Burglar Alarm
How can we use basic knowledge of how circuits work to construct a simple appliance? This burglar alarm is easy to understand based on knowledge of circuits and switches.
What You Need
These are the materials required to make one burglar alarm. You will need to modify depending on how many alarms you wish to make.
- 4"x4" cardboard
- Piece of thin cardboard
- Aluminum pie plate
- String
- Boot-shape template (see guide)
- Clothing pin
- 3 elastic bands (white, red, brown)
- 3 paper clips
- Thumb tack
- 2 wires
- AA battery and holder
- Buzzer
Guide:
What To Do
- Place the battery holder on the cardboard base in the upper right corner - see Figure 2 on page 9 of the attachment.
- Poke two holes, one on either side of the battery pack - see Figure 3 on page 9 of the attachment.
- Loop the elastic band through the two holes and secure them on the back with the paper clip - see Figure 4 and 5 on page 10 of the attachment. Slot the battery back through - see Figure 6 on page 10 of the attachment. It should be securely fastened to the cardboard.
- Place the clothing pin on the cardboard and poke two holes on either side like before. Loop the white elastic band through and secure on the back with the paper clip - see Figure 7 on page 10 of the attachment.
- Place the buzzer on the cardboard and poke two holes as shown in - Figure 8 on page 11 of the attachment. Loop the brown elastic band through and secure on the back with the paper clip.
- Place the boot-shape template on the pie plate and cut out two pieces. Poke a hole in each tip as on the picture see - Figures 9 and 10 on page 11 of the attachment
- Tape the aluminum cut-outs to the clothing pin as shown in Figure 11 on page 11 of the attachment. One cut-out goes on the top, and the other on the bottom. The tips should face opposite sides - see Figure 12 on page 11 of the attachment
- Figure 13 on page 12 of the attachment shows what you should have set-up so far.
- Cut a small square/rectangle from the thin cardboard and poke a hole near the edge. Tie the string around the hole. Tie the other end of the string to the thumb tack -see Figure 14 on page 12 of the attachment.
- Take one wire and attach to the negative end of the battery pack. The other end of the wire attach to one of the boots on the clothing pin - see Figure 15 on page 12 of the attachment.
- Next, attach the black wire from the buzzer to the other boot on the clothing pin - see Figure 16 on page 13 of the attachment.
- Take the other wire and attach it to the positive end of the battery pack see - Figure 17 on page 13 of the attachment.
- Before connecting the last wires, insert the cardboard cut-out in between the two aluminum boots on the clothing pin - see Figure 18 on page 13 of the attachment.
- Lastly, attach the positive wire from the battery pack to the red wire of the buzzer see - Figure 19 on page 14 of the attachment.
TEST IT OUT!
Discovery
The wire from the negative side of the battery travels to the aluminum boot of the clothing pin. Then from the other clothing pin the electrons travel to the buzzer. Then from the buzzer the electrons travel to the positive side of the battery. Since we disrupt the electron flow with the cardboard between the two boots of the clothing pin they can not travel to complete the circuit and sound the buzzer. When somebody opens the door - pulling the string attached to the cardboard disrupting the circuit - the circuit becomes closed allowing for electrons to flow through which sounds the buzzer on our alarm!
What's Happening?
The wire from the negative side of the battery travels to the aluminum boot of the clothing pin. Then from the other clothing pin the electrons travel to the buzzer. Then from the buzzer the electrons travel to the positive side of the battery. Since we disrupt the electron flow with the cardboard between the two boots of the clothing pin they can not travel to complete the circuit and sound the buzzer. When somebody opens the door - pulling the string attached to the cardboard disrupting the circuit - the circuit becomes closed allowing for electrons to flow through which sounds the buzzer on our alarm!