# about led brightness and angle

Discussion in 'LEDs and Optoelectronics' started by alper, Feb 4, 2017.

1. ### alper

9
0
Aug 5, 2016
Hi guys i want to build an exprosure box for pcb and i am planing to use a 365nm led with 120 wieving angle and the brightness is not on the website so i dont know about it but can you guys tell me please how can i calculate the led light on the surface. Like how many centimeters between leds or how many centimetrs should i put between the leds and the glass/surface?

p.s sorry about my english. it is not my natuve language

Thank you

2. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
A colleague of mine is building an exposure box using LEDs. I recommended a hexagonal arrangement of LEDs but he found a regular matrix provided better illumination at the corners.

Whatever method you use, the combination of height and distance between LEDs should allow for a lot of overlap between adjacent LEDs.

I believe my colleague has a spacing equal to approximately the radius of the circle of illumination at the designed height from the board.

3. ### alper

9
0
Aug 5, 2016
Hi thanks for the reply. Do you know how can i calculate thoose distance for my project?

4. ### Bluejets

4,991
1,048
Oct 5, 2014
365nm LEDs will be the most expensive.

If you can get away with a broarder range of LED or ones up around 375-400 it will be a lot cheaper especially if the film on the board is made for the latter range.

For the focus, we made a unit here for curing a special type of epoxy in medical use and found there is a certain amount of visible light emitted. WE use that for focus and unit has been working now for over 10 years.

5. ### alper

9
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Aug 5, 2016
yes thats right its the most expensive actually but from where i live its cheaper than other lights. i can buy 10 led for a price of 1 fluorescent and plus more life span and less electric so i think its better option for my project

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Well, if they are indeed 120° LEDs, the spacing should be approximately equal to the height.

7. ### alper

9
0
Aug 5, 2016
yes they are 120 degree. so if the spacing between leds lets say
yes they are 120 degree. so if the spacing between leds lets say 5 cm then between leds and glass sold be 5cm too?

8. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
That would be a good place to start

9. ### alper

9
0
Aug 5, 2016
thanks i will start like this but how can i say if the leds are overlapping? or how can i prevent this?

10. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
You want the LEDs to overlap. This will have them overlapping significantly. Remember that the intensity falls off with angle. If they didn't overlap you'd have hot and cold spots all over the place.

11. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,497
2,839
Jan 21, 2010
You want the LEDs to overlap. This will have them overlapping significantly. Remember that the intensity falls off with angle. If they didn't overlap you'd have hot and cold spots all over the place.