Chocolate Egg Protector

Build an alarm to prevent your treats or chocolate from mysteriously going missing.

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things you will need

 
The following items from the Discover Circuits kit:
  • 1 x 4AA battery pack (and batteries)
  • Buzzer
  • 2 x black croc leads
  • 1 x red croc lead
  • Switch
  • Sticky tape (double-sided if you have it)
  • A jar with a lid
…and some of your favourite treats to protect. Yummy!
1

Connect to power

Connect one red croc clip to the red wire of the battery pack and one black croc clip to the black wire of the battery pack.

2

Add the switch

  • Connect the black croc clip attached to the battery pack to the pin on the switch labelled COM (this stands for Common).
  • Take another black croc clip lead and connect it to the pin on the switch labelled NC (this stands for Normally Closed).

Things to know

Wiring to NC (Normally Closed) will make the buzzer sound until the switch is pressed.

Wiring to NO (Normally Open) would make the buzzer sound only when the switch was pressed.

3

Add the buzzer

  • Connect the red croc clip attached to the battery pack to the red wire of the buzzer.
  • Connect the black croc clip attached to the switch to the black wire of the buzzer.
4

Test it out

  • Turn the battery pack ON.
  • You should hear the buzzer loud and clear.
  • To stop the buzzer press down on the lever of the switch.
!

Top tip

If the buzzer fails to sound, check that all the wires are connected correctly - red to red, black to black.

5

Set-up the alarm

  • Take the lid off the jar.
  • Attach sticky tape to the switch.
  • Secure the switch (with the lever facing upwards) to the inside of the jar, just below where the lid reaches when placed on top of the jar.
  • Turn the battery pack ON.
  • Place the lid on top of the jar.
  • The alarm should turn OFF when the lid is placed on the jar and turn ON when the lid is lifted off the jar.
!

Top tip

It will take a few goes to get the switch in just the right location for the lid to close the switch. When it's working, secure firmly in place with some extra sticky tape.

6

Add the treats and WAIT!

  • Take the lid off the jar.
  • Add the treats that you would like to protect.
  • Place the lid on top of the jar.
  • You will now be alerted by the buzzer if anyone tries to help themselves.

How it works

Switches control the flow of electricity by opening and closing circuits to make or break a loop.

When a switch is closed (ON), the loop is complete and electrons can travel around the circuit.

When a switch is open (OFF), there is a gap in the loop and electrons cannot travel around the circuit.

In this circuit, the switch has been wired to NC (Normally Closed), which means that the loop is complete and the buzzer will sound until the switch is pressed and a gap in the circuit is created.

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