Making The Exposure Unit.

There is one major thing I got very wrong in making this exposure unit. I ordered inadvertantly waterproof IP67 SMD5050 LED strip lights. So before I could even begin putting it together I had to remove 10 meters of silcone shielding off the cables, which was extremely tedious. Once that was completed, I was ready to start making the exposure unit.

The first step was to cut out a bit of hardboard (thin plywood would work equally well) to fit the exact dimensions of the interior of the Eurobox (see previous blog post) of 55cm by 35cm. Then I covered the smooth side of the hardboard in aluminium tape. This helps to reflect light and hence reduce exposure times aswell as helping the strip lights adhere to the surface.

From here on in it gets a lot more laborious. 

1: Cut the strip lights into 50cm sections. After every 50cm the strip lights have a soldered join. Carefully cut through with very sharp scissiors right through the middle of each soldered joint making 50cm sections of strip light. You will end up with twenty, 50cm lengths of LED strip light. 

2: It's time to start marking out on the aluminium taped box where the strips will be placed. Using a Sharpie or similar mark out 2.5cm from each side of the aluminium tape covered top panel. This will leave an area for your strip lights to go that is excactly 30cm x 50cm (big enough for an A3 sized exposure). Once you have done this along the length, axis mark 1.5cm increments along the two short sides and mark a line between each end with your Sharpie. This will give you 20 'gaps' for where to place your 20 lengths of 50cm strip lights. 

3: Now it's time to put the strip lights in. If like me you stupidly purchased the waterproof LED's, at this point you'll need to cut 20, 50cm lengths of double sided tape. Assuming you purchased the non waterproof lights which are self adhesive peel off the backing paper and place each 50cm strip between each of the lines, making sure that each strip is going in the same direction of current (ie: +/- to +/-) along the whole width of the panel. On the strip lights you'll notice a +/- is printed at the soldered joints. 

4: The strip lights aren't designed to work in more than 5 meter lengths. If they are wired in series for a whole 10 meter length you'll get voltage drop out. Basically the end of the strips furthest away from the power supply will be dimmer than the ones closest to the power supply, meaning each 5 meters of strip light will need to be wired seperately into the power supply. I only discovered this once I had made it, however a little bit of resoldering rectified the issue quickly. 

5: Once you have placed all the strips in series it's time to solder all the strips together. This is where I discovered that I hate soldering. If you haven't soldered before give yourself a crash course by watching a YouTube video or something.

The first 10 lengths need to be soldered together, always making sure you go from positive on one length to positive on the next and the same with the negative terminals, on both ends of the 50cm strips.

6: First prepare 20x black wires of about 4cm and the same with red wires. It's handy to use different coloured wires to help ensure you don't mix up polarities. Once you have you 40 lengths of insulated wire you'll need to strip about 5mm of each end to expose the wire. 

7: Now solder the first 10 strips together at both ends, as stated before going from + to + and - to - at each end until you have done 10 strips. Between the 10th and 11th strip make sure they are not connected to each other. Then repeat the process for the 11th to 20th strip. See images below.

NB* the two middle strips are not soldered as both 5 meter strips will be directly attached to the power supply. 

8: If you have got this far, most of the hard work is over. On the end of each 5 meter strip solder wires long enough to go into the DC supply. 

You'll need a 12V / 10A supply as SMD5050 LED strips require circa 1 amp per meter. 

9: Glue or use sticky pads to attach the LED panel to the bottom of the Box. 

10: Drill a hole just big enough to form a tight fit for the DC cable for fit snuggly. 

11: Wire the two positive cables of each 5m strip to the positive connection on the DC supply and do the same with the negative. 

See image below.

Now it's time to plug it in and make some prints.

At a later stage I will attach an on/off switch and a timer would obviously be incredibly useful.

Happy printing..