UV exposure Box

ello, this project goes through the construction of a simple stand alone Ultra-Violet exposure box.

Ever come across large and complex schematics or wanted to take advantage of ready PCB layouts included in tutorials and projects? Well if yes, then this UV Box may help you solve that problem. I 've always liked developing my own circuits for any project, but as you take more advanced projects, more complicated circuitry with lots of more connections may be required. It may take effort and time to draw and etch a PCB, however the outcome is much more satisfactory!

A UV box is used to expose photo-resist boards in order to etch a printed circuit board for hobby electronics.

Please take note since it is not advised to expose or etch very detailed PCB's for it may fail to expose tiny gaps. This guide explains every part of the UV Box, it includes schematics, code and used parts.

Step 1: Find a Box

The first thing that must be done is to acquire a box. Dimensions are chosen by user, think of how big PCBs you want to etch and find/make a box depending on your needs.

• It is advised to get a simple shaped box (unlike the one used here), this will help with the positioning and modding of the box.
• The inner space is divided into two parts. electronics and expose area. Since the design is on your hands you could place all electronics below the LED panel to get the most out of your space.
• Think of where the glass will go and don't place it to close to the panel due to the led light angle (which is usually about 30 degrees).
• In this box the approximate dimensions for the led part is about: 17cm x 14cm x 12cm(height) pay attention on height for you need to be sure the board will be evenly exposed from the panel.

Step 2: LED Panel

Lets start from the easy parts. Find lots of Ultraviolet leds (here used 80). Solder them in parallel and then add a resistor in series (anode or cathode doesn't matter).

Calculating resistor: Determine the voltage of the supply (Here 5 volts) and use Ohms law or online calculators. Or you could do it the old fashioned way.

R= (SupplyVolt. - LEDvolt) / (LEDcurrent * num of leds)

*The number of the leds you will use will mostly determine the ratings of your power supply for your project. In this project, power needs is about 3 Amps for everything. Warning: placed resistor must be capable of driving as much current as the led panel needs (in my case is 5 Watts).

Step 3: Power Supply

The most crucial part of the supply is the transformer, it must be able to provide lots of current.

Parts list:

• Transformer: mains power to 12V 3Amps
• LT1083CP linear regulator
• Diode bridge rectifier (Capable of 3Amps)
• 280 ohm Resistor 1%
• 100 ohm Resistor 1%
• 10uF electrolytic Capacitor (2 pieces)
• Double Slots Terminal Blocks (2 pieces)

The LT1083 is an adjustable linear regulator and uses 2 resistors (Voltage divider circuit) to determine the output voltage. They are about 3/1 to get an approximate of 5 volts output.

Schematic included in photos.

Step 4: Microcontroller

n order to make this project more automatic, a microcontroller board has been added. You could use an arduino instead.

Parts List:

• Microcontroller Pic-16f876a
• Buzzer
• Text-LCD-monitor 2x16
• 10 Kohm Resistor (4 pieces)
• TIP142 Transistor
• 4 kHz Crystal or Resonator
• 28 pin IC socket
• Headers (Male/Female) (Lots)
• Rotor encoder (Aski rotor encoder)
• Knob
• *For common crystal clock sources, 22pF Capacitors (2 pieces) are also needed.

Link for code: https://github.com/ChrisMeletis/pic-uv-exposure-box

Code and Schematic included (compiled in MikroC and may not be compatible with arduino)

Step 5: Cut Drill Assemble

Since I forgot to take pictures during the box modding, I haven't included a step-by-step assembly. But there is no need since you plan and decide what goes where.

Use lots of cables for the connections between the boards screws and spacers to hold each board in place where you need them.

Step 6: Expose!

ter you finished building the UV Box you can try expose and etch your first board. For testing purposes I've included a board schematic. I've also uploaded an image tip for board placing.

For etching you need to:

-Print your board onto a transparent sheet. (like printing on paper)

-Place your schematic over and between glass and board. Caution on which side you'll place the board schematic. If you miss-side your schematic you will end up with an opposite board.

-Peel off the protective cover in a low light environment in order to avoid spoiling your board.

-Place the naked board over glass and copper side towards the led panel.

-Finally just expose for 10 to 15 minutes. (12mins Works for me).

Watch out luminescence capabilities of your IR led panel or IR lamp since it plays a master role for the exposure time. Brighter light means less exposure time.

I will not go through the explaining of the etching method or the PCB design since there are many great inscrutables that could help you.