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This light fixture has 3 heads with 15 LEDs for each head. The 3 heads are connected in series. In each head, there are 3 sets of 5 LEDs connected in parallel. The 3 LED sets of 5 for each head are connected in series. For one of the heads, there is one set of 5 LEDs that doesn’t light. When I put a diode tester across each of these 5 LEDs, only one lights up properly, one lights up very dimly, and the others don’t light up at all. There are three of the LEDs that have a small black bump in the middle, so I presume all three of those are burnt out. The light fixture doesn’t start up. When the light switch is turned on, the lights flash twice and then go off. I want to purchase some new LEDs to replace the LEDs with the black bumps, so am requesting some help on how to select the correct ones.

The power supply for this light fixture is made by Eaglerise and is model: ENP021C0700SED1. I was able to get a datasheet for it online, but it doesn’t give any details about the components inside. The 021 in the model number indicates 21W and the 700 indicates 700mA constant current. Here is a picture of the power supply cover:

The heads of the light fixture have aluminum bases. On the back of the bases, it says EGLO 2835-D50-15-6.7W-3000K 700mA DC Constant Current. The heads were evidently manufactured in Austria by a company called EGLO. Their website gives no information about the parts inside their products.
Here is a picture of the back of one of the heads:

Here’s a picture of the front of one of the heads. I drew in red lines for the positive connections, black lines for the negative connections, and two blue lines to connect the parallel arrays together. Here’s a picture of the front of one of the heads.  I drew in red lines for the positive connections, black lines for the negative connections, and two blue lines to connect the parallel arrays together.

The datasheet says that the power supply operates from 500mA to 700mA. On the cover it says 700mA constant current.

The datasheet says that the power supply has overvoltage protection set at 48V, yet the cover says maximum 38V.

I made some current and voltage calculations. I’m not familiar with how the LEDs respond with regard to even voltages and load sharing. I would think that the LEDs would be designed to be matched close enough to have same voltages for a given amount of current and to have equal load sharing. In my calculations, I presume voltages across the LEDs to be the same and load sharing to be equal.

Here are my calculations for 700mA current: 700mA through each head (the 3 heads are in series with each other). 700mA through each set of 5 parallel LEDs (each head has 3 sets of 5 parallel LEDs). 700mA divided by 5 = 140ma through each LED.

Here are my calculations for voltages if output of power supply measures 20V: 20V divided by 3 = 6.7V across each head. 6.7V divided by 3 = 2.2V across each LED.

Here are my calculations for voltages if output of power supply measures 30V: 30V divided by 3 = 10V across each head. 10V divided by 3 = 3.3V across each LED.

Here are my calculations for voltages if output is 38V: 38V divided by 3 = 12.7V. 12.7V divided by 3 = 4.2V across each LED.

Here are my calculations for voltages if output is 48V: 48V divided by 3 = 16V. 16V divided by 3 = 5.3V across each LED.

Calculations Table

So finally, my question is: What are the parameters that the LEDs should have?

Update: I ordered LEDs. Instead of ordering ones that are 3000K, I ordered 5700K, from mouser. The rated forward voltage of the new LEDs is 2.86V, forward current is 150mA, and the power rating is 500mW. The light is working now. I have all the LEDs replaced on the first head and plan also to do the other 2 heads when I get time. I made a schematic showing the configuration of the LEDs and made up a chart with measurements that I took. The New LEDs also have a 120 degree viewing angle, luminous flux is 75lm, CRI is 80, and the lens transparency is diffused. I still don't know whether the diffused lens or the clear lens is better. In one web page that I read, it said the diffused lens helps to scatter the light which is better for a wider viewing angle, however the LEDs at Mouser are 120 degree viewing angle for both the clear and the diffused lenses.

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    \$\begingroup\$ The power supply describes the properties the LEDs must have: forward voltages sum to between 20 and 30V at a current of 700mA. That is it. You can use one 25V LED module rated for 700mA, 8 3V modules rated for 700 mA in series, or any series/parallel combination summing to that. \$\endgroup\$ Commented Oct 6, 2022 at 0:22
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    \$\begingroup\$ White LED is usually UV covered with luminophor. So the drop voltage should be 3-3.2V. They all pretty much the same, so your choise should be based on current. \$\endgroup\$
    – user263983
    Commented Oct 6, 2022 at 1:44
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    \$\begingroup\$ @user263983 Blue, not UV. Look at the spectral output of almost any white LED and you'll see the blue peak. \$\endgroup\$
    – Kyle B
    Commented Oct 6, 2022 at 5:24
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    \$\begingroup\$ @user263983 Do you have any source for your claim "White LED is usually UV covered with luminophor" ? \$\endgroup\$
    – Uwe
    Commented Oct 6, 2022 at 6:02
  • \$\begingroup\$ I want my light to have as much brightness as possible and light up the entire bathroom. Is it better to use LEDs with diffused transparency or clear transparency? Should I be using LEDs that are rated at 500mW and 150mA? \$\endgroup\$
    – ednja
    Commented Oct 6, 2022 at 19:41

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I didn't really get the answer I was looking for. I was looking for the best LED parameters for my application. I ended up deciding on my own and it worked out. I used to work for mnufacturers of switch-mode power supplies and repaired a lot of them. It's been many years though since I did that and I'm retired now. I wasn't sure about how LEDs behave with a constant current supply, but now I know.

I made up a schematic for this light and a chart with voltage and current readings at three different stages of my repair. These measurements tell a lot about how they behave. Unfortunately, StackExchange isn't allowing me to upload any more pictures.

The LEDs that I chose have these parameters:

Mouser Part #: 941-JE2835BWTNH57GAN

Brand name and type: Cree 2835

Illumination Color: Cool White

Color Temperature: 5700K

Luminous Flux: 75 lm

Color Rendering Index (CRI): 80

Viewing Angle: 120 deg

Forward Current: 150mA

Forward Voltage: 2.86V

Power Rating: 500mW

Lens Color: Tinted

Lens Transparency: Diffused

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