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Old 12-05-2013, 08:31 PM
MEXANDME MEXANDME is offline
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LED Target Voltage Range

I know that on most LED's the target range is 9.0 - 15.0 volts.

Are they like halogens in that the closer to 9.0 volts the longer the expected life of the LED?

Also, in a HUB arrangement where all LED's are the exact same distance from the transformer, what is the ideal voltage at the LED?

Thanks,

Mex
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Old 12-06-2013, 08:10 AM
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Makes no difference from what I understand. As long all of your LEDs are within the minimum and maximum voltage window for those lamps.
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Old 12-06-2013, 10:53 AM
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Vince showed us some interesting results at AOLP last year where LED's actually drew less power at 15V than they did at 12V. With LED, you're best bet from the technical data I've looked at seems to be to run them as close to 15V as you can without going over. I used to try to balance my LED to 12V like I would for halogen but after looking at the actual numbers, I now start at the 15V tap and work up if needed.
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Old 12-06-2013, 12:21 PM
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Mex: I asked a similar question on here: http://www.lawnsite.com/showthread.p...m+voltage+LEDs
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Old 12-06-2013, 03:47 PM
MEXANDME MEXANDME is offline
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Gentlemen,

Thanks............that what I needed to know!

I just completed a small system ( 7 bullets) where voltage readings were between 13.6 and 13.9 off of the 15v tap.

I moved down to the 13V tap and got readings in the 11.7 to 12.0 range.

I left it on the 13V tap.


Regards,

Mex
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Old 12-08-2013, 10:50 AM
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So you didn't heed the advice of BCG and Vince. And why is that? I would recommend that you run the LED lamps at the top of their range rather than at the bottom... For the same reasons that Vince discovered. Having installed untold thousands of LED lamps over the past 5-6 years, and having suffered through many bizarre failure scenarios, I can attest to the fact that the lamps do seem to perform better, and experience fewer premature failures, when they are operated at the top of their voltage input range. "14v is the new 11.5v"
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Old 12-08-2013, 02:06 PM
MEXANDME MEXANDME is offline
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James,

Thanks for your additional reply.

I posted this thread after I completed the 7 light system. That system is what triggered me to ask my questions.

I will be near this customer location week after next and plan to move it back to the 15V tap.

Thanks as always!!!!

Mex
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Old 12-08-2013, 04:18 PM
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Quote:
Originally Posted by bcg View Post
Vince showed us some interesting results at AOLP last year where LED's actually drew less power at 15V than they did at 12V. With LED, you're best bet from the technical data I've looked at seems to be to run them as close to 15V as you can without going over. I used to try to balance my LED to 12V like I would for halogen but after looking at the actual numbers, I now start at the 15V tap and work up if needed.
I believe the behavior of LED circuits vary according to circuit design, but I found the following relationships in my studies:
  • Wattage increases with increased voltage (power bill goes up)
  • Volt-Amps increase with increased voltage (need more space in wire and transformer)
  • Power factor decreases with increased voltage
  • Amps decrease with increased voltage
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Old 12-08-2013, 05:26 PM
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Steve, that is specifically vague. How about sharing the actual data from your studies?

1: Wattage increases with increased voltage. (Thanks Mr. Ohm) True but since we are generally talking about 4-5 watt lamps, a slight increase of 0.25w or so is going to have virtually no affect on power bills as we all pay by the KW/H.

2: Va increases with increased voltage. Okay, but again we are talking about relatively tiny increases here. An additional 1 volt at the lamp results in exactly how much increase in Va? Considering that most of us are still installing 300W transformers, with a growth in the past year or so of use of 150W, this on zones that are typically in the 30 to 70 watt load range... there really is no real world need to worry about using bigger transformers or more wire. Its all relative.

3: PF decreases with increased voltage. Ok here I dont have the necessary knowledge to debate. I was of the opinion that PF was static and a function of how the driver was designed and assembled. If you have more specific info on how voltage alters the PF of a driver please share it, I for one would like to learn more about this. How drastically does increased voltage affect the PF? If you are using a quality LED lamp, with say a .9 PF, does the increased voltage reduce the PF by a significant amount, or just marginal as per the W and Va above?

4: Amps decrease with increased voltage. Yes, and that is the point. By increasing the voltage to near the top of the LED lamps rated range, you are decreasing the amperage running on the circuit and through the driver circuit. This seems to be the culprit of many driver failures when operating the lamps at the bottom end of their voltage input range, thus at relatively higher amperage. But again, when you look at the data that Vince supplied last year at the AOLP conference, the actual numbers are relatively small, even when the graph shown looked very dramatic. (You had to examine the x&y scales very carefully to see 'into' the graph's picture).

Light on...
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Old 12-08-2013, 09:49 PM
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I have used several Vista 150 watt transformers with LED systems this season.
They come with 12 and 15 volt taps. So is the consensus that I should go back and change all my main runs to the 15 volt tap if I had used the 12 volt tap resulting in readings of 11.6 - 12 volts at the lamps under load? I don't have a cost objection to making these service calls.
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