UV LED Exposure Box

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by djhamer
 

introUV LED Exposure Box

How to build an Ultra Violet Exposure box using LED's.

Your last Veroboard project!

A UV exposure box is an extremely useful piece of kit. It can be used to make proper PCB's. It can also be used to make other things such as intricate photo etched parts (a subject for another instructable). The trouble is they can be a little pricey for the hobby enthusiast especially if you want the double side type.
This instructable outlines the construction of a double sided UV exposure box using the recent generation of high brightness UV LEDs.

Why use LEDs?
LEDs are far more energy efficient than either incandescent or fluorescent lamps offering between 5-10 times more efficiency making them cheaper to run and kinder to the environment. They also (unlike fluorescent tubes) do not contain mercury. LEDs have a far greater life span than the other types of lamp measured in decades rather than months. The frequencies being emitted are also in a tighter band making UV LEDs safer than the traditional UV tubes. There's also just something cool about LEDs, I can't put my finger on it, but ever since I was a kid I've found them to be one of the more fascinating electronic components.

Is there a disadvantage to using LEDs?
Not really, however the UV exposure box I have detailed here is a little less powerful than the commercially available ones. This means that your exposure times will be around 2 ~ 3 minutes as opposed to 30 ~ 40 seconds, but come on, do you really need your PCB's to be produced that quickly? Anyway sometimes having a slightly slower exposure time can be an advantage allowing you a little more control.

This UV Exposure box will consist of 2 UV panels; each having 84 LEDs a total of 168 LEDs. Each panel will draw about 700mA at 12v. This makes each panel 8.4watts a total of 16.8 watts for the whole thing.
UV LED Exposure Box
UVLEDExposureBox.jpgUVboxLit.jpgUVboxOff.jpgFluorescein.jpg
 
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step 1Materials

The most critical parts of this project are the UV LEDs, you are looking for 5mm Ultra Violet LED 2000mcd 395nm, 3.4V 20~25mA.
I bought two 100psc packs from eBay.
If you find something better then ensure that they are;
- At least 2000mcd in brightness
- Have a peak wavelength of less than 400nm.
- A viewing angle of at least 20 degrees.

You will also need 2x 160mm x 100mm pieces of Veroboard and 56x 75R resistors.
Another important choice is the PSU. I used a plug in, 12 volt 24 watt switch mode power supply. Switch mode power supply's are far more energy efficient than most other types and are also very stable.

All the other parts and materials are easy to find. Some I bought, some I salvaged. This is where you own judgement and taste comes in. In the end it's up to you how closely you follow my design. I've included all the CAD drawings and schematics as metafiles so they're easier to read when you print them out.
Materials
UV-LEDs.jpgPSU.jpg
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74 comments
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Aug 12, 2010. 9:49 AMf2a says:
Nice design, however it wasn't big enough for me. Also I didn't need to do double sided boards. I made a uv light box out of a cigar box that turned out great. Here are some pictures if interested:
052.JPG045.JPG044.JPG006.JPG
Aug 15, 2010. 1:22 PMf2a says:
No I haven't made any pcbs yet, but I'll post some pictures when I do! I should add, if you are going to make one out of a cigar box you have to use flat top leds. Otherwise the light won't be even. With flat top leds you can get even light from much closer which should also allow for quick exposure times due to higher power. I also cut a piece of acrylic to fit inside the box to flatten the transparency onto the pcb. Does anyone have any good eagle test patterns? I need to make one so I can do some tests.
Jul 7, 2010. 7:52 PMVogavt says:
I built the box, but I seem to keep blowing LED's. I'm using the supplier that you recommeded and everything appears to be okay. However, I noticed that when I turn off the wall-wart type 12v power supply, I have some latent voltage residing on the board. I can see some residual glowing of some of the LED's immediately after turning the unit off. It does eventually fade out, but if I turn the unit back on too quickly, I have a bright flash of the LED's. It's as if there is a capacitor somewhere that's holding current in the 12v transformer. Any ideas or suggestions to bleed off the current? I'm a newbie at these sort of things.
Jul 11, 2010. 5:33 AMVogavt says:
Okay. After surfing around the web I've found out what a "Bleed Resistor" is, but I haven't been able to find out definitively how to calculate the amount of resistance needed or exactly where to put it in the circuitry. Any suggestions would be welcomed.
Jul 7, 2010. 2:24 AMhamstanz says:
Do you not mean 200 mcd brightness ?
Aug 13, 2010. 2:35 AMcasper_2010 says:
hi there, i was wondering how big your veroboards are? seems like a great instructable, just ordered myself some uv leds to make one cheers
Jun 24, 2010. 12:34 PMbogdanfirst says:
I have made a similar UV box, with some improvement, too! Thanks for the idea! Check it out: http://www.electrobob.com/uv-exposure-box-part-1-the-box/
Jun 25, 2010. 3:44 PMbogdanfirst says:
That switch provides a simple and effective way to make it safe, as long as nobody tampers with it, goggles are harder to obtain and cost more. These safety measures should come as a second protection, first line is actually us, not opening the box and staring at uv lights turned on.
Jun 17, 2010. 7:35 PMMunchys says:
Could i tan my finger in this?
May 10, 2010. 12:15 PMphoenix62_80 says:
Great work, thanks for the instructable. I'm in the process of getting all the kit together to build one.  As a point though the photograph of the resistor is of a 65 ohm resistor and not 75 ohm as mentioned in the text.  65 ohm resistors are quite hard to get hold of!
Jun 3, 2010. 3:37 PMphoenix62_80 says:
I agree with what you have typed, the colours you mention definitely are the code for a 75 ohm resistor, however the picture you have submitted in the instructable to my eyes clearly shows a 65 ohm resistor - blue(6), green(5), black(*1) and thats what I was trying to point out. 
May 23, 2010. 7:59 PMyazid says:
great instructable. thanks, i love it. but i have a question, can i use this to expose photo emulsion silkscreen, because i see some of them using black light tubes. will LEDs work? thanks in advance.
May 13, 2010. 3:48 PMconoral11 says:
I found it difficult making these dog legged bends. I simply placed the resistor through the holes as usual, Soldered them in then bent the reamaining leg back and forth.

As the metal tired out it snapped flush with the top side of the veroboard. Hope that helps anyone.
Jan 21, 2010. 5:31 AMHeartman says:
Hi,

I made one simple face in 2007,
Link (French Forum) : http://soj.mesdiscussions.net/soj/Electronique/Montage/projet-insoleuse-digital-sujet_5067_1.htm



With schema and explanations, with a Pic Timer (2 versions are presented).

I'm working one another version double face,
with 28 000mcd UV LED 8mm 140° angle.
I guess 10 LEDs per face will be right.

My best regards,
imgp1237jy7.th.jpg
May 9, 2010. 12:00 AMBilldo22 says:
if you connected it in a certain way couldnt you power it with AC?
Dec 29, 2009. 4:52 PMjtrowbridge says:
How did you find the optimal distance for exposure between the PCB being exposed and the LED boards?
Dec 18, 2009. 8:24 AMfarrelan says:
Very hard to read your measurements. You have a better pic that you can send me??
Dec 21, 2009. 7:47 AMfarrelan says:
Thanks alot. Learn something everyday
Dec 7, 2009. 1:02 AMkal00 says:
Stupid question: How do you make pcb's out of uv light? Do you need a special copper clad that has a photoresist material? 
Dec 13, 2009. 1:58 PMkal00 says:
Thanks for the reply, looking forward to the timer! Keep up the great work. 
Dec 9, 2009. 5:16 PMelinventor21 says:
hello guys there seems to be a problem but i cant seem to download the pdf for ofline viewing it says that its corrupt or something any tips?
Sep 17, 2009. 9:55 AMstevecooley says:
Aug 28, 2009. 11:41 AMGM2009 says:
-Disadvantage of this design compared to clasic UV tube is size of the board. But if you are not making any larger boards, this is good. And size can be increased, but cost to. -I am not sure but glass from old scanner or copy machine should not be blocking UV light? There is on instructable with an old scanner and UV bulbs. Only thing with a scanner is that there is probably not enough distance between glas and top of bulbs.
Jul 12, 2009. 9:43 AMJoachim Bates says:
I am still a beginner but I have done some research on PCB's. I really like this Instructable and I think I am going to use it Joachim
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