Seeking advice on regulators

Discussion in 'The Projects Forum' started by UPIO7, Jul 31, 2012.

  1. UPIO7

    Thread Starter New Member

    Jul 31, 2012
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    Hello! I have been browsing the internet for a while trying to figure this out on my own but I think it's time I ask for some help. I would like to apologize upfront if I missed a previous thread on this exact topic, I saw a few that are related but I still have some questions.

    I am trying to maximize the range of an IR illuminator using the following LEDs-

    10mm Triple chips 200mW IR LED

    • Wavelength : 850nm
    • Vf: 1.4~1.5V
    • Vr: 5V
    • If: 140mA
    • Ipusle: 700mA
    • Power Dissipation:200mW
    • Tjun: 125'C
    • Tsol: 5second @ 260'C
    • MCD=50@ 350mA, MCD=70@400mA
    • Angle: 30' degree

    http://www.lightobject.com/10x-10mm-3-Chips-200mW-Infrared-IR-850nm-LED-30-degree-P91.aspx


    I have looked into linear and switching regulators but this concept is new to me and I could really use some input. My only requirements are the 200mW LEDs and portability. I would prefer to stick to a 9V battery due to its compact size but I am open to alternatives. I am not expecting step by step instructions, but rather for someone to perhaps give a quick summary of the different techniques I could utilize to increase the LED output.

    Also, if anyone has a better idea in terms of the LED itself I would love your input. I have already tried reflectors and using no more than 5 LEDs per 9V.

    Thank You!
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,103
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    For what application, communication? I'm just trying to determine if you need the light, say for illuminating an object, or whether you want the range for sending a signal.

    If it's the latter, you should be modulating the light (flashing it on and off) and filtering that out of the signal at the receiver. That's how remote controls work, and it gives them a much greater range than the brute force, "more power" approach.

    A low duty cycle, high intensity burst is highly visible and saves power, but it won't help for illuminating an object, which requires a high average power.

    A 9V battery is a bit puny for this application, IMHO.
     
  3. UPIO7

    Thread Starter New Member

    Jul 31, 2012
    5
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    Sorry about that, this is for a portable light source so I need to keep it as compact as possible. I currently have to limit the 200mW LEDs to 5 when running off the 9V.
     
  4. UPIO7

    Thread Starter New Member

    Jul 31, 2012
    5
    0
    I know a regulator option would have to account for the video filming and I'm not sure how to go about that.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    Ah, so you want to illuminate for video?

    The high-tech approach would be to flash the IR in synch with the camera "shutter". This means the LEDs could be off most of the time except when a frame is being captured. I assume this is not possible for you, so instead you need continuous illumination.

    There might still be some advantage to a pulsing boost circuit, as long as it's fast enough to not be visible, for instance >1kHz. It won't save energy, but it wouldn't waste much either and could enable using a higher voltage pulse through more LEDs, for instance. It might also provide a way to maintain a constant intensity as the battery sags in voltage, which will be an issue for a 9V battery at your power level.
     
  6. UPIO7

    Thread Starter New Member

    Jul 31, 2012
    5
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    Actually, not so long ago I was considering an IR flash device for photographs so I can always go that route. Would it be a similar concept?
     
  7. wayneh

    Expert

    Sep 9, 2010
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    Similar idea in concept, but at 30 or 60 synchronized frames per second. Not practical unless you could get a synch signal out of the camera.
     
  8. UPIO7

    Thread Starter New Member

    Jul 31, 2012
    5
    0
    Would the joule thief circuit work for this?
     
  9. wayneh

    Expert

    Sep 9, 2010
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    That's what I was alluding to in post #5. But I'm not so sure you'll gain much. The big gain with the typical solar light boost circuit is that it enables you to light an LED with just a single cell. Without the boost, the voltage would not overcome the forward voltage drop of the LED.

    That's not exactly your situation. But you might boost 2 AAs and gain quite a bit more power capacity than a single 9V battery will supply.
     
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