recycled led lights question

11 years ago

I went to a couple of home supply resale stores and found several LED lights I am curious about. One is labled LED Light Bar and is about five feet long. It is about 3/4" wide and 1/2" thick and has no power supply built in. It says that it requires 24V DC, and has a pair of wires coming out of one end, one black and one brown. What is the best way to wire it? Without input from any of you, I would measure the resistance between the wires, to determine the polarity, and then connect a 24 Volt power supply to it, connected in the high resistance direction (I think that LEDs would be be damaged if connected with the wrong polarity). Do I also need a current-regulating circuit? I purchased three of these lightbars.
The second type, from a different store, is labeled "Lightolier AGS 2-lamp indirect and integral Low Voltage Track". It is 4 feet long and hangs from the ceiling. There is a pair of fluorescent tubes directed up, and a low voltage monorail style track with Xenon heads pointing down. I looked at the Lightolier website and found this product, but without the track. The store has four of these at $40 each, but two are missing parts of the heads. I contacted Lightolier and their NYC rep said that these heads are not available anymore.
I need to decide if it is worth the gamble to purchase them before I leave for home Saturday AM. The store has one mounted and turned on.

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Comments (4)

David
11 years ago
Resistance measurement does not show connection polarity.

Since LEDs are diodes, they will not light up if connected incorrectly. They will not be damaged.

The power supply will probably need to be a MLV (magnetic low voltage)
mtvhike
Original Author
11 years ago
A multitester does have polarity so a diode will have high resistance in one direction and low resistance in the other. So from what David said the property polarity is the low resistance (high current) one. The second part of my question is "does the 24V power supply have to be current regulated?" If it is connected in the wrond direction, then little current will flow, hence no damage, just no light.
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mtvhike
Original Author
11 years ago
Success! (sort of). I connected my lights to a laboratory DC power supply and they started to light up at about 18 Volts, with full brightness at 24 Volts. At that voltage, they were drawing 1.5 Amperes, so a total of 36 Watts, which is what was marked on the unit. I now have the problem of getting a suitable power supply I went to HD, Radio Shack, and two electrical supply houses. None had a 24 volt DC power supply, although one of the supply houses showed me a WAC power supply which they said would work. It was labeled 24V AC, but the counter salesman said "it was AC-DC", which I don't believe. However, will LEDs work on AC?
mtvhike
Original Author
11 years ago
Update -
I purchased some 24 volt unregulated DC power transformers (unregulated because I wanted to use dimmers). This works fine - sort of. I had a couple of unused dimmers and connected them. All are fairly old, and none are probably designed for LEDs (or CFLs). One was terrible, the second worked OK but buzzed a little. I then used a Variac and that works perfectly, but can't be used in a domestic situation. So, I need to find a dimmer rated for both LEDs and magnetic transformers.