Electronic converters

Discussion in 'General Electronics Chat' started by boatsman, Mar 6, 2015.

  1. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    I have a number of electronic converters input 230VAC 50Hz 0.26A, output 11 .5 V 60W max (10 -60W) that were used to power 50W halogen lamps. Can I use these converters with some sort of rectification to power simple low voltage LEDs?
     
  2. #12

    Expert

    Nov 30, 2010
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    yes. Please describe them better. They might already be DC.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Take pictures of the inside..
     
  4. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Sorry, didn't notice it when I sent specifications; the secondary output is listed at 11.5 VAC
     
  5. takao21203

    Distinguished Member

    Apr 28, 2012
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    I dont recommend it.

    -Not short circuit proof
    -Not current limited as such (for instance when there is a surge). Current limited means either through active regulation, or by design (inductor which has certain DC and ESR so doesnt burn the LEDs)
    -Not meant to be for rectification or operation without load (tough this should be possible).

    If you make a small short, these cheap Halogen converters will burn out and its not worth fixing them.

    Yes you can drive LEDs with electronic power supplies- for instance a laptop brick typically has overcurrent protection.
    The art is to load it with LEDs so they get slightly less than full current, and prevent runaway if they overheat for some reason.
    It is doable. You can stepup voltage, and with 60V you have a range of a few volts.

    But for a realworld installation, you need to monitor the temperature and shutdown if the LEDs get too hot.
    You cant just rely on the cooling fans spinning forever.

    Unless you are ambitioned, using regular LED driver modules is the easiest way.

    I have driven smaller LEDs just with a MC34063, and used a surprisingly short piece of wire as the "resistor" for the current sense.
    First I used a longer piece, but I couldnt get appropiate brightness.

    It is proper since it is a real current sense, actually limiting the current.

    Back to the Halogen transformers, I really dont recommend it, they dont have a protection like laptop bricks, which either shutdown or "blink".
    If your LEDs run away, the module burns out, or it doesnt burn early enough, and your LEDs do.
    If you only drive smaller LEDs then its the same problem when driving with a voltage source.

    Its doable, but has some risks. You have less than one volt with smaller voltages, and you need to monitor temperature.
    Then you could as well monitor current, or just dont care. But that never works for a professional installation.

    When you use a stepup converter + laptop brick, you have two protections basically:

    -Laptop brick overcurrent protection
    -Design limit of the stepup converter (it can only crank out certain current especially when you hack it for higher voltage).

    OK you can connect a large array of LEDs to a toroid transformer- if you dimension it right.
    Voltage will break down with higher current. But its difficult, and fails if too many LEDs burn or are disconnected.
    You almost need to drive the toroid at the margin of overloading it + cool it as well.

    I had more than 500 Watts LEDs at some stage, a big mess of wires, then got rid all of it.

    Now I use a small 60W ready made LED lamp, very heavy metal floodlight case,
    very satisfied with it.

    About $1/Watt.
     
  6. #12

    Expert

    Nov 30, 2010
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    Yes, you can add a rectifier and a capacitor, then run lots of little LEDs with resistors to keep them safe, or even some medium size LEDs if you are careful to give them cooling fins. I did not see where you said you wanted to run LEDs without building a proper current limiter, so that doesn't seem to be a problem.
     
    Roderick Young likes this.
  7. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    As described the 'converters' (FE core transformers?) exhibit a safe working current of 4A+ --- Construction of a regulated PS may be worth your while...

    Following the bridge & filter you could keep things simple via use of 'plain vanilla' 3-terminal linear regulators (78xx series are as simple as it gets).

    That said, to realize full utilization of the transformer's current capability (in addition to real over-current protection [foldback] and Eout flexibility) I suggest the LM138K series... One caveat, however, be mindful of the 'safe area' power dissipation as regards 'Ein-Eout'*Iout characteristic (failing which, instead of a regulated PS, operation will be on a par with that of a 'power relaxation oscillator' ;))

    Note that while the LM317K is similar it exhibits notably less current handling capability and, IMO, much less 'ruggedness'

    Best regards
    HP
     
    Last edited: Mar 6, 2015
  8. #12

    Expert

    Nov 30, 2010
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    Actually, LEDs are simple enough that they don't need a filter capacitor and several 3 pin regulator chips will run on mere pulses. Get more pacific about your desires and we can steer you in the right direction.
     
  9. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Perhaps I overreached --- Indeed, if all you wish to do is operate LEDs there is no need for the 'complexities' described in my previous post -- I was merely thinking that, should you be 'bitten by the electronics bug', a basic regulated PS is fundamental to further pursuit... :)

    Best Regards
    HP
     
  10. boatsman

    Thread Starter Senior Member

    Jan 17, 2008
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    Thank you all for replying. I have a number of LED clusters (from LED headlamps that fits over the head, not the vehicle type) that are powered by 3 x AAA batteries. I have successfully powered such clusters with an ordinary plug in power supply of 4.5VDC at 350mA. I want to power these clusters with the converters and use as many clusters as possible with each converter.
     
  11. wayneh

    Expert

    Sep 9, 2010
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    You can, but there are folks (your friends and family?) that could use these as-is since halogen lamps are still quite common. I could use a few of these myself. The halogen lighting kits they sell include lots of lamp but usually only one adapter.
     
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