Step 4: The LED array
When i first began the project, I figured a dozen or so high-intensity LEDs would be plenty. After all, perusing the LED lighting aisle at the local hardware store found several 4-LED lights that made everything very bright.
The difference appears to be that we're shining the light through water. Strangely enough, that takes a LOT more light than you would otherwise expect. I tried it initially with 8 LEDs, and the brightness was negligible. I then experimented with other numbers, and it quickly became apparent that I needed MANY more. How do you cheaply acquire lots of high-intensity LEDs?
I found a $10 LED spot light at a local store that did the trick. It had 60 of the little guys all installed in a series, so I only had to desolder them and they were mine!
Once I had all of the LEDs I needed, I began soldering them together. Since I knew I was going to power the whole thing with 12V, I knew I needed to install no less that 4 LEDs in series That will provide 3V each, which is under their 3.3V max. Yes, that means I'm not getting every single lumen of brightness, but it turned out to be just fine in the end, and I know I'm not overpowering the individual elements.
I took a piece of basswood and cut holes for a template to hold the LEDs. I then went through and soldered about 4" of light gauge copper wire across their leads. This proved to be the quicker way to do it, rather than soldering each individual wire on at a time. After soldering the wire across, I snipped out the 1/16" or so that was between the leads.
Afterward, install the LEDs between the power cables as you see fit. Again, this is very dependent on your particular application, but I provided a picture of how I did it below.