Materials Needed

telegraph assemble from project # 3

hookup wire


You can use the telegraph you made the first time in project 4 because your telegraph station can easily be adapted to work as a buzzer. To complete the construction of the buzzer take your hookup wire and cut about 8''. Remove the insulation from both ends and right in the middle of the wire remove about 1 1\2'' of insulation because this will be the part that will touch the sheet metal. In order to touch the sheet metal you need to make a dend were you have remove the insulation so it will look like the letter ,m,. Now you can connect one end of the wire to hole 6 and the other end bring it over the sheet metal and connect it to hole 7. After you finish adjust it so the part that you made it as the letter m will touch the sheet netal. Remove the magnet wire in hole 1 and connect it to hole 6. Cut another piece of hookup wire about 7 1\2" to connect it in hole 5 and hole 1. When a piece of wire is use to make cinnections from one place to another then their are called wire connection. Now to complete the circuit press the key.

What Is Happening

When you press the key the electromagnet is energized. This action pulls the sheet metal strip down, which consequently breaks contact with the hook wire around the sheet metal, causing current to be interrupted to the electromagnet which releases the srtip. Electrical contact is restored, pilling the strip down again etc. The rate at which this happens, which determines the pitch of the tone you hear, depends on how heavy the strip is, and how easy once moved, it will spring back to its original position. A variation of the buzzer is the door bell, which gives a continous clanging ding-ding-ding-ding. To accomplish this all you need to do is extend the sheet beyond the electromagnet, place a little weight on the end, and mount something next to it that will clang when hit. Do not forget that if one battery holder produces electromagnet that is weak try to hook up two battery holders in series.