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mejunkhound 11-01-16 08:50 PM

75 cent 50W LEDs! Shipping included!!
50 watt ebay LED.

Got 10 of these off ebay for 75 cent to $1.12 each, shipping included!

Tried out 2 of them today, look to be pretty good, unbelievable low price!

Anyone else tried them ? I'm going to mount on old sliding door aluminum extrusions for heat sink, and see how they work for floodlights.

Will take some pic when I have them mounted.

jeff5may 11-02-16 12:50 PM

Please post a link. I think I know what you're talking about, but there are so many shapes and sizes of these things that it's impossible to know which one.

Cree has been a pioneer in the high-intensity LED lighting industry, and forged the way for a gaggle of knock-off manufacturers to try and follow. A decent portion of the lighting market customers are not interested in high-intensity light sources, due to the premium price. Many manufacturers tried and failed at producing high-power chips that wouldn't literally burn up quickly, so they began promoting medium-intensity chips that were much cheaper.

These "inferior" manufacturers were successful at making "chip on board (COB)" arrays that were (and are) much cheaper than the Cree "star" emitters. They were so successful that the entire LED lighting industry experienced severe price erosion. As a result, Cree changed its business model and teamed up with a couple of Chinese manufacturers. Rather than fight over patents, Cree signed cross-licensing agreements with Epistar and Lextar. Cree invented most of the technology and leads the high-power production, and the other two take care of the medium and low power sectors. Now, they all source each others' products. Cree now outsources the manufacture of most of its chips to these Chinese companies under license.

For DIY light fixtures, you can pack a lot of light output into a pretty small amount of space using the "medium intensity" Epistar modules. I have found I like the "natural white" color temperature in the house, and the "cool white" in the workshop.

jeff5may 12-23-16 03:55 PM

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I just got some more driver boards for these high-power LED stars to play with:
New 10W Constant Current LED Light Chip Efficient Driver Fit Supply DC9-24V

Under $1 each with free shipping. In case the fleabay listing goes away, here is another on alibaba:

These little gems are pretty tinkerable, despite the low price tag. There are a lot of flavors of these little postage stamps for whatever power source you need to connect. I was planning on using the thing on a 10W chip LED in a car, so I got a 12VDC compatible board.

This family of driver boards is based on the PT4115, a single-ended primary-inductor (SEPIC) converter. The chip is good for lots of other things besides lighting LED's, but I don't care about that. What I do care about is that these little buggers are good for up to 30 Watts (max at about 1 Watt per input volt) of power source, are dimmable, and can easily be warped to work off of AC or DC with very little trouble. Plus they are teeny tiny and don't generate heat doing the job.

Here's what another of these boards looks like:

Here's the circuit schematic for these buggers:
Depending on how the maker stuffs the board, individual component values may vary. Also, the chip is available in 6 or 8 pin packages. The datasheet tells all about what components do what and how to change values to suit specific needs. They are commonly available in 1W, 3W and 10W max output power to suit those sizes of LED chips.

As they ship, these boards are not rigged as dimmable. This functionality is easily tapped into by tacking a jumper wire to the DIM pin. This pin has a 200k pullup resistance tied to a 5VDC reference inside the chip. For analog control, the pin is pulled below 2.5 VDC to dim the output. The output power is linear, with zero output below 0.5VDC and max output at or above 2.5VDC. For digital control, the DIM pin is fed a pwm signal that pulls the pin low to dim the output. The chip can take 3.3V or 5V logic signals, and is linear with respect to duty cycle.

In the past, I have used these PWM boards with these high-power LED chips with great success. For testing, a 10K NTC thermistor can be attached to the LED chip (and its heatsink) to limit the max temperature. I tied the thermistor between the DIM pin and ground, and a 27k resistor between the DIM pin and the + pin of the big capacitor. As the LED heats up, it dims, both saving the LED chip and giving a visual indication of heat soak vs intensity. I found that the NTC balances out about right at the point where the heatsink is almost too hot to hold onto, but not quite. For the daring, a smaller resistor value will make the thermistor balance out hotter.

jeff5may 12-27-16 09:56 AM

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There are good reasons I am writing about the smaller chip LED's. First and foremost, they are more efficient than the higher wattage packages. The light intensity that is emitted for the 1 watt beads is comparable to that of a standard fluorescent lamp, and the 3 watt beads compare well to the T8 fluorescent tubes. The 5 and 10 watt chips are brighter than fluorescent fixtures, and are too bright for "soft lighting" in many applications without some sort of diffuser or dimmer.

The higher-wattage units are actually way too bright for many applications. They throw intense light like an arc discharge lamp. They also generate lots of heat and need a substantial heat sink and/or fan cooling. The 50 watt chips heat up like a soldering iron, and will self-destruct in no time if the heat sink is not sufficient.

This holiday weekend, I threw together a 10 watt chip and its driver. I replaced the burnt out dome light in my fullsize GMC truck with it. For now, it is just slapped in there, and it is running without a heat sink. I will be making a heat sink for it that will fit in the hole, hopefully before the chip kills itself. For now, I'm making sure not to leave the door open too long.

For the "pill light replacement" connector/insulator, I chopped off the end of a Bic Stic pen and cut a little slit on each end for the wires to slide into. I drilled a little hole into the center and slipped some speaker wire through it. The whole thing is just hanging by spring tension at the moment. The 10 watt emitter throws WAY more light than the stock incandescent bulb, and actually cost less than a factory replacement mini bulb. The zone has them for 3 bucks each or 2 for 5 bucks. The LED dome lights were 10 bucks each for a lower power, not as bright bulb, and they only had them in "ice white" 6000K color. I put in a "soft white" 3500K chip as I like the "yellowish" light better.

AC_Hacker 12-29-16 09:17 PM


Originally Posted by mejunkhound (Post 52262)
50 watt ebay LED.
Got 10 of these off ebay for 75 cent to $1.12 each, shipping included!

Do you have a link or photo or seller or anything too narrow it down?


jeff5may 12-31-16 02:19 PM

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I posted links to the 10W and smaller variety of stuff I am toying with now. Buying in bulk quantities from China nets you a deep discount. The catch is the items take a month to ship. If I were marketing lights, I would not mind the slow turnaround times in sourcing parts. But I'm making these things for my own personal use. Paying 10 bucks instead of 3 is not a financial stretch, and I get the stuff in 3-5 days. YMMV

These ones are $1.75 each shipped in single or small quantities from China:

10W watts High Power SMD LED Chip Light Beads White Red Blue Yellow Grow Lamp | eBay

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