Step 1: Materials and Tools
• Dry erase marker or something similar
• LED (Any color of your choosing)
• Thumb cells (3) and holder
• Tact switch
• Thin wire (Extremely important!)
• Soldering Iron and Solder
• Needle nose pliers
• Hot glue gun and glue
• Dremel with bits
Step 2: Gut the Marker
Step 3: Modify the End Cap
Warning! Now comes the difficult part!
Because the plastic material is thicker than the size of the button, you must cut a square into the plastic without going through the other side. The third picture matches what I am saying. You want to carve a square, slightly larger than the switch, so that when the switch is placed into the square the button protrudes on the other side. The tip of the button should be raised compared to the rest of the plastic. After you have successfully completed this step, set the cap and switch aside.
Step 4: Solder the Circuit
Time to warm up the soldering iron, because things are about to get hot! Okay, not entirely, but you get the point.
To start, if you haven't already, cut three pieces of wire all about the same size as the marker itself. For my circuit I chose to have two blacks and one red, just to help me know where the different leads of the LED are going. I started by soldering the positive wire (red) and negative wire (black) to the LED. Tip: For those who might have forgotten, the positive lead on the LED is longer, or if you have cut them, the negative lead next to the flat side. For this project I had made my own thumb cell holder (by request I could make an instructable on how to make one). Solder the positive wire from the LED to the positive terminal on the battery pack (or if you are skilled at soldering, right to the battery (dangerous though!)). Next, solder the negative wire from the LED to one lead on the switch, then solder another wire from the switch to the negative terminal on the battery pack.
And you are done with the soldering! Press the button and the LED should illuminate, if it doesn't check your wires and solder-jobs!
Step 5: Put It All Together
Still have the end cap set aside? Good, we will need it now. Place the button into the square you carved out (be sure the button protrudes on the other side!) and generously apply hot glue to hold it in place. Tip: Use a toothpick or tiny screwdriver to hold the button in place while the glue cools.
After the hot glue is cool, its time to put everything into the marker. Start by putting the LED into the back first; make sure to aim for the neck of the marker because thats where the LED needs to go! If you are struggling to get the LED into the neck, use a thin rod to push it into place. After the LED is in place, push in the batter pack positive terminal first, this is critical because then you only have one wire pressed against the batteries and marker! Next, insert the cap-switch combo into the end of the marker.
At this point the marker is complete, but in order for it to work perfectly we have to file down the bottom. This will allow for the cap to push the button firmly and ensure that the light stays on while in use.
Get a large file, wider than the markers base, and while holding the base flat against the file, file away small layers of the bottom. Check the depth using the cap, the perfect depth is one that allows the cap to press the button fully, but is stopped from going any farther by the end cap itself.
Bravo, you are done! Go out and illuminate all those dark areas, find those socks, or avoid falling down the stairs in dark hallway (or perhaps a cave?)!