LED Flashlight With Secret Switch

With this project you are going to make a cheap DIY LED flashlight with no button on it. You will need a magnet to turn it on.

This project I did on a summer camp with a group of kids. (8 - 12 year olds) Everybody succeeded (some with some help from me) and we had loads of fun with it.

Parts:

• 1 PVC pipe (We use this in Europe to put electrical wiring in)
• 2 caps that are used for chair-legs and fit the PVC pipe
• 2 AA batteries
• some plastic
• foam-tape
• 1 LED
• 1 resistor
• 1 reed-switch
• 2 plan-board-magnets
• a piece of wire

Tools

• tape
• scissors
• pliers
• drill (size of your LED: 5mm?)
• needle
• sand-paper

Extra
For decorating you can use whatever you like:

• colored tape
• stickers
• markers

Prepare:
If you are going to do this with kids, you will need to do some preparations:

• Cut the PVC-pipe in the right length: just al little shorter than the two batteries and one of the magnets put end to end.
• Sand off the edges of the pipe, so the end caps will go on easier.
• Drill a (5mm?) hole in the middle of one of the end caps.
• Cut a piece of 10 cm wire.

You will need to do this once for every child that is going to make a flashlight.

Cutting het plastic sheet
The plastic will be a isolator between the anode of the LED and the battery. You can use any kind of plastic sheet you van find. I used a front-sheet that they use at Kinko's.

• You cut a square that is slidily smaller than the inside of the tube.
• Next you round it off so that it will fit inside the tube.
• To finish it, you will need to pinch a hole in the middle with the needle.

 

Adding the LED

• The anode (long leg) of the LED will be bent sideways.
• The cathode (short leg) has to go through the hole in the plastic "isolator" we just made.
• The anode will be bent 90° at the side of the "isolator" and folded back up. (see picture)
• The cathode is bent in a spiral that is flattened against the "isolator"

The reed-switch
A reed-switch is a switch that is activated by a magnet. They are cheep and small and everything with magnets is fun for kids!

• Fold both of the leads of the reed-switch in half to make a ring on each side.
• Hook the ring on one side of the reed-switch in the ring that you made on the anode of the LED.
• Tape the reed-switch on one of the batteries in a way the the reeds inside it are flat on the battery and the LED will touch the NEGATIVE side of the battery with its (spiral) cathode.

The resistor
Use a resistor that works for your LED with two 1,5 V (= 3 V) batteries. It will probably be a low value.

• Fold both leads the same way as you did on the reed-switch.
• Tape the two batteries together in a way that the negative site (-) of the second battery touches the positive (+) side of the first battery.
• Hook the resistor on the reed switch.
• Tape the resistor on the second battery.

The wire
The lead from the resistor is probably not long enough to reach the positive side (+) of the second battery. We will need to ad a piece of wire to reach it.

• Fold the end of the piece of wire.
• Hook the wire to the resistor.
• Tape the wire to the second battery.
• Fold the end of the wire around the end of the second battery so it can touch the positive pole (+) of the second battery.
• Cut of the access wire just past the positive pole (+) of the second battery.
• Stick the wire to the positive pole (+) of the second battery with a piece of foam-tape.

Does it work?
This is a nice moment to check if everything works. If you push the LED against the battery and you hold a magnet near the reed-swich, the LED should light.

NO

Mine didn't work. I used a broken LED, so I changed it for an other and tested it again.

YES!!!

Inserting

• Push the cap with the hole in it on one side of the PVC-tube.
• Insert the parts that are taped together in the PVC-tube, LED first.
• Wiggle it around until the LED pops out of the hole in the end cap. (some kids found this part hard to do)

The end cap

• Insert one magnet with the magnet pointing to the back of the flashlight in the tube. (Make sure the two magnets will attract each other. If they don't, you must pry one of the magnets loose and turn it around)
• Put on the end-cap and push it on really tight.

Finding the switch
The flashlight is finished now, but we will have to find the switch to turn it on.
To find it you go around the flashlight with the second magnet until the LED turns on. If you found it, it might be wise to mark the spot.

Decorating
To really finish it, this is the moment to decorate your flashlight. I gave my group several colors tape, stickers and markers and they made some nice designs. We had some glow in the dark stickers to mark the spot where the magnet had to touch the flashlight to turn it on.
Because there is also a magnet on the inside, you can "store" the magnet on the back of the flashlight.

We had loads of fun with it. I hope you do to!