I am at my wits end I built a Blue LED spot light using as per the attaché diagram.

I ran a 24 volt supply to a regulator which dropped the voltage from 24 to 13.9 volts It is a 6 amp supply @13.9 Volts regulator.

for 3 days solid the light was on and then for no reason that I know the LED's stopped working

PLEASE can some one lell me what I am doing wrong!

 

Your circuit seems sound, just did a few calculations which I'm sure you did to arrive at that resistor value

Have you tested the LEDs individually out of circuit? have you done the standard fault finding test: check the input and check the output and see if it's what you expect. The input in this case may be your 24V or 13.9V regulated voltage, the output would be the voltage accross each LED.

 

Yes, a few minutes with a voltmeter will reveal the problem. Probably blew a fuse?

 

Do you know how are the V/I of LED?

Assuming that the V_LED = 3V.
3v x 4 = 12V
13.9V - 12V = 1.9V
I = 1.9V/47Ω=40mA.

If the V_LED = 12V, V_R = 24V - 12V = 12V.
The R should be like this:
R =12V/40mA = 300 Ω
If using 80% of 40mA = 32mA
Then R=12V/32mA=375Ω, you may using 390Ω.
If V_LED isn't not 3V, then you can calculate the value as above.

 

Thank you for all the help. I will check and report back my findings

 

It's unlikely the LEDs are the problem. Start at the wall socket and work towards the LEDs, not the other way around.

 

If you haven't got a heat sink on the regulator, I would think that is where the problem is. You're dropping lots of voltage across it, and that goes in heat loss (power dissipation)

HTH Steve

 

just ditch the regulator..and recalculate the resistors for 24V..
more in each series string will help with resistor wattage..

 

+1 @ mcgyvr Clearly a more simple solution!

 

330 ohms, 1/2 watt, for (5) 3.2V LEDs and 24 volts to produce 24.2 ma.

 

Have 2 Chains of 8 LEDs and a very small resistor. Generate less heat

Ramesh

 

Have 2 Chains of 8 LEDs and a very small resistor. Generate less heat Ramesh

Two chains of 8 LEDs does not make 20 LEDs.
8 LEDs times 3.2 volts is more than the 24 volts available.