LED's require correct polarity - Page 2 - Fiberglass RV


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Old 06-30-2015, 09:24 AM   #15
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I seem to recall that someone posted awhile back that they purchased a box of inexpensive LED's in bulk off the internet and only some of the bulbs had reversed polarity. Resulting in some of the bulbs worked fine in one light while a couple of others from the same box, did not in the same light without the wiring being swapped. Which would suggest to me that perhaps it was an error in manufacturing process. Due to the low costs of the bulbs it would be a good bet there was little quality control. ;-)
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Old 06-30-2015, 11:14 AM   #16
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I seem to recall that someone posted awhile back that they purchased a box of inexpensive LED's in bulk off the internet and only some of the bulbs had reversed polarity. Resulting in some of the bulbs worked fine in one light while a couple of others from the same box, did not in the same light without the wiring being swapped. Which would suggest to me that perhaps it was an error in manufacturing process. Due to the low costs of the bulbs it would be a good bet there was little quality control. ;-)
There is always plenty of "cheap junk", and the word is: buyer beware, but in my case polarity reversal was in the wiring of the fixture, not the LED's. I think in general they are getting not just cheaper, but better. I hope I can say in a few months that I timed the market well.
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Old 07-09-2015, 03:23 PM   #17
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In the interest of making my TV's lighting control module happier I've been changing the exterior lights on our '92 casita over to LED.

Discovery #1 - the polarity thing - the side marker sockets in back at least were wired backward. As I was bodging in some #194 LED replacments I had lying around (wedge bases) my solution was just to change which wire went to the base contact and which went alongside the wedge and was pinched to the side contact.

Discovery #2 - They got the tail lights right, but my cheapie 1157 LED replacements were wired OK for polarity but backward for brightness. I had to unsolder the bulb base, rotate 180, and then resolder. Also fixed a cold solder joint on one plank of the 'christmas tree' while I was at it.

Result: they're nice and bright and current draw is about 80% less than it used to be. It'll be better still once I get the front side markers replaced as well. I'd already had the soldering iron out anyway making my freetastic fan, so the hassle factor was greatly reduced over what it might have been.

Conclusions: 1. Check the polarity at the sockets. 2. cheap LEDs are indeed cheaper for a reason.
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Old 07-09-2015, 07:41 PM   #18
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I noticed that a number of people are changing the marker lights, brake lights or directional bulbs to LED's. Is it for brightness and longevity?

My motivation to go with LED lighting inside the Scamp is to have my battery last longer when camping without shore power. While on the road, the LED lights or incandescent will make no measurable difference. Is there something else to consider other than the above mentioned brightness or longevity?
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Old 07-09-2015, 09:54 PM   #19
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Is there something else to consider other than the above mentioned brightness or longevity?
Absolutely! The exterior bulbs in my Casita looked like they might be the originals from 1992. Longevity (of the bulbs) isn't an issue.

One factor is response time - if you hit the brake lights or turn signals, LEDs are about 300 milliseconds faster to light up. That doesn't sound like much, but human reaction time under ideal circumstances is in the 600-800 ms range. Anything you can do to clue in the human behind you sooner is a good thing. That's why high mount brake lights were adopted - they were documented to reduce rear-end collisions because the people following noticed the lights coming on sooner.

But for me, what is specifically an issue is the lighting control circuitry on the tow vehicle. Back in the day you could just hook the running and signal lights up to the TV wiring and you were done.

Then along came electronic lighting controllers. Now there's a pretty strict current limit. Go beyond it and you cook something, the computers get unhappy, or both. All this is fine if you have the factory tow package - I don't. Uhaul will sell a little box full of relays that switches power from somewhere else with signals from the tail lights. I've avoided that because it's one more thing to break, and they're kind of expensive for what you get.

My TV is an old enough design that it expects to use incandescent bulbs for everything itself. That's the good news, as it means that it has a pretty stout current capability. The bad news is that exceeding design specs by 50% by adding more bulbs isn't good for longevity.

The off-the-shelf solution is to put some LEDs in. Loads on everything are suddenly just about where they were before the trailer was plugged in, but the trailer is actually brighter than it was with incandescents.

No filaments to break is just another bonus. My total outlay on LEDs is about $5 right now - I bought them straight from China. Minor QC problems are figured in the price...
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Old 07-09-2015, 11:47 PM   #20
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I noticed that a number of people are changing the marker lights, brake lights or directional bulbs to LED's. Is it for brightness and longevity?

My motivation to go with LED lighting inside the Scamp is to have my battery last longer when camping without shore power. While on the road, the LED lights or incandescent will make no measurable difference. Is there something else to consider other than the above mentioned brightness or longevity?
One has to be careful about LED tail lights. The very bright day time, full sun lights are nice, but at night they blind the driver behind you. There are laws and rules about how bright tail lights can be at night. Some car manufacturers have gone back to incandescent because of this. They need to incorporate some sort of dimmer for night time use.
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Old 07-10-2015, 12:44 AM   #21
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Interesting Byron, but do you really think anybody is going to be stopped because their brake lights are too bright? All I want is if the guy in front of me hits the brakes is that they work.....even if they are way bright .
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Old 07-10-2015, 06:14 AM   #22
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My Trillium came with Bargman LED tail lights. They work well and I'm happy with them. But when one failed the whole unit had to be replaced. $40. While LED's may have a longer life they require additional electronics which adds to the possibility of failure. Typically these are sealed and unrepairable. As you drive around note the cars that have LED tail lights and imagine what the unique sealed unit will cost at the dealer as Napa won't carry them. Raz
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Old 07-10-2015, 07:56 AM   #23
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Very interesting comments, thank you, all.

One very obnoxious thing I noticed about some LED lights years ago was the strobe effect. That may have been an attempt at dimming them by means of PWM (pulse width modulation), I think. Looking straight at them the effect is not noticeable, but sweeping the field of view shows the comet tail, like the comet cursor on the computer screen. With lights that are steady, there may also be a tail, but it is less disturbing.

Years ago I remember there were some discussions about a three-mode brake light:
power flow to the wheels (foot on gas) - no light
idling/coasting - some color (?)
braking - red

That would definitely cut down the reaction time dramatically, much more than the LED light curve response. What happened? Government inertia?
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