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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

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

Step 2: Control Board

Attached are the files with the board design and the .hex file ready for flashing to the microcontroller.

The +16V socket is the input from the power supply whereas the +12V is an output for the cooling fans.

PIN C0 is reserved for future use.

Step 3: The Enclosure

The idea for this box is to place the pcb that is to be exposed with the transparent mask with the pattern between two glass sheets, like a sandwich, and to slide it into the box like an envelope.

I quite like this idea, because the box is then a sealed unit, and LEDs don't have the tendency to need replacing for quite a while anyway.

As always, planning is everything. Maybe draw the lines where the grooves will be and the holes before hand and see if everything fits before you start cutting. Take into account space needed for the power supply and the fans.

If you dont want cables getting caught on the glass as it is moving in, then you can hide connecting cables in a groove that will be covered by another piece of wood.

If the wood is too thick for the LCD of the push buttons, then mill out a depression with a router.

The microswitch is placed at the back where the glass with the pcb is inserted. This is to make sure that the pcb is fully inserted.

Dont forget side holes on the sides in the top and bottom compartments for the warm air to escape (if all fans are blowing inwards)

Step 4: Final Operation

For a normal photo resist, this box is able to expose the pcb in 45 seconds to 1 min:

I also use a solder mask layer (also from ebay) that needs 30 min of UV exposure for curing:

Solder mask link

A video of the UV box in action will be added at a later time when I make my next pcb.

I hope that this instructable was useful to you. This is my first instructable, so any feedback would be appreciated for future instructables.

Video of UV box in operation

<p>Hello, congratulations on the project !!! Would you like to make the led pcb file available? Also the cad file of the control? Thank you.</p>
<p>Amazing job!!!</p><p>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.</p>
Good day, My apologies for the late reply. I opened up the Exposure Box and took the measurements for you:<br> <br> - The 5mm diameter LEDs are placed 10mm apart from one another.<br> - The white frosted glass that I used is 160mm X 230mm X 4mm<br> - The distance from the led circuit board and the glass is 15mm.<br> - The distance from the glass to where the PCB to be exposed will be is 70mm.<br> <br> So from your ?:<br> Shortest ? = 15mm<br> Middle ? = 74mm<br> Longest ? = 178mm<br> <br> 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.<br> <br> Kind Regards<br> Chris
<p>Love it! Do you happen to have a mock up of your PCB making process? I'd love to see that as well.</p>
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.
<p>Hello there,</p><p>As promised, I have finally added a video of how the UV box is used to make PCBs.<br><br>Kind Regards</p>
<p>Very cool and nicely done :)</p><p>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 &quot;star&quot; base) and my choice of power supply was an ATX power supply with a relay &quot;PCB&quot; to turn it ON/OFF. </p><p>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 :/</p>
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.
<p>I'll try to make a small instructable with the few pictures I had taken at the time then :)</p>
<p>Ok, here is a quick and dirty instructable for a not so quick and very dirty UV Box ;) </p><p>https://www.instructables.com/id/Yet-Another-ugly-UV-exposure-Box/</p>
<p>Nice!</p><p>I bought my UV-leds back in the day from Aliexpress for a doller and a dime...</p><p>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. <a href="http://www.aliexpress.com/item/Wholesale-100pcs-lot-Brand-New-5mm-Infrared-Receiver-Diode-IR-LED-Free-shipping-10000358/836406032.html" rel="nofollow">http://www.aliexpress.com/item/Wholesale-100pcs-lo...</a></p><p>If you want to go bazonkers, go get a 150W-UV-LED: <a href="http://www.aliexpress.com/item/150w-395nm-high-power-uv-led-curing/2032062887.html" rel="nofollow"> http://www.aliexpress.com/item/150w-395nm-high-po...</a> :)</p><p>I used a UV-cure-box for my 3d-Prints from my B9-Printer.</p>
Cool idea ill just make one of the panels a door for bigger objects like a nitestick or so

About This Instructable

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Bio: My passion is to design PCBs and to program microcontrollers. I have a M.Sc. in Mechatronics Engineering and a B.Sc. in Mechanical Engineering.
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