What is an appropriate power suppl

Discussion in 'General Electronics Chat' started by dvan, Feb 8, 2014.

  1. dvan

    Thread Starter Member

    Feb 8, 2014
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    1pc 10W 10 Watt blue High Power LED beads Light Lamp Chip 45mil 460-475NM

    1.Chip size:45X45 MIL

    2.Forward Voltage: 9-12V

    3.Forward Current 900ma-1050ma

    4.Luminous flux: 300-400LM

    5.Output power: 10W
    thats all i have what else do i need for circuit what power supply should i use thanks
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    I am going to try to translate:
    * Number of LED: 1
    * Forward voltage of the LED is 9-12 V
    * Current for the LED 900-1050 mA

    Does your country have 110 V AC or 220 V AC?
     
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  3. ian field

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    Oct 27, 2012
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    12V SMPSU boards were relatively unusual - +5 & +12 supplies were readily available on the surplus & salvage market, but you have to load the 5V rail to get anything from the 12V one.

    With the simpler designs using a TL431 to drive the feedback optocoupler, it was a simple enough matter to recalculate the voltage sensing resistors and move the top of the resistor network from the +5 to the +12.
     
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  4. dvan

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    Feb 8, 2014
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    im in the us. so 110
     
  5. dvan

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    Feb 8, 2014
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    i havent a clue what you just said man sorry.
     
  6. shteii01

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    The one on the far right is what you want. But. It looks like it is dual power supply, 5 V and 12 V DC, it might need a load connected to 5 V to get the 12 V working.

    The one of the far left might work.

    The one in the middle outputs AC, so it is AC to AC converter, it is not going to work because you need DC.

    If they use the psu on the far right and it works. It outputs 1500 mA. Would they need liming resistor?
     
    Last edited: Feb 8, 2014
  7. ronv

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    Nov 12, 2008
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    Yes, it needs a series resistor with the supply on the right. Try a 5 ohm 5 or 10 watt resistor. If the current is to low (not as bright as it should be) use a lower value. The LED also needs a heat sink so bolt it to something metal to get rid of the heat.
     
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  8. takao21203

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    Apr 28, 2012
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    attach it to a VGA cooler with silicon compound (No more nails).

    Use a buck converter from eBay with a 10 turns adjuster, and carefully crank it up. Measure the current when the LED is hot so it is appropiate.

    If you want to go safe, only use 0.7x the max. current
     
  9. mcgyvr

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    Oct 15, 2009
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    none of those supplies are "right"
    High power LED's require "constant current" power supplies.. Those are all "constant voltage"..

    I would buy a meanwell LPF-16D-15 and a 100k potentiometer. The pot will allow "dimming".. If you don't want dimming then I would just use a 80k resistor across the dimming inputs just to reduce the output current slightly.

    And make sure you mount that LED to a suitable heatsink or it will just burn up on you..
     
  10. dvan

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    Feb 8, 2014
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    i pulled two heat sinks out of an old tube tv. i was wondering can i use gorilla glue to stick them together ?

    also regarding the 12v & 5 v supply i tested the wires and the yellow is running at 11.85 volts
     
  11. mcgyvr

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    The bottom heatsink is fine for a 10W led..

    again those power supplies won't work. The LPF and 100K pot is the "proper" stuff to buy..
     
  12. ian field

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    Oct 27, 2012
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    As long as you have sufficient voltage headroom, a current limiting resistor is usually good enough. As long as the supply voltage is regulated constant, the only cause of drifting current value is the small (ish) change in LED Vf with temperature.

    Of course, the more headroom you accommodate with a higher resistor - the more power you waste as heat.
     
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  13. dvan

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    Feb 8, 2014
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    thanks for your knowledge. i guess some people dont understand this is a low budget project.. anyhow what resistor should i get ? does a resistor limit voltage and amperage ?
    power supply is 12v 1.5 am
    led is 9-12 v 900-1050 milliamps
     
  14. shteii01

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    Feb 19, 2010
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    ronv here: http://forum.allaboutcircuits.com/showpost.php?p=695597&postcount=7
    suggested 5 Ohm, 5 Watt or 10 Watt resistor.
     
  15. ian field

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    A resistor drops a certain voltage when you pass a certain current through it depending on the resistance.

    There are some good Ohms law tutorials online, also some LED tutorials on how to calculate the dropper resistor.

    You need to add up however many LED Vf drops there are in series and subtract this value from the regulated supply voltage, the remaining voltage is dropped across the resistor, using Ohms law you can calculate the resistance to pass the required current at that volt drop - go for the next higher preferred value resistor, you need to allow for Vf reducing with increase of LED temperature.
     
  16. mcgyvr

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    Oct 15, 2009
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    Using a fixed resistor and looking at the possible forward voltage drops of the LED the current changes considerably.
    12V supply..
    If R = 5 ohm
    if Vf = 9
    12-9Vf=3/5= .6A (running at 60% of what its rated for)
    or
    if Vf = 11
    12-11vf = 1/5 = .2A (running at only 20% of what its rated for)

    If thats ok with you then go right ahead..
     
  17. dvan

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    Feb 8, 2014
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    im probably annoying you now.. i dont know why it has to be 5 ohm. im researching all over youtube but this is so much information..
     
  18. ronv

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    It's ohms law. R=E/I. Resistor = voltage / current.
    From your specs the LED drops a voltage of 9 to 12 volts at .9 to 1.05 amps.
    So if you get an LED that drops 9 volts and you have a 12 volt supply there will be 3 volts across the resistor. So using ohms law I=E/R or 3/5=.6amps. This means that the LED will have about 60% of its maximum light if you get one with 9 volt drop. So it is safe to run at .6 amps (less than 1.05 amps). Now if you get an LED that drops more voltage there will be less across the resistor so the current and the light will go down, but fortunately one of the characteristics of LEDs is that the voltage drop goes down as the current goes down so it will most likely work ok. You could of course use a 3 ohm resistor then the maximum current would be 1 amp.
    To calculate the power of the resistor you can use P=IE. So .6X5 or 3 watts. You want to make it at least 2X that as it will be smoking hot at it's maximum rating.
     
  19. dvan

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    Feb 8, 2014
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    So if I want to optimize I have to get a 100k pot?
     
  20. shteii01

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    Feb 19, 2010
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    Eh?

    We are talking 3 Ohm, 5 Ohm. 100 kOhm pot is 100,000 Ohm!!!!
     
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