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Looking for Higher powered UV LEDs

Discussion in 'LEDs and Optoelectronics' started by sergioq, Jul 30, 2014.

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  1. sergioq

    sergioq

    15
    0
    Oct 29, 2013
    Hello all,

    Am looking for higher powered UV LEDs. Trying to make a simpler currency strip viewer. The specs for what I am using now are below****. It's a cheap LED, but it works.

    My questions are:

    * Are there higher powered (radiant wise) LEDs that wouldn't require a car battery to light them up?
    * Do multiple LEDs mean a brighter output when it comes to UV?

    Obviously there are $100 UV LEDs out there, but if there can be an $18 UV flashlight, there must be some solution to what I wish to do.

    Any thoughts would be greatly appreciated as this is new to me.

    Thanks ahead,

    Sergio

    ****
    ColorUV (Blacklight)Continuous Forward Current30
    Forward Voltage3.5VLED Package5 mm (T-1 3/4)
    Lens ColorClearMaximum Forward Voltage4V
    MillicandelaN/AOperating Temperature-40~+85 °C
    Peak Forward Current100mAPower Dissapation120mW
    Radiant Power30mWReverse Current10µA
    Reverse Voltage5VStorage Temperature-40~+100 °C
    Total Power Consumption0.105 WattsTube DiameterT1-3/4
    Viewing Angle15 degreeWavelength380 nm
     
  2. shumifan50

    shumifan50

    556
    56
    Jan 16, 2014
    You can make the LED a lot brighter by over-driving it in short bursts as used in remote controls. So instead of a current of 30ma continuous, you put 100ma through it for x% on and 100-x% off, where x will be determined by the LED's time taken to dump the heat generated. The current you can put through your example is 100ma, so leaving some headroom would be wise(80ma).
     
  3. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    You can use a small array of the cheaper LEDs.

    It's your choice to use a car battery or not... ;)
    When you connect them in series (daisy chaining them together) you will need a resistor for each string, and the required voltage must be higher then the voltage of all of the LEDs in the string added together. (35-40V... but only 30mA for 10 LEDs)
    When you connect them in parallel (tying all the negative side together for example) you will need a resistor for each 'branch' or LED. You can keep the voltage low, but the current required will go up. (ie. 300mA for 10 LEDs, but only about 3.5-4V)
    You can mix and match this method, and you will find some more resources on driving more LEDs here: https://www.electronicspoint.com/resources/got-a-question-about-driving-leds.5/


    Would this require PWM? or would you suggest something like a oneshot?
    http://www.instructables.com/id/Make-an-LED-Blaster/step2/Build-the-555-ic-one-shot-timer/
     
  4. shumifan50

    shumifan50

    556
    56
    Jan 16, 2014
    This is essentially just a square wave with a fixed duty cycle of x%, mostly done with 555 timer. Using this trick you can get a range of more than 10m with IR leds whereas the normal range would be much less than 1m.
     
    Last edited: Jul 31, 2014
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
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    Jan 21, 2010
    I have a colleague making a UV LED device for exposing PCBs. He reported that with just one LED the required exposure times were comparable to his multiple fluorescent tube device, albeit with some drop off at the edges. He's planning to place 10 to 15 of these LEDs in a hexagonal pattern, and is expecting to be able to achieve quite small exposure times even through paper "negatives".

    Would you like me to enquire what LEDs he's using?
     
  6. sergioq

    sergioq

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    0
    Oct 29, 2013
    Wow....all this went over my head. I feel so stupid.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Heh. Don't worry. I'll find out what my colleague is using. That way we can tell if the light ouput of yours is low or if it's something else.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
    2,830
    Jan 21, 2010
    OK, these are what my colleague bought (the 3W versions). http://www.ebay.com/itm/321340939953

    He says the radiant intensity from 120mm away is similar to his 4 x UV fluro tube exposure box. The ratings are as follows:


    Emitting Colour: UV
    DC Forward Voltage: 3.9V - 4.5V
    DC Forward Current: 700mA
    Luminous Intensity: 50~55mW
    Wave Length: 365nm - 370nm
    Viewing Angle: 120 Degree

    Note that the wide viewing angle means they will cast light over a much wider area even when you're close up to them.

    You would have to use a constant current source and heatsink them. one might be sufficient for your needs.

    For use a few seconds at a time, you could run it from batteries.
     
  9. shumifan50

    shumifan50

    556
    56
    Jan 16, 2014
    One thing to bear in mind is that looking at such a powerful UV source will damage your eyes, so the unit must be designed in a fashion such that it is not possible to look directly at the UV source or its reflection.
     
    (*steve*) likes this.
  10. sergioq

    sergioq

    15
    0
    Oct 29, 2013
    My original question is here, Looking for Higher powered UV LEDs ...link is here:

    https://www.electronicspoint.com/threads/looking-for-higher-powered-uv-leds.269615/

    So my question is, as a total newcomer to this area, can I amplify my inexpensive UV LEDs? Do mirrors help? Do lining up 5 in a row (with proper) current make them more useful?

    Yes...the ones I have help view currency threads (but dimly).

    Any thoughts would be appreciated.

    Many thanks again,

    Sergio
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,482
    2,830
    Jan 21, 2010
    Yes, you will multiply your light output if you use multiple LEDs (correctly). So 2 LEDs will have twice the light output of 1. 5 will have 5 times the light output, etc.

    The best options might be a higher power LED or one with a narrower half-angle. Mirrors may not make a significant difference since the light is usually concentrated in one direction already (the half-angle tells you how strong this effect is)
     
  12. sergioq

    sergioq

    15
    0
    Oct 29, 2013
    I have some 5v UV LEDs that are of proper wavelength to see the currency strips in US money. Am having a problem with brightness however.

    So I thought I might ask a different question?

    Are there (inexpensive enough) blacklight LEDs that will view the currency strips in money (wavelength wise), yet without the harm of UV LEDS?

    Many thanks ahead, as always.

    Sergio
     
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    It's the same question.

    You need brighter LEDs, or to run them at higher current, or to reduce the ambient lighting.
     
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