What LED manufacturers/sellers can even be trusted?

Discussion in 'General Electronics Chat' started by electronice123, Apr 19, 2016.

  1. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    302
    0
    I'm sure this question has been asked here before but I have had no luck finding the answer.

    These days there are many bad LEDs on the market. The sellers convince the consumer their LEDs are high quality by using fake reviews, articles, videos, websites and more. I'm no LED expert so I don't know who to trust or where to go!

    I need (6) white COB LED strips about 6-8" long. I am trying to illuminate a cabinet from all directions to eliminate shadows. The lights will be on for 8-12 hrs/day and need to last a few years if possible.

    For ease of installation I wanted to connect all the LEDs to a common bus (meaning they would all be in parallel) and then use a LED driver.

    Any help would be greatly appreciated to find and source COB LED strips
     
    Last edited: Apr 19, 2016
  2. dl324

    Distinguished Member

    Mar 30, 2015
    3,248
    625
    Pick a manufacturer you like and find an authorized/reputable reseller.

    Products on eBay or Amazon with prices that are too-good-to-believe are good candidates for being counterfeit. I'd be wary of anyone selling many low priced electronic components online. Even if they think they're legitimate, they could be unknowing victims of people selling counterfeit product.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,139
    3,054
    I don't know about strips, but Cree is certainly a respected LED manufacturer. If I had a critical application where the cheap offerings on E-Bay would be too risky, I'd start at Cree.
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    You won't find any in that form factor...
    All the COB LEDS in that size range will be from your typical lower quality Chinese source..

    Cree/Bridgelux/Lumileds/Sharp/Samsung/Citizen all make COB's but in a round form factor.
    You can find "discrete" assemblies (multiple smaller LEDs soldered to a larger PCB) in that size range from quality manufacturers.. But no COB style..
     
  5. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    302
    0
    Awesome,

    Thank you all for those replies. I'll start with Cree, up till now I didn't even know who the good manufacturers were.
     
    Last edited: Apr 19, 2016
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Lets put it this way..
    If you are sourcing your LEDs from Alibaba or similar or even Ebay.. Then you more than likely aren't looking at the good manufacturers..

    If you are in the US then you should check out the offerings from well known electronic distributors like "Digikey, Mouser, Newark".. then Jameco, Future,etc..

    Cree, Phillips, Osram, Seoul, LG.

    Hands down Cree has some of the best discrete/COB,etc.. high power LEDs out there..

    Personally I've used a few high power 50 or 100W LED modules from "China" and had no problems with them except for there is no guarantee you will get the same color spectrum even when ordering 2 of the same LEDs.. My application involved needing to color match 2 large fixtures.. I bought 2 stated as being 10k or something like that and both were quite different.. Still white but not matching..
    Their low cost high power drivers on the other hand are fires waiting to happen (and have happened)
     
  7. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    302
    0
    So I chose a Cree LED which has a forward voltage of 9V and forward current of 400mA.
    The PN is CXA1304-0000-000C00B20E5

    I want to use 3 of those LEDs in series, are my calculations correct for the proper constant current LED driver?

    9V x 3 = 27V so I'll go with a 30-32V driver

    But what about current-I want to operate the LEDs below the forward current, say 350mA to ensure they don't get too hot.....So would I need a 30V ps with 350mA x 3 = 1050mA?
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    No if in series you add the forward voltages but the current is 350mA through the string (it doesn't add)..
    So yes depending on how you want to go you could get a 30+V (48V is pretty common if you can't find anything lower) power supply and use a meanwell LDD-350HW driver
    Or go with an all in one driver like a LPF-16D-42
    One benefit of the LPF is you just need one device and don't have to worry about wiring a power supply and LED driver but you can also add dimming of your fixture with just a simple 100k potentiometer.

    plenty of other to choose from too..
     
  9. DickCappels

    Moderator

    Aug 21, 2008
    2,656
    632
    Besides, many Chinese manufacturers of white LEDs utilize technology covered in American and Japanese patents but are not licensed to do so. That could eventually be a problem if you are planning a commercial product. Small chance of being caught but better to not have to keep looking over one's shoulder.
     
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    What.. say it ain't so.. That would never happen in China ;)
     
  11. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    302
    0
    I figured the current didn't add like you said. I questioned myself as the cob LEDs seem to have their own rules.

    Anyways, the LEDs I chose do not have a voltage or current range, it just specifies the forward voltage is 9v and the forward current 400mA. So, how do I know whether I need a continuous voltage or continuous current ps?

    Also, can I operate below the 400mA, say 350mA to allow the LEDs to run cooler? I'm concerned they may overheat in my cabinet....the cabinet is steel, I planned on mounting the LEDs directly to the cabinet using thermal tape.
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    There aren't that many semiconductor foundaries on the planet - so you could buy from several different 'manufacturers' and find that they all came from the same fabrication plant.

    The biggest problem is counterfeit parts. Organised crime gangs have found that counterfeiting is less jail time than running drugs.

    The gangs usually buy up retired encapsulating equipment, so chances are the fake parts won't have any semiconductor inside. The other trick is stamping any number that sells on reject parts in the appropriate package style.

    Reputable distributors sometimes get caught out by fake parts finding their way into the supply chain - most of those will make good if you end up with fakes. The alternative is buy as cheap as possible direct from China - at least the parts didn't come from Eastern Europe.
     
  13. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    cob rules are no different than any other discrete LED..

    ALL leds need current limiting of some sort.. Some LEDs are an assembly of an LED + a resistor. The resistor is what sets the current the LED will see. With those you simply need a regular power supply (constant voltage)..
    With any high power LED (as far as I know) NONE have build in current limiting so all require a constant current "driver" (power supply).
    The reason that none have resistors is because a resistor is suitable for low current "indicator" LEDs but highly inefficient (they get hot) and does not account for fluxuations in LED forward voltage or supply voltage or whatever..

    You need a constant current supply.. (As stated above you can use a regular power supply + a constant current "module" or an "all-in one" solution that includes both in one package)

    And yes you can always operate below the stated current rating it just won't be as bright.
    If you are just going to mount it to a flat piece of metal then you absolutely need to run it under its rating (more than likely) as a flat plate is a horrible heat sink (far less surface area compared to a real heatsink with fins,etc..)
     
  14. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    If you buy profffesional distributor you often get info where manufactured.

    If you buy eBay, you may get exactly same ic but most likely is made in China and the warehouse lady is not authorized to give qualified reply can't make deals can't test the leds can't change package size or give samples. Because these services are cut the price is low

    Then you have dropshippers which can be problematic. Not all dropship many shop for you from regular district butror
     
  15. electronice123

    Thread Starter Senior Member

    Oct 10, 2008
    302
    0
    Well, Now I'm at a crossroads.....I need to keep my costs down for this project. The LED driver is the biggest cost.

    So, I have been looking at another Mean Well LED driver. This one is a 12V @ 1.67A. The only problem is heat and wiring configuration. I cannot find any 3V LEDs that will give me enough brightness. So, if I used 9V LED's but wired them in parallel could I make the unit safe by installing a series resistor to drop the current to the peak current of a single LED? That way if I used 3 LEDs the current flowing thorugh each of them would be 1/3 their peak?

    But....Would the voltage drop across the series resistor be too high to allow the LEDs to still work?
     
  16. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    I've done some research over the years. I normally use a Booster then leds in series. Gives you several volts adjustment range. You can add a fuse for security.

    Latest lamp I made mobile phone bank Mt3608 Booster and 2x 3w chips with 6 leds each. Flat metal cooler. Doesn't even get warm the leds are good, illuminates the whole room for 8 hours.

    The Mt3608 is 1.2 mhz Booster sot23

    Parallel leds from my research I wouldn't recommend it you need same batch.
     
  17. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Whats your budget and desired lumen output?

    The meanwell LPF + 3 of the Crees is what $30 total... ($40 with shipping maybe)
    The meanwell LDD + power supply + 3 x Cree is around the same..
    But solutions are "cheap" IMO for what you are getting.. and thats components that will last a long time and be very reliable..
    Can you get cheaper.. Sure.. But what are you willing to sacrifice..
     
    electronice123 likes this.
  18. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    I'm actually testing leds I sell

    Don't get the point spending 30x to 50x as much not getting any more or better light. Yet, this testing has costs too, can do better advertising.

    Topic question, get a seller who knows the product best not from a sheet but real world testing.
     
Loading...