Author Topic: Can somebody identify this LED?  (Read 1115 times)

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Offline 6PTsocket

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Can somebody identify this LED?
« on: October 09, 2018, 01:03:30 am »
This came out of the light fixture in the freezer of my fridge. It was very intermittent. I foolishly replaced the switch without checking it first because Kitchenaid/Whirlpool light switches often fail. I would take it out put it back and it would work for a little while. I finally figured out that the problem was thermal; after it got cold it would quit. I figured it needed to be resoldered but but there is nothing visible on the edges. I assume it is soldered on the back and was hot air soldered into place. Anyway I accidently blew it. The best price for the whole fixture is over 40 bucks on ebay. The appliance dealers get more like 65. If I can ID this led and how much light it puts out, I can probably substitute one with nomal SMD side terminals. It measures 3mm square and is probably around 1mm high. Does this look familiar to anyone? Thanks.To be honest, I have not combed through Mouser or Digikey yet. Maybe some led supplier is a better source of info.?

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Online james_s

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Re: Can somebody identify this LED?
« Reply #1 on: October 09, 2018, 01:08:24 am »
Any idea what the driver puts out? You can probably get any number of LEDs that will work for a few bucks off eBay or dealextreme. Worst case you could get an LED and driver or one of those mains voltage COB modules that has a built in driver. It's not like the light in a fridge runs much so even a cheap one should last many years.
 

Online tooki

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Re: Can somebody identify this LED?
« Reply #2 on: October 09, 2018, 01:22:46 am »
If your measurement is accurate then it’s probably a 3030 LED. (Thats 3.0x3.0mm. 2835, 3528 and 3535 also exist, among many other SMD LED sizes.)

But seriously, this isn’t a super critical application, look on eBay, there are tons and tons of both LEDs and LED modules that you could solder in place of that.
 

Offline Brumby

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Re: Can somebody identify this LED?
« Reply #3 on: October 09, 2018, 01:48:52 am »
My first thought was a 3030 also - but looking at that mounting area, it seems you could put a 5050 in there without a worry, so I don't think physical size is going to be a problem.

The two things that would be useful to know is the Vf and the current.  Just checking Mouser, you can get LEDs that range from 2.95V to 6.3V and currents that range from 65mA to 400mA. The brightness ranges from 25lm to 156lm, so you could cut down on the range of interest by working out what brightness you would want - and the colour.  Even then, you would have to do some homework or take a guess at the voltage/current - because you have LEDs of similar brightness that will take different voltage & current combinations.  For example, around the 150 lm mark you can get one LED that runs at 3.2V 400mA and another at 6V 200mA.

If it were me, I would look at what brightness I would need, filter on the colour temperature and probably get a 6V one (or thereabouts) and a 3V one (or thereabouts).  I would try the 6V one first and if that worked as well as the original, then I'd call it a win.  If it was too dim, I'd then try the 3V one.

Having some real voltage and current figures would be nice, though.
 

Offline 6PTsocket

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Re: Can somebody identify this LED?
« Reply #4 on: October 09, 2018, 02:55:47 am »
My first thought was a 3030 also - but looking at that mounting area, it seems you could put a 5050 in there without a worry, so I don't think physical size is going to be a problem.

The two things that would be useful to know is the Vf and the current.  Just checking Mouser, you can get LEDs that range from 2.95V to 6.3V and currents that range from 65mA to 400mA. The brightness ranges from 25lm to 156lm, so you could cut down on the range of interest by working out what brightness you would want - and the colour.  Even then, you would have to do some homework or take a guess at the voltage/current - because you have LEDs of similar brightness that will take different voltage & current combinations.  For example, around the 150 lm mark you can get one LED that runs at 3.2V 400mA and another at 6V 200mA.

If it were me, I would look at what brightness I would need, filter on the colour temperature and probably get a 6V one (or thereabouts) and a 3V one (or thereabouts).  I would try the 6V one first and if that worked as well as the original, then I'd call it a win.  If it was too dim, I'd then try the 3V one.

Having some real voltage and current figures would be nice, though.
That's the problem. I earlier applied around 3 volts and it lit. When I had it plugged in and it was not lit, I measured 12.58 volts across the wires. I assumed there must be a current limiting resistor in the board. It clearly is elsewhere and I was reading open circuit voltage. I took it out and hit it with 12 volts and POOF. My bad. I have no way to tell how much current it pulled. I should have measured it when it was working. I am well aware how leds are current devices. I was hoping that the physical size of 3mm x 3mm would get me in the ball park as to what is available in that exact size. 

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Online james_s

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Re: Can somebody identify this LED?
« Reply #5 on: October 09, 2018, 04:36:17 am »
The current limiting is almost certainly in the driver. Power LEDs don't use a resistor to limit the current, it would waste far too much power. If you get 12V open circuit from the driver then try a 6V LED.
 

Offline Brumby

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Re: Can somebody identify this LED?
« Reply #6 on: October 09, 2018, 07:35:32 am »
Ok - open circuit voltage is 12.58V, so let's try a first year exercise...

Get a 1W resistor - say 39R - and measure its actual value.  Then bridge it across the (now blown) LED.  Measure the voltage across the resistor.  You can now work out the equivalent series resistor for the supplied power.

To check, try something like a 56R resistor and repeat.

If the LED is being fed by a fixed voltage and current limiting resistor, then the ESR calculations of each of the above exercises will be the same.  However, if the LED is fed by a constant current source, then the current flowing through each resistor will be the same.
 

Offline 6PTsocket

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Re: Can somebody identify this LED?
« Reply #7 on: October 09, 2018, 04:33:47 pm »
Ok - open circuit voltage is 12.58V, so let's try a first year exercise...

Get a 1W resistor - say 39R - and measure its actual value.  Then bridge it across the (now blown) LED.  Measure the voltage across the resistor.  You can now work out the equivalent series resistor for the supplied power.

To check, try something like a 56R resistor and repeat.

If the LED is being fed by a fixed voltage and current limiting resistor, then the ESR calculations of each of the above exercises will be the same.  However, if the LED is fed by a constant current source, then the current flowing through each resistor will be the same.
Sounds good.  I was looking at 3030's and the range is wide. The data sheet for the 6 volt ones shows a symbol indicating it is actually 2 led's in series. There are other led fixtures in the fridge, 5 on the headliner and 2 on each side but they look a bit different. The 4 on the sides are a also out but I will deal with them later. At 3 volts each, they could be in series.

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Online james_s

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Re: Can somebody identify this LED?
« Reply #8 on: October 10, 2018, 04:11:58 am »
The voltage of individual LED chips doesn't vary much, so a 6V LED will be two chips in series.

It's probably not very critical at all, as long as the LED is even remotely close it will likely work fine.
 


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