99 LEDs....
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Posted by on May 2, 2006, 6:50 pm
Please log in for more thread options Hello! I'm wiring 99 LEDs together and want to power it by battery.... I have a very basic knowledge of circuitry and was wondering if anyone could help me get started? The LEDs that I have are: Kingbright description: L-53HD Forward current max.: 25mA Reverse voltage max.: 5V Wavelength @ peak : 700nm Power dissipation PT: 120mW Light output min.@ 10mA: 2mcd Light output typ.@ 10mA: 5mcd and I have been told that I could power them without a resistor from a 12v power pack. Thanks, any help is greatly appreciated! Alex | |||||||||||||||||||||||||||||||||||||
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Posted by Don Lancaster on May 2, 2006, 7:59 pm
Please log in for more thread options alex_bec@hotmail.com wrote: Are the LED's carrefully factory matched? If not, you do not have a prayer. -- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com Please visit my GURU's LAIR web site at http://www.tinaja.com | |||||||||||||||||||||||||||||||||||||
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Posted by Paul Mathews on May 4, 2006, 11:25 am
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Don Lancaster wrote: > alex_bec@hotmail.com wrote:
> > Hello!
> > > > I'm wiring 99 LEDs together and want to power it by battery.... > > > > I have a very basic knowledge of circuitry and was wondering if anyone > > could help me get started? > > > > The LEDs that I have are: > > > > Kingbright description: L-53HD > > Forward current max.: 25mA > > Reverse voltage max.: 5V > > Wavelength @ peak : 700nm > > Power dissipation PT: 120mW > > Light output min.@ 10mA: 2mcd > > Light output typ.@ 10mA: 5mcd > > > > and I have been told that I could power them without a resistor from a > > 12v power pack. > > > > Thanks, any help is greatly appreciated! > > > > Alex > > >
> Are the LED's carrefully factory matched? > If not, you do not have a prayer. > --
> Many thanks, > > Don Lancaster voice phone: (928)428-4073 This used to be true. However, the resistive component of many high efficiency LEDs is large enough, and their matching is often good enough 'right out of the bag', that parallel combinations work out just fine, particularly if you don't really need brightness matching. It's as if they're self-ballasted to a degree. If the battery pack has some significant amount of source impedance, you can sometimes get away without any resistors. Try it. Paul Mathews | |||||||||||||||||||||||||||||||||||||
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Posted by GregS on May 4, 2006, 11:30 am
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>
>Don Lancaster wrote: >> alex_bec@hotmail.com wrote:
>> > Hello!
>> > >> > I'm wiring 99 LEDs together and want to power it by battery.... >> > >> > I have a very basic knowledge of circuitry and was wondering if anyone >> > could help me get started? >> > >> > The LEDs that I have are: >> > >> > Kingbright description: L-53HD >> > Forward current max.: 25mA >> > Reverse voltage max.: 5V >> > Wavelength @ peak : 700nm >> > Power dissipation PT: 120mW >> > Light output min.@ 10mA: 2mcd >> > Light output typ.@ 10mA: 5mcd >> > >> > and I have been told that I could power them without a resistor from a >> > 12v power pack. >> > >> > Thanks, any help is greatly appreciated! >> > >> > Alex >> > >>
>> Are the LED's carrefully factory matched? >> If not, you do not have a prayer. >
>> --
>> Many thanks, >> >> Don Lancaster voice phone: (928)428-4073 >
>This used to be true. However, the resistive component of many high >efficiency LEDs is large enough, and their matching is often good >enough 'right out of the bag', that parallel combinations work out just >fine, particularly if you don't really need brightness matching. It's >as if they're self-ballasted to a degree. If the battery pack has some >significant amount of source impedance, you can sometimes get away >without any resistors. Try it. >Paul Mathews The 1 watt and 5 watt Phillips Luxeons are very well matched out of the bag. A group of American Bright I used were very well matched. greg | |||||||||||||||||||||||||||||||||||||
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Posted by on May 2, 2006, 8:00 pm
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alex_bec@hotmail.com wrote: > Hello!
> > I'm wiring 99 LEDs together and want to power it by battery.... > > I have a very basic knowledge of circuitry and was wondering if anyone > could help me get started? > > The LEDs that I have are: > > Kingbright description: L-53HD > Forward current max.: 25mA > Reverse voltage max.: 5V > Wavelength @ peak : 700nm > Power dissipation PT: 120mW > Light output min.@ 10mA: 2mcd > Light output typ.@ 10mA: 5mcd > > and I have been told that I could power them without a resistor from a > 12v power pack. http://www.dotlight.de/datasheets/L-53HD.pdf You've had bad advice, as you will be albe to see from the voltage versus current curves in the data sheet. The worst case forward votlage at room temperature at 20mA is 2,5V. 2.25V is typical, so a 12V power pack probably can't drive a string of more than 5V diodes. You could probably set up a current mirror to put a well-defined 10mA through a string of four LEDs running from a 12V supply, but this is a long way short of 99, which you'd have to manange with 25 parallel strings, controlled by 25 current mirrors. -- Bill Sloman, Nijmegen | |||||||||||||||||||||||||||||||||||||
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>
> I'm wiring 99 LEDs together and want to power it by battery....
>
> I have a very basic knowledge of circuitry and was wondering if anyone
> could help me get started?
>
> The LEDs that I have are:
>
> Kingbright description: L-53HD
> Forward current max.: 25mA
> Reverse voltage max.: 5V
> Wavelength @ peak : 700nm
> Power dissipation PT: 120mW
> Light output min.@ 10mA: 2mcd
> Light output typ.@ 10mA: 5mcd
>
> and I have been told that I could power them without a resistor from a
> 12v power pack.
>
> Thanks, any help is greatly appreciated!
>
> Alex
>