| Room Alarm |
From "DIY Kids"
episode DIK-108 |
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You can make a alarm that buzzes when someone steps on the hidden foot switch. This simple electronics project is fun to make, especially if an adult works with you. Materials:
Construction paper or lightweight cardboard
Heavy-duty aluminum foil
Ruler
White glue
Tape measure
Wire strippers
Hook-up wire
Mini buzzer
Electrical tape
9-volt battery
Snap connector for the battery
Mounting tape (it's sticky on both sides)
Rug to hide the foot-operated switch
- The room alarm has four main parts: the foot-switch pad, the wire, the battery and the buzzer (figure A). As with any electrical project, you're making a circle of wire using metallic conductors. From one side of your foot-switch pad the wire goes to the battery. From the battery a wire goes to the buzzer, and the buzzer is wired to the other side of the switch. Until someone steps on the foot-switch pad, the electrical circuit is not a complete circle. Once the switch is depressed, electricity can flow through the circuit, and the buzzer will sound.
- Start by making a foot-switch pad. Fold a piece of construction paper in half so that the shortest sides meet. Press down on the fold well so you can see the crease when you unfold the paper.
- Cut two pieces of aluminum foil each about 7" by 5". Check to make sure they fit on each half of your piece of construction paper without touching at the folded edge. There should be about 1" of space between them in the middle (figure B). Set the paper aside.
- The foot-switch pad will be hidden under a rug, so you'll need to measure the distance between the rug and where you'll put your buzzer (figure C). Take this measurement and double it because the wire must go to the foot-switch pad and then back to the buzzer. Now add about 12" to the doubled measurement so you'll have enough wire to make all your connections.
- Cut hook-up wire to the measurement you determined in step 4. Fold the wire in half, and twist the wire together so it won't be messy (figure D). Begin twisting about 4" from the end of the loop, and leave a few inches untwisted at the end.
- Cut the loop of wire in the middle, and strip about 3" of the plastic coating from both cut ends of the loop, using wire strippers (figure E).
- Bend the two exposed wires on one end of your twisted wire into zigzags (figure F). This helps prevent the wire from pulling out easily.
- To finish making the foot-switch pad, apply a squiggle of white glue onto each piece of foil (figure G). Keep the glue away from the edges so that it won't squish out the sides when you press the foil onto the construction paper.
- Open the pad so it lies flat, and bend the two zigzags so they each rest on different sides of the crease. You want to make sure they do not touch. Turn one piece of foil, glue side down, onto your construction paper so that it covers the zigzag wire on that side, with almost an inch between the edge of the foil and the crease (figure H). Press down and smooth the foil from the middle to the edges so the glue covers the area well. Do the same thing on the other side of the foot-switch pad.
- When both sides are ready, with no glue oozing out, cover the foot-switch pad with something heavy, such as a big book, until the glue dries.
- To finish your room alarm, stick electrical tape around the outside edges of the aluminum foil and the construction paper (figure I).
- Cut three pieces of mounting tape long enough to reach from one edge of the pad to the other, parallel to the crease (figure J). Stick one piece next to the crease and a second next to the outside edge. The third piece goes in the middle.
- Peel off the paper covering the top side of the tape, and fold over the other side of the switch so it sticks to the tape (figure K). The tape is thick enough to hold the two pieces of aluminum foil apart (figure L) until someone steps on the foot-switch pad.
- Strip about 1" of the plastic covering from the ends of the long twisted wire. Do the same to the buzzer wire and the battery connector wire. Twist one of the ends of the long wire onto the buzzer's black wire. Cover the connection with electrical tape so the wires don't show. Do the same for all connections. Twist the buzzer's red wire to the connector's red wire (figure M).
- The black wire from the connector and the other end of the twisted wire are the only two left, so it's easy to figure out the last connection. The final step is to add a battery to the snap connector (figure N).
- Put the foot switch under a rug, and hide the buzzer. The next time someone steps into your room, the buzzer will sound the alarm.
RESOURCES :
Science Crafts for Kids: 50 Fantastic Things to Invent and Create
Model: 0806902841
Author: Gwen Diehn & Terry Krautwurst (Contributor)
(1997)
To order this title from Amazon.com, click here.
Sterling Publishing Co. Inc.
Website: www.sterlingpub.com
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