# 12 x 5mm LED light fails ?

Discussion in 'The Projects Forum' started by RodneyB, Feb 21, 2015.

1. ### RodneyB Thread Starter Active Member

Apr 28, 2012
643
13
Well I am at my wits end.
I have been trying to Sort out a system so that I have some quality of life whilst we have these 15 hour daily power cuts.
I made up some LED lights with LED's I imported. (Attached Datasheet)
I used the following on line LED calculator to design the layout and work out the resistors (Only cause I don't know how to make the correct driver)
I made the resistors bigger as I want the LED's to last.
Measuring the current at 12 Volts using my mason power meter it reads 0.06 Amps, 0.7 Watts. I assumed this would be ok.
Well 90% of them have failed within a month. Before I make a fool of myself and blame the LED's I want to understand if this is the problem OR the calculator OR me.

2. ### RodneyB Thread Starter Active Member

Apr 28, 2012
643
13
Sorry Left out the attachment

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33
3. ### #12 Expert

Nov 30, 2010
16,663
7,307
It looks right.
15 ma per series string, the right amount of voltage across the resistor...
I'm coming around to blaming the LEDs.

Apr 5, 2008
15,796
2,384
Hello,

Do you have the datasheet of the leds?

Bertus

5. ### RodneyB Thread Starter Active Member

Apr 28, 2012
643
13
To many failed I just wanted to be sure! Here

6. ### RodneyB Thread Starter Active Member

Apr 28, 2012
643
13
Sorry to many failed so I thought it best to get advice, Here is the datasheet

• ###### 5mm white led.pdf
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Apr 5, 2008
15,796
2,384
Hello,

The datasheets tells me that the absolute constant current is 20 mA.
With the 150 Ohms resistor and the lowest voltage given in the datasheet ( 3.0 Volts), you will be at this 20 mA.
Raise the value of the resistor to 180 or even 220 Ohms to be safe.

Bertus

8. ### RodneyB Thread Starter Active Member

Apr 28, 2012
643
13
Hi

Thanks very much, I will change it and give it a test. Thank you for your help

Rod

9. ### #12 Expert

Nov 30, 2010
16,663
7,307
But RodneyB measured 60 ma for 4 strings in parallel.