Step 4: Installing the switch
Now the switch. One the switch are three connectors; load, power, GND. GND seems obvious. Load is the power to the light which is the -12V (blue) wire for us. Power will be the green wire. The green wire doesn't really have more than a miniscule amount of power on it, but this gets us connected to the GND.
The types of switches available is huge. I bought mine at the auto store which sometime means they've got a fuse. Good thing? Depends on the size. This amp can pull 16.67 Amps at peak when at 12 V. You can find this info in your manual by finding the peak wattage then dividing by 12 (the voltage you will be running at assuming your PSU is running at optimal voltages). My 200 Watt (2 x 100) AMP can therefore pull (200/12=16.666666....) just under 17 Amps. Some of these switches end to have very small fuses of 10 or 15. Be aware of this at purchase.
Be sure to find one that COMES WITH a mounting connection of some type. Mine is a small screw-type connector, it leaves an awful lot of switch up front but I was determined not to buy anything for this project when I had so much lying around.
The hardest thing here was not deciding where to put my switch, it was cutting a round whole in cardboard. I got my best knife and just worked a small square then rounded it out until I reached the size I needed. I also surrounded the whole with tape and even put a little through that is under the switch where it can't be seen.
TEST YOUR CONNECTIONS!! If everything works you can close her up.