[sdiy] SMD LED intensity and lenses

[Rutger Vlek]

@John: yes, PWM would have been nice, but this is an entirely analog design, without a microcontroller.

@Mike: thanks. Initially, I matched several colors of LEDs together for the LED ring that had similarly spec'ed intensities (in lumen). However, upon testing I found these values weren't comparable at all. Then I discovered Kingbright spec two values, one according to some weird magical standard, and one according to an ISO norm. The latter gave me hope intensities would become comparable, and now I'm deciding on which LEDs to order. I have a subset of options that include both dome and flat lenses, and I'm wondering if it is a problem to get a mixture of these into the led ring. I'll install a current limiting resistor per color in the led ring (consisting of roughly 5 green, 4 orange, 3 red, 2 blue LEDs), so I can later even out the brightnesses between colors by adjusting the resistor.

Best,

Rutger


On 24 mei 2017, at 16:56, Mike HEQX wrote:

> In that case there wont be much dispersion and absorption, which is what can even out the intensity variations.
> 
> Are you having trouble between colors or between colors and parts as well?
> 
> Variations in color intensity can be solved, but if the components are also not matched well that is more difficult.
> 
> You might consider a diffuser disc of thin white or translucent material ( like Mylar or Acrylic ) to place over the led ring under the light pipes. You can also apply a color filter in this way.
> 
> Mike
> 
> 
> On 5/24/2017 10:43 AM, Rutger Vlek wrote:
>> Hi Mike,
>> 
>> The light pipes are transparent with a flat 3mm diameter surface on the panel side.
>> 
>> Rutger
>> 
>> 
>> On 24 mei 2017, at 15:55, Mike HEQX wrote:
>> 
>>> Are your light pipes white, transparent, or translucent?
>>> 
>>> Do they have a flat or spherical light gathering surface?
>>> 
>>> 
>>> 
>>> On 5/24/2017 2:52 AM, Rutger Vlek wrote:
>>>> Hi guys/girls,
>>>> 
>>>> I'm finishing up a new product that will contain a multi-color LED ring, which I plan to do with SMD leds in 4 different colors. In the prototype I had a hard time getting the intensities of the various colors of LEDs to match. I've now learned that not all manufacturers spec according to a comparable norm, so I've decided to stick with Kingbright components that at least have a reference to a uniform norm in their datasheets to make their reported intensities more or less comparable between colors and between leds. I can design in an option to regulate supply current to various colors individually, so technically I can compensate for any differences in intensity between leds.
>>>> 
>>>> However, now I'm considering which leds to start with and have options for 0603 leds with a dome lens or flat lens. There will be lightpipes in front of the leds to bring light to the front panel, so is there any advantage or disadvantage to the type of lens? And more importantly, will I run into issues if I combine leds with a dome lens from one color (and spec'd brightness) with other types of lenses? I suspect the lightpipes will straighten out a big portion of the leds angle of dispersion, but I'm still hesitant to mix and match, as I feel the resulting brightness at the end of the lightpipe may vary.
>>>> 
>>>> Any suggestions?
>>>> 
>>>> Regards,
>>>> 
>>>> Rutger
>>>> 
>>>> ps. LED rings are cool, as are bow ties.
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