Morse Code Buzzer

I visited Bletchley Park near Milton Keynes recently to deliver some practical workshops involving Morse Code messages. The idea behind the activity was to receive and decode a Morse message then use the information to find the position of an enemy U-Boat ‘wolfpack’ in the Atlantic Ocean.

Many thanks to all of the family groups who joined in the fun and a special thanks to the couple who helped us try out the idea before the family groups arrived. We had a great day!

Here is the buzzer circuit we made....

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note: The buzzer was held in place by another elastic band doubled around it and the foam block instead of using two paper fasteners as shown in this picture!

The single paper fastener can be used as a switch to make the buzzer ‘bleep’ by touching it across the heads of the two fasteners in the end of the foam block.

Here is the sequence of steps in making the buzzer circuit...

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Note: Above are the parts used. The 4 brown tubes are called sleeves and they are used to join the bare wires to the paper fasteners. Two elastic bands are used!

Make sure you read all of the instructions and study all of the pictures before trying the first step!

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The single black wire and the two wires from the buzzer are ‘stranded’ and the first job is to pull off the plastic insulation from the ends and twist the thin wire strands together to strengthen them. The picture on the right shows the black wire with the bare ends already twisted and ready to join to a paper fastener - one fastener fits on each end. After the buzzer wires have been twisted to strengthen them they are also joined to fasteners using the sleeves to hold them together.

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Look closely at the point where the head of the paper fastener touches the brown sleeve and you see that the end of the bare wire is just visible and it has been ‘hooked’ over to prevent it sliding back out of the sleeve - make sure you hook all of the wires like this.

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Place the battery in the hole in the foam block and double one of the elastics around it. Make sure you recognize the + (positive) and - (negative) of the battery. The + of the battery has the bump or cap on the end and the - is flat.
use a pencil to ‘drill’ two holes in the end of the foam block as shown. The holes need only be as deep as the brown sleeves.

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Place the block such that the negative end(flat) of the battery is visible as in this picture. The single black wire is going to be connected to it. Double back the black wire where it enters the sleeve then push the wire and sleeve into the hole nearest the negative end of the battery until only the head of the fastener is visible above the foam. Lift the elastic band and trap the sleeve and fastener on the other end of the wire such that the head of the fastener touches the negative of the battery.

Now connect the buzzer with the black wire in the remaining hole in the block and the red wire tucked under the elastic band on the positive end of the battery.

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This picture shows two paper fasteners used to hold down the buzzer on the top of the block but an elastic band can be used instead - double it around so that it catches on the plastic ‘lugs’ sticking out from the body of the buzzer. This will hold it securely.

See the following pages for Morse Code examples...

Click to go to the page

Electricity 1

This page shows how a paper clip can be used as a switch and it has a copy of the Morse code with some examples.

World War 1

Have a close look at how the paper fastener has been bent into a suitable shape for a switch in the pictures and video clip on this page.


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