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Old 09-20-2014, 08:20 PM   #1
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IKEA LED light strips wired directly into 12V - need resistor?

Any electricians out there?

I'm installing Ikea LED light strips (STRIBERG LED light strip - IKEA) under the cabinets in my 2003 Airstream.

The lights come with a transformer made to plug into a 110V outlet. Instead of using this transformer, however, I'm hardwiring the lights directly into my trailer's 12V system. Do I need a resistor in my LED circuit?

If it helps, the Ikea LED Driver that I'm not using is the SLT6-12VLS(UL). Class 2.
Input: 110-120VAC, 50/60 Hz, 0.14A
Output: DC12V, max 500mA, 0.5-6W
DC700ma, max 8.5V

Does the driver have a resistor built-in which I need to compensate for since I'm NOT using the 110V to 12V driver (transformer) but have instead wired the lights directly to 12V? The lights work great wired directly into 12V - I'm just concerned about premature burnout if I need a resistor and don't install one.

Your help would be greatly appreciated.
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Old 09-20-2014, 08:30 PM   #2
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If I remember my basic electronics course correctly, and, admittedly, it's been a few years, you shouldn't need a resistor. The diodes should only draw the current they need, as they're already set up to run on twelve volts... Think of it like any twelve volt device you have. It's made to run on twelve volts, current usage is built in by design. It's why you don't have to put a resistor on your car headlights... They are made to run on twelve volts.

However, if they burn out early, this advice was worth exactly what you paid for it...

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Old 09-20-2014, 09:48 PM   #3
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Nope. 12vdc is just what you need.
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Old 09-20-2014, 09:51 PM   #4
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It really depends on the headroom for voltage fluctuations that was designed into the set of lights, and you will have no way of determining that. If the lights were set to operate on 12 volts DC maximum, and the original power supply was tightly regulated and the LED's were operating close to their maximum rated current, the higher charging and operating voltage of the Airstream, (which can run from about 13.2 to 14.5 volts depending on your converter/charger and what stage it is operating at) could overdrive the LED's.

But if the original power supply was really under driving the LED's to begin with, you may have no issues at all.

I know of no way to determine the design of the original set. So, you pays your money and hope, is all I can say.
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Old 09-20-2014, 09:55 PM   #5
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^^^^Xactly^^^
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Old 09-21-2014, 12:14 AM   #6
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I put similar IKEA strip LED lights into a friend's rig for Burning Man with a 12VDC direct connection and he said that he had no issues.
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Old 09-21-2014, 06:24 AM   #7
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I think you nailed it!

Quote:
Originally Posted by idroba View Post
It really depends on the headroom for voltage fluctuations that was designed into the set of lights, and you will have no way of determining that. If the lights were set to operate on 12 volts DC maximum, and the original power supply was tightly regulated and the LED's were operating close to their maximum rated current, the higher charging and operating voltage of the Airstream, (which can run from about 13.2 to 14.5 volts depending on your converter/charger and what stage it is operating at) could overdrive the LED's.

But if the original power supply was really under driving the LED's to begin with, you may have no issues at all.

I know of no way to determine the design of the original set. So, you pays your money and hope, is all I can say.
Your answer to my original question is, I suspect, right on.

My thoughts were that these lights are probably meant to run at 12V and so wouldn't need a resistor if hard-wired in to a 12V system. It was helpful to hear that most of the responses to my question seem to confirm this and that, assuming my trailer had true 12V, I wouldn't need to install additional resistors.

However, you're also correct in that my converter does give me more than 12V. When I tested, I'm getting 13V plus. So, it makes sense to me that that how well the Ikea lights will perform in the long-term depends on how much 'wiggle room' for voltage over 12V was built into them.

Thanks to all for your helpful comments.
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Old 09-21-2014, 06:32 AM   #8
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Now that you got the technical answer you are good. I do however want to point out that for a lot less money you can get much better quality(built and optics) LED units. The Ikea fixtures are more of a novelty than good light sources. Just my two cents...
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Old 09-21-2014, 06:59 AM   #9
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Source for LED lighting

Quote:
Originally Posted by 62overlander View Post
Now that you got the technical answer you are good. I do however want to point out that for a lot less money you can get much better quality(built and optics) LED units. The Ikea fixtures are more of a novelty than good light sources. Just my two cents...
Any ideas concerning where I can get similar lights of better quality for less money? I'm using these mainly for accent lighting, but would like to have ones that are brighter and whiter (higher on Kelvin scale). The 26" Ikea lights that I'm using are only $19.95.

In doing an internet search, I found a place called lampsplus.com. Their nearest equivalent to the $19.95 Ikea light sells for over $119.95! (Orion Super Bright 25" Wide Aluminum LED Under Cabinet Light Style # W9260). That's a big difference in price, in the wrong direction!
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Old 09-22-2014, 05:04 PM   #10
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Outwater Plastics has a lot of LED units.
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Old 09-22-2014, 05:54 PM   #11
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eBay is your friend for LEDs.
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Old 09-22-2014, 07:57 PM   #12
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Reply to post # 1

About the question submit by AStreamJake, if you need resistor for Ike LED lamps. If the LED strip specification mention 12 volts DC, I may suggest to do not exceed too much this voltage. The life of the LED lamps will suffer of this "over voltage". Some additional heat will be generate and LED lamps are sensitive to high internal temperature.
I install LED Under Cabinet Lamps LED strips over the curb and road side top cabinet and the fixtures are rated to 12 Volts.
From then, I install "bleeder diodes" to "drop" the voltage provided to the LED lights.
Keep in mind that the lead acid batteries provide at least 12.7 Volts (full charge) and close to 14 volts in charge process.
The 2 diodes in series drop the voltage of 1.4 Volt. The counterpart of this set up is a power dissipation of about 2 watts by the diodes at 1.5 Amp current draw.

About the quality of the LED strips be careful to choose LED lamps with a high CRI (Color Rendering Index) of at least 75. Low CRI (less than 50) will provide poor light quality whatever the color temperature (Warm White; 2750 K, Cool White; 4000 K, Day Light 6000 + K). But this topics is an another subjectÖ

In my personal experience low cost LED drip means frequently low CRI.

See below pictures of diodes set up and batteries capacity.

Michel
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Old 09-23-2014, 05:21 AM   #13
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Quote:
Originally Posted by Papou View Post
About the question submit by AStreamJake, if you need resistor for Ike LED lamps. If the LED strip specification mention 12 volts DC, I may suggest to do not exceed too much this voltage. The life of the LED lamps will suffer of this "over voltage". Some additional heat will be generate and LED lamps are sensitive to high internal temperature.
I install LED Under Cabinet Lamps LED strips over the curb and road side top cabinet and the fixtures are rated to 12 Volts.
From then, I install "bleeder diodes" to "drop" the voltage provided to the LED lights.
Keep in mind that the lead acid batteries provide at least 12.7 Volts (full charge) and close to 14 volts in charge process.
The 2 diodes in series drop the voltage of 1.4 Volt. The counterpart of this set up is a power dissipation of about 2 watts by the diodes at 1.5 Amp current draw.

About the quality of the LED strips be careful to choose LED lamps with a high CRI (Color Rendering Index) of at least 75. Low CRI (less than 50) will provide poor light quality whatever the color temperature (Warm White; 2750 K, Cool White; 4000 K, Day Light 6000 + K). But this topics is an another subjectÖ

In my personal experience low cost LED drip means frequently low CRI.

See below pictures of diodes set up and batteries capacity.

Michel
Michel - Did you install the 'bleeder diodes' BEFORE the lights in the circuit, or are they installed AFTER the lights in the neutral wire leading from the lights? What is the difference between bleeder diodes and resistors? How did you calculate that you needed a voltage drop of 1.4V? Thanks, I'm not an trained electrician and new to wiring LEDs.
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Old 09-23-2014, 09:40 AM   #14
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Most LED lighting that I have worked with will operate in a stated voltage range, say 9-30 VDC. Look at the instruction sheet on your device to see if they specify an operational range for the DC voltage.


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