Make a Homemade Flashlight!


One of the more memorable school projects I encountered during my youth was the building of a flashlight from scratch. It taught me a lot about electricity and showed that what might seem like a mysterious, unfathomable device was often more simple that it appeared. That led to the understanding that even complex equipment could be comprehended if you studied hard enough.

You can acquire the same understanding by making your own flashlight, with the bonus of having the flashlight to use when you're done. It's not difficult, and it's not very expensive, either.


You might need to make a trip to Radio Shack for this project.
Figure 1. The supplies you'll need.
The materials are simple and readily available:

That's all you need. The flashlight bulb can be obtained almost anywhere; Radio Shack or an Auto Parts store are sure bets.


Fold the aluminum foil and cut two cardboard circles.
Figure 2. Prepare the materials
  1. Cut two circles from the flat piece of cardboard. These will be used as the ends of the flashlight. Cut a 1/2 slit in the center of one and carefully poke a hole in the center of the other. Take two pieces of aluminim foil and fold them 4 or 5 times until you have two long strips about 12 inches by 1/2 inch each. Cut the cardboard tube to just slightly longer than the length of the two batteries together. See figure 2.

    Putting the pieces together.
    Figure 3. Putting it all together.

  2. Slip one of the aluminum strips about 3 inches into the cardboard circle with the slit in it. Fold the short end of the aluminum so that it makes a small square bump. Insert the light bulb into the hole in the other cardboard circle. Carefully wrap one end of the other aluminum strip around the metal side of the bulb's base. Be sure that the aluminum does not touch the metal tip on the bottom of the bulb. Insert the two batteries into the cardboard tube. (Make sure the batteries both point the same way.) Figure 3 shows these parts.

    The two cardboard circles fit on either end of the tube, while the aluminum strips go along the side of the tube.
    Figure 4. Assembling the flashlight.

  3. Fit the two cardboard circles on the end of the tube to hold the batteries in place. Make sure that the bottom tip of the bulb and the aluminum square touch the ends of the batteries. Tape the circles in place with the masking tape. Tape the aluminum strips along the side of the tube so that they meet and over lap about an inch or two. Leave the end of one strip free so that it can be bent back to avoid touching the other strip. See figure 4.

    Each cup (except the end cups) is filled with 3 markers.
    Figure 5. Ready to use!

  4. Turn the flashlight on by pressing the the two aluminum strips together. If it doesn't light up, make sure that: To turn it off, simply fold back one of the aluminum strips so that they no longer touch.

  5. Turn out the lights and have fun!

How it works

Electricity flows through metals or other conductive materials. When you connect the two ends of a battery with a conductive material, current flows through the circuit. If there is nothing in the circuit besides the battery and the conductor, the current flows very freely, resulting in a drained battery, a very hot conductor, and possibly a fire. This is often called a short circuit.

To prevent this, a cuircuit should include some sort of load or resistance to slow the current down. This is usually accomplished by making the current do some sort of work -- in the case of a flashlight, that work is lighting the bulb.

In this flashlight, we are using two batteries in series for a little more oomph. Just as two train locomotives together can pull a longer train, two batteries can do more work.

To turn the flashlight on and off, we open the circuit by separating the two strips of aluminum. If there is not a complete path from one end of the battery to the other, no current will flow.

Updated: Sept 9, 1999 Roger Louis Sinasohn and Associates Uncle Roger