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Picture of Homemade UV Exposure Box

This is an Instructable for a homemade UV exposure box that can be used for making PCBs.

Parts that you will need:

1x ATmega8 microcontroller

2x TIP31 NPN Power transistor

1x Voltage regulator 7805

1x voltage regulator 7812

1x 5v buzzer

2x 33uF capacitors

1x potentiometer

1x 32,756 kHz quartz crystal

1x 8x2 LCD

3x push buttons

1x power supply for laptops

1x power socket

a few cooling fans

UV leds from ebay

wood for the box

2x opaque white glass

2x normal clear glass

Step 1: UV LEDs

Picture of UV LEDs
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DSC08079.JPG

One can get a lot of UV LEDs from ebay: link

I realise that I probably did not need so many, but I used two boards, almost A4 in size with about 350 evenly spaced LEDs per board. One board will be used for the top exposure and the other for the bottom.

The most important thing to remember is that all these leds will require a bit of power. One can use the following calculator online to determine resistor values and led configuration: link

A UV led has a forward voltage drop of about 3.2V and should work at about 20mA

At the bottom of the page, after the calculation, the total current drawn from the supply is calculated. This is important because you now know the voltage output and max current output for the power supply. Also bear in mind that the TIP 31 transistor can handle a collector-emitter current of 1.5A, meaning that each board of leds cant go over that.

Also at such high currents, the transistors as well as the led boards get quite warm, so cooling fans are a good idea: link

Another point is that the leds focus on a spot, so you need to keep the leds quite far away from the exposing pcb (about 12cm). To make the distance smaller and to ensure a good, evenly diffused light, I used white frosted glass.

Another option is to use very high power UV leds, but I discovered these after I got my normal 5mm high-brights: link

hi, Great job but can you share the UV LED layout
thanks a lot for sharing your knowledge
MayP5 made it!2 years ago

Hi Chrismajda can you also include pcb display led i also want to make project in my school like you make thanks can you send it by my email

FNW39RII4PHJ71N.MEDIUM.jpg
barbara_xmn2 years ago

Hello, congratulations on the project !!! Would you like to make the led pcb file available? Also the cad file of the control? Thank you.

Amazing job!!!

Can you share a sketchup file of the box? I need to know the distance between both white frosted glass and the distance between one led and the other.

led.pngmedidas.png
chrismajda (author)  lucas.cuesta3 years ago
Good day, My apologies for the late reply. I opened up the Exposure Box and took the measurements for you:

- The 5mm diameter LEDs are placed 10mm apart from one another.
- The white frosted glass that I used is 160mm X 230mm X 4mm
- The distance from the led circuit board and the glass is 15mm.
- The distance from the glass to where the PCB to be exposed will be is 70mm.

So from your ?:
Shortest ? = 15mm
Middle ? = 74mm
Longest ? = 178mm

I have been experimenting a lot with UV exposure methods and can say that you don't have to worry too much about exact distances. The most important thing is to make a good quality mask and have a clean PCB when exposing. If there are any other questions, please feel free to ask. I promise to reply faster.

Kind Regards
Chris
DoctorWoo4 years ago

Love it! Do you happen to have a mock up of your PCB making process? I'd love to see that as well.

chrismajda (author)  DoctorWoo4 years ago
Thank you. I am glad you loke it. I plan to add a short video the next time I make a pcb. I can let you know when I have added it.
chrismajda (author)  chrismajda4 years ago

Hello there,

As promised, I have finally added a video of how the UV box is used to make PCBs.

Kind Regards

mat_fr4 years ago

Very cool and nicely done :)

I made one in an aluminum toolcase, adding a wooden structure to support the glasses. But I used a bunch of 1W UV LEDs (on a "star" base) and my choice of power supply was an ATX power supply with a relay "PCB" to turn it ON/OFF.

Too bad I didn't take pictures for an instructable as it was ongoing, now it's too late to show anything but the finished project :/

chrismajda (author)  mat_fr4 years ago
Thank you. I was regretting not using fewer, more powerful leds, but this works too... I also wanted to use an ATX but the laptop supply is smaller. Would love to see a pic of your finished project if you have one.

I'll try to make a small instructable with the few pictures I had taken at the time then :)

mat_fr mat_fr4 years ago

Ok, here is a quick and dirty instructable for a not so quick and very dirty UV Box ;)

https://www.instructables.com/id/Yet-Another-ugly-UV-exposure-Box/

Orngrimm4 years ago

Nice!

I bought my UV-leds back in the day from Aliexpress for a doller and a dime...

The good thing if you buy flat-dome-LEDs (7 us$-cents), is that they have a much broader angle of emission thus need less diffusion if at all. http://www.aliexpress.com/item/Wholesale-100pcs-lo...

If you want to go bazonkers, go get a 150W-UV-LED: http://www.aliexpress.com/item/150w-395nm-high-po... :)

I used a UV-cure-box for my 3d-Prints from my B9-Printer.

C-R-E-84 years ago
Cool idea ill just make one of the panels a door for bigger objects like a nitestick or so