to figure out what was going on, and I still only have a basic understanding. Good reason why I'm studying to be a mechanical engineer and not an electrical
These LEDs were listed as 5mm 0.5W MultiChip White Flux LED 50Kmcd. The same seller has some 10mm .5W 100ma LEDs for sale listed at 280Kmcd. If I ran the 10mm's on the same driver would I need a heatsink?
kcress
New member
The0wn4g3; If you add a few more in parallel the overall brightness will get a wee bit brighter since you are adding more LEDs but subtracting some current from the existing ones. LEDs are more efficient at lower current densities. That's why you would see a gain.
The place you're getting your LEDs from is in Hong Kong. How long did it take for you to receive them? It's taking mine forever.
Also their labeling is a bit messed up. All their various LEDs are labeled with nonsense like 0.5W when the LEDs may not be anywhere near that power!! So make sure you don't run That power thru any LEDs you want to see running 5 minutes later.
Example: The one you mention ".5W 100mA" That LED probably has a forward voltage of about 3V. Watts = Volts x Amps.
W = 100mA x 3V
W = 0.3W not 0.5W as advertised.
As for your 10mm's they should not need a lot of heat sinking as they are still just 100mA LEDs. Gum drop LEDs with just leads sticking out get most of their cooling with the leads. The longer the leads the happier they are. Full length leads would be the best for them.
The place you're getting your LEDs from is in Hong Kong. How long did it take for you to receive them? It's taking mine forever.
Also their labeling is a bit messed up. All their various LEDs are labeled with nonsense like 0.5W when the LEDs may not be anywhere near that power!! So make sure you don't run That power thru any LEDs you want to see running 5 minutes later.
Example: The one you mention ".5W 100mA" That LED probably has a forward voltage of about 3V. Watts = Volts x Amps.
W = 100mA x 3V
W = 0.3W not 0.5W as advertised.
As for your 10mm's they should not need a lot of heat sinking as they are still just 100mA LEDs. Gum drop LEDs with just leads sticking out get most of their cooling with the leads. The longer the leads the happier they are. Full length leads would be the best for them.
james3370
Premium Member
stu or soundwave.....opinions???
looking into ordering this one if i need it
http://www.ledsupply.com/03023-d-e-350p.php
kcress
New member
IMO that will be just fine james3370. It may be too bright actually so choosing the dimmer route is an excellent path. Wall wart and all. Good choice.
One point. You may want to use a cord wart instead because wall warts are nasty plug suckers. (You know how one wall wart can cover more than one outlet sometimes.)
One point. You may want to use a cord wart instead because wall warts are nasty plug suckers. (You know how one wall wart can cover more than one outlet sometimes.)
I'm sorry I really didn't paraphrase your statement if you look back in the thread I stated this before you did.
Your statement is correct, if and only if, you're talking about a single string of LEDs. I wasn't. I was talking about the hazards of parallel strings. If one sting changes the other string certainly doesn't continue to have the same current flowing thru it!
Your right ... what can I say it was late and I apologize.
Draw a circuit diagram and figure out what I stated. There is nothing incorrect in that statement whatsoever. If you think it's wrong you must not be understanding it or what current hogging is.
Actually if the bad string of LEDs could handle double the original current it would still work and this would be incorrect....
Don't take this wrong I am trying to help you understand this.
Draw a constant current source running two resistors. Make it a 1A source. If each resistor is 10 ohms you will have 5V provided by the constant current source and 0.5A running thru each resistor.
Now change one resistor to an 8 ohm resistor.
The constant current source will see only a 4.44 ohm load and will change its output voltage to:
1A x 4.4 ohms = 4.4V
Now you have 4.4V across a 10 ohm resistor.
4.4 / 10 = 0.44A (it now has less of the original current running thru it)
Looking at the 8 ohm resistor:
4.4 / 8 = 0.55A
The 8 ohm resistor is "hogging" more of the current.
You are totally correct with this if we are talking about resistors in parallel. but remember LEDs are not resistors, LEDs are nonlinear devices. The current is controlled by the forward voltage of the diode,it's basically like a switch. So you are right when one is shorted in one string, the other string "turns off" or very little current flows and all current flows through the other string. So I guess it doesn't matter if the LED fails in a short or open the result will be the same. If you have a large string of LEDs and one shorts the impact might not be so bad.
This is VASTLY more pronounced with LEDs and results in the chain reaction failure mode I described.
This is what The0wn4g3 will see happen as soon as one of his LEDs fails since he has ten parallel LEDs all being driven by one constant current source. [/B][/QUOTE]
james3370
Premium Member
yeah, i'm seriously considering going ahead & ordering the dimable buckpuck. even if i end up running it at 100%, it'd be nice to be able to "tone it down" on occasion.
for the plug-ins, i have those lil pigtails or whatever you call them....6" cord extensions that plug into the jack so you can plug large adapters in & not block plugs.
here are the warts i ordered btw...
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220378052899
looking at my build thread for reference, my wiring & lighting will be....
GFCIs in sump area >> dj strips >> 1 "channel" will be a heavy duty extension cord up thru stand to canopy area to top side of light drawer >> coralife dual timer power strip >> multiple lighting items & canopy fans
james3370
Premium Member
believe me, i know.....it's temp till i can get some addl wall timers or a RKL....waaaaay overbudget at the moment 
it will however be in a position to not get any water on it & will also benefit from the fans cooling the area....it is also pretty much at the very top of everything & where i am setting it up in my apt, there is a sprinkler less than 3ft away :rollface:
it will however be in a position to not get any water on it & will also benefit from the fans cooling the area....it is also pretty much at the very top of everything & where i am setting it up in my apt, there is a sprinkler less than 3ft away :rollface:
LED sselection: I'm trying to lock into a white & blue LED but realize that current specs require operating them at full power hereby sacrificing the best efficiency. The blue's also porduce about 30% the lumen output of cool white's. Can anyone shorten my homework by guideing me on selecting wither cool whites, neutral whites or warm whites? Also the cost of the LED's would dictate running at full power [2.6 watts (700ma)] rateher than using twice the number running at 1.2 watt s (350ma). The number of drivers would also be doubled at the lower amperage.
Is there much cost difference between manufacturers? Also is there a lower wattage (like 1 watt) unit that is more efficient than the 3 watt units I'm looking at from Cree or Philips?
This thread is terrific and the proper LED selection is critical.
Thanks, Jim
Is there much cost difference between manufacturers? Also is there a lower wattage (like 1 watt) unit that is more efficient than the 3 watt units I'm looking at from Cree or Philips?
This thread is terrific and the proper LED selection is critical.
Thanks, Jim
The0wn4g3
New member
I can vouch for that. Mine died after about a year. We had countless returns at the LFS I worked at. They would just died after a few months. We eventually stopped selling them.
I added 2 more LED's to the circuit and it does look slightly brighter. Seeing as it claims to be a 3W driving, I see how 10x rated .3W will be better than 8x. Thanks for the tip!
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kcress
New member
Sure The0wn4g3. Now if one fries you a while to replace it before damage will occur too your others.
james3370; You will be happy with the dimmable aspect. Without it you can do nothing in that regard. I have made LED fixtures wishing I had an easy way to dim them numerous times.
Also as you dim them they last longer. Or more importantly keep there output higher.
james3370; You will be happy with the dimmable aspect. Without it you can do nothing in that regard. I have made LED fixtures wishing I had an easy way to dim them numerous times.
Also as you dim them they last longer. Or more importantly keep there output higher.
I am really interested in trying this out but on a smaller scale. i have access to a computer power supply with 2 12v rails and 12-15a on each so amperage is no issue. how many stars would i need to get a full coverage of light? would 3 white and 3 blue cover the entire tank?
ReefEnabler
Premium Member
Wondering if somebody can help me answer a wiring question.
I would like to power (2) 700ma BuckPucks from a single 32VDC 2.2a power source.
In the datasheet there is mention that "Where DC input units more than 18" from source, a 220µF, 50V capacitor should be placed across the input terminals..."
Now this would of course be a nobrainer if it was one source and one buckpuck, but does it change things if I want to run two Pucks in Parallel? Do I just need a capacitor for each buckpuck??? Could I just wire the two capacitors in parallel then two the two buckpucks?
I would like to power (2) 700ma BuckPucks from a single 32VDC 2.2a power source.
In the datasheet there is mention that "Where DC input units more than 18" from source, a 220µF, 50V capacitor should be placed across the input terminals..."
Now this would of course be a nobrainer if it was one source and one buckpuck, but does it change things if I want to run two Pucks in Parallel? Do I just need a capacitor for each buckpuck??? Could I just wire the two capacitors in parallel then two the two buckpucks?
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