Introduction: LED Night Pen

In this Instructable I will show you how to make a pen that lights up when you press a button on it. I am a lazy person who doesn’t like to turn on the lights when I’m using the computer, and so I thought it might also be handy to be able to write in the dark. The picture in the last step shows the pen at work (Don’t worry; it’s not actually as bright as it looks in the photo!). Warning: Glue guns and soldering irons get hot; I can’t be responsible if you burn yourself.

Step 1: Gathering Supplies

For this Instructable you will need:
• one ordinary stick pen with a plastic case (not metal)
• one switch (the kind you find inside a computer mouse; look at the first few pictures)
• one USB cord long enough for easy use on table or desk while in reach of the USB port
• one LED
• wire (for leads on the LED)
• newspaper to protect the floor

• a dremel tool or a drill with which you can cut the plastic pen casing
• a soldering iron, unless you’ve already removed the switch from the mouse
• a hot glue gun with glue sticks
• scissors or wire strippers
• an electrical tester

Step 2: Preparing the Pen 1

Pry off the end of the pen with scissors as in the picture.

Step 3: Preparing the Pen 2

Drill holes in the pen in the shapes and places shown in the picture. Be careful not to drill clear through both sides of the pen, but only on the side nearest you.

Step 4: The USB Cord

Take the USB cord and strip off 1½ “– 2” (4 – 5 cm) of the outside insulation. Take the red and black wires and strip off ½ “(1 cm) of the insulation on their ends. Take the other two wires and cut them off short as in the picture. (They are information wires and we won’t be using them for this project.)

Step 5: Removing the Switch

If your switch has already been removed from the mouse / whatever, you can skip this step. Heat up the soldering iron and hold it against the soldered points and, when the solder has melted, pull the switch off the circuit board with pliers or your fingers. (It might be a bit hot, so be careful.)

Step 6: Putting Back the Workings

Re-place the ink cartridge in the pen in its original place, and re-cap the “rear” end of the pen.

Step 7: The Switch

Push the end of the USB cord through the hole at the rear end of the pen, and down the case until you can grab it through your square hole half-way down (one which you drilled earlier). Take your electrical tester and set it to resistance test and find out which two of the three wires coming out of your switch you want to use. (You want to use the wires which conduct electricity when you press the button on the switch.) Take one of the two USB wires at the end and glue the very tip of the wire onto the switch beside one of the two terminals. Wrap the uninsulated part tightly around the terminal and then, when you get to the insulated part, glue it to the switch beside the tip. (See photo.)
Go back to this step when you’re done the next step, and fasten the LED wire onto the switch in the same way.

Step 8: The LED

This step should be fairly easy. If you know how to solder, you can solder two wires onto the wires of the LED or, if you don’t, you can simply wrap the wires around each other and secure them with glue-gun glue.
This is a very important bit: plug the USB into your computer and fasten the LED wires to the wires coming from the USB. You might have to switch them around, since LED’s only light up if they are hooked up in the right direction. REMEMBER WHICH WIRE SHOULD GO ON THE SWITCH SIDE OF THE CIRCUIT!
Returning to the previous step for guidance, put the wires through the hole near the tip of the pen, run them up to the little square hole, pull them out, and fasten the appropriate LED wire onto the switch wire.

Step 9: Gluing Things in 1

Twist the other LED wire and the USB wire together and cover the connection with glue. (Don’t use much, or it won’t fit into the case!) Tuck all of the wires into the pen case and glue the switch in place in the square hole, seating it as far in as it will go before it hits the cartridge or wires.

Step 10: Gluing Things in 2

If the LED wires are sticking out of the LED hole at the tip of the pen, tuck them into the case and then glue the LED so that it sticks out perpendicularly to the pen. (See photo.)

Step 11: Finish

If you did it all right, your pen should look like the pen in the photo.

Step 12: Enjoy!

Do exactly as the title says! Now you won’t have to turn on the lights when you need to jot a note near the computer.    :-)

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