My friend Jonathan said that he had a problem that was occurring very often after school and also on the weekends. His problem was that while he was playing League of Legends his mom walked in on him and then started to scream at him and confiscate his laptop meaning that nobody could play with him and he could not do his homework, for example technology submission. Therefore, I came up with the idea that he could become my client and I would therefore create an alarm sensor which would detect if somebody would be at his door.

(This cheap alarm sensor must not be used for this cause it can also be used for a different problem you are having.)

Step 1: Gathering All the Materials and Tools

The materials and tools you will need are a Materials/software needed for the Instructables: magnet, reed switch with alternating contact, nine volt battery with a battery clip, a switch, a screwdriver, a plastic box with four screws to close the box, a drilling machine, rubber connectors, tape, and a nine volt buzzer (the buzzer and battery clip already come with wires).

Step 2: Another Two Very Important Tools/materials

You will also need a soldering kit and some tin.

Step 3: Creating the Circuit #1

Now that you have all your materials set up take the reed switch and attach it to the nine volt battery and the nine volt buzzer. Please watch the video because it will show you how to attach the wires with tin and the soldering kit (can be found on the last page).

Step 4: Creating the Circuit #2

Now that the buzzer, the reed switch, and the battery are connected. You will only have to connect the on and off switch to the nine volt battery and to the nine volt buzzer. If you have forgotten what you did with tin in the last step, please watch the video because it will show you how to attach the wires with tin and the soldering kit (can be found on the last page). The circuit is now complete!

Step 5: Drilling a Hole Into Your Plastic Box

For this step you will have to drill a hole into your plastic box. It is important to drill the hole on a position that is easy reachable because the on and of button will go through this hole.

Step 6: Quick Check

For this step you should once more check if all of the wires are good in place and well attached! Then turn on the alarm, now you should hear a buzzer sound. If you do, put your magnet over the reed switch, the buzzer should now stop buzzing. However, if your alarm still doesn't work your battery might have no power or is broken (please check if your circuit is correctly done).

Step 7: Putting the Circuit Into the Box

For this step you will have to place the circuit into the box and tape it to the inside of the box so that the reed switch doesn't move. Lastly you will have to stick the on and of switch through your drilled hole.

Step 8: Screwing You Box Together

For this last step you will have to take four screws and then screw them tightly into the sides of the box so that the parts in the circuit will not fall out. Finally you should put your magnet over the reed switch, now your alarm will be ready to go!