LED's a/c or d/c
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Old 02-16-2014, 01:03 AM   #1
1tank1man
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LED's a/c or d/c


Are the LED's running on A/C or D/C? The wire coming from the ballast to the fixture, is it A/C OR D/C?
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Old 02-16-2014, 03:03 AM   #2
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All LEDs are DC.
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Old 02-16-2014, 08:20 PM   #3
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actually not all. There are A/c LED's, the current is on one side and off on the other and alternate at a high frequency to look like a solid light. Led's consume D.C to produce light and are generally meant to be operated on D.C. but they will operate on A.C. However with A.C. of equal voltage the value of the current limiting resistor will have to be adjusted to achieve the same brightness. This is because with A.C. the led will only be lit when the current flow is in the proper direction. When the current flow reverses the led blocks current flow and remains unlit. Thus A.C. applied to an led will cause it to blink on and off even though at high enough frequencies it will appear to be lit continuously. To make a blinking led appear as bright as constantly lit led the current limiting resistor's value is lowered to allow more current flow causing the led to be brighter when lit. This causes a greater average light output and thus a brighter appearing led. This trick of the eye is a phenomenon known as persistence of vision. This is also the reason the led appears to be continuously lit when it is actually blinking.
There is an led type specifically meant to be operated on both A.C. and D.C. They are called Tri-color led's and as the name suggests they are capable of producing three distinct colors. They are actually composed of two led's one red and one green, wired cathode to anode and anode to cathode. This arrangement will cause the led to light up red when D.C. of one polarity is applied and green when D.C. of the opposite polarity is applied. The third color is generated by applying A.C. which alternately lights the red and green led's. The rapidly alternating colors mix visually to produce the third color, a greenish yellow. This is the kind of led used in moving dot displays that can change color.
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Old 02-17-2014, 03:44 AM   #4
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Wow. Nice little explanation. Why is it important if it is ac or dc?
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Old 02-17-2014, 01:22 PM   #5
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Quote:
Originally Posted by KenP View Post
Wow. Nice little explanation. Why is it important if it is ac or dc?
The ballast is located outside the unit. Which is a plus in the case of having D/C LED's because, the light bar itself wont electrocute you if it would happen to land in the water (use extreme caution anyway LOL). and the cord going to the light unit is then D/C current. To me, it is just a safer and more ideal way of doing things, unlike some units that have the A/C going into the unit with the ballast inside and in turn having heat build up do to the ballast (heat is the enemy when it comes to LED's.)
Also, if the ballast is inside the unit, a larger unit is needed to accommodate the ballast.
and has to be able to transfer more heat (under a hood can always be a challenge, especially those of us that have used t5's and 8's and especially halides have posed the worst problems. Without the use of multiple fans and LOTS of additional noise). I have personally used adjustable snap switches (an on/off switch that controls the fans to turn on and off at a set tempature and off about 20F cooler) and was able to keep my hoods quite cool under high heat conditions with great success, but with the additional electric use and more moneys spent, not to mention the loss of the tranquil and peacefulness of a planted tank we loose the affect with fan noise.
Sorry went on a tangent LOL- Actual A/C LEDs have a few draw backs as with any A/C device there is a loss of power which is usually exchanged for heat. True A/C LEDs can also have a shorter lifespan do to the dual cathode/anode in one unit which creates more heat. I also believe A/C LEDs (not positive) are less energy efficient. Not to mention, if one side fails you have one color that "blinks very rappidly" but will not produce the color you wanted anymore and will be half of the color it was suppose to be (In my post I describe the green/red led to produce greenish yellow, if one side fails you have the remaining side still lit)
My electronics degree is quite old (1994 associates degree in electronic engineering) and a lot has changed since the days of my knowledge base, if I am mistaken in anyway please feel free to help clarify. Part of my education still involved "tube type" with "solid state", so I'm a bit outdated LOL.
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Old 02-17-2014, 08:46 PM   #6
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While waiting for your answer from BML maybe you could answer another question. How do you think they can get 40% more light from a led with the same wattage, XB series. Do you think they over drive the leds? They did not provide the power usage difference between the two leds.
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Old 02-18-2014, 01:27 AM   #7
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thats a very good question KenP. I have the XBs coming, but there are a few ways this can be accomplished. Some of the examples I know of off hand would be higher wattage LED's with higher wattage ballasts, just a high wattage ballast, A/C LEDs (hence the first question), or possibly a double LED (two cathodes and 2 anodes in one mold facing the same direction). I am only speculating and there are other not so easy to explain answers and I am sure there are other ways I don't know that exist. I can say that LEDs have been around since the 1960's, believe it or not the tried to sell them after market for cars even back then (they didn't work very well and they were short lived but the principle of the LED has been the focus of "invention" for along time and I think it is now at a point were it has finally been engineered to be usable and longer lasting then ever before (if asked 4 years ago I would have not given this answer, as LEDs were still expensive and still did not have the capabilities of today).
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Old 02-18-2014, 01:50 AM   #8
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Thank you. Tell me how you like your XB's when they arrive.
Ken
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Old 02-18-2014, 06:52 PM   #9
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Hi there! To answer questions out of sequence...

Quote:
Originally Posted by KenP View Post
How do you think they can get 40% more light from a led with the same wattage, XB series. Do you think they over drive the leds? They did not provide the power usage difference between the two leds.
Nope, we underdrive our LEDs for greater efficiency and longer lifespan. The increase in light, which varies depending on spectrum from about 20-42%, is due to running more efficient LEDs (higher quality and more expensive, too). This means the same power draw as our Original Series spectrums but more light intensity.
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Old 02-18-2014, 07:02 PM   #10
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Quote:
Originally Posted by 1tank1man View Post
Are the LED's running on A/C or D/C? The wire coming from the ballast to the fixture, is it A/C OR D/C?
The power supply converts A/C to D/C and our LEDs run on D/C. But please...if a fixture falls into the water unplug it first and then grab it! Our fixtures are sealed to an IP66 rating so they are splash-proof and, while not warrantied to go under water, will likely survive a quick dunk. Just unplug, grab, wipe them off, and set them back up.

Cheers,

Cara
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Old 02-19-2014, 12:08 AM   #11
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Thank you Cara for your responce.
Ken
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Old 02-19-2014, 01:31 AM   #12
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Quote:
Originally Posted by KenP View Post
Thank you Cara for your responce.
Ken
I second that, Thank you
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Old 02-26-2014, 06:35 PM   #13
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Most welcome! Sorry it took a few days to get back to you...if anyone ever needs urgent replies, please feel free to call me directly at 512-383-5881. Some days i fall down the rabbithole of many, many emails.

Cheers,

Cara
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