The Telegraph is one of the first applications of the electromagnet. In this project contruiremos a telegraphic manipulator and a buzzer.

History of the telegraph 

The first electrical equipment for telegraphic transmission were invented by the American Samuel F.B. Morse in 1836, and the following year by the English physicist Charles Wheatstone in collaboration with engineer Sir William F. Cooke. The basic code, call Morse code, transmitted messages by means of electrical impulses that circulated around an only cable. The Morse set, who issued the first public telegram in 1844, had form of electrical commutator. By means of the pressure of the fingers, it allowed the passage of the current during a certain lapse and next it annulled it. Original the Morse receiver electromagnetically had a controlled leader that drew outlines in a paper tape that turned on a cylinder. The outlines had a dependent length of the duration of the electrical current that circulated around cables of the electromagnet and presented the aspect of points and rays.

Materials for this project (shown down) can be obtained of our Kit de Telégrafo.

  • Wood base
  • Enameled copper wire
  • La'mainas of metal for manipulator and buzzer
  • Nails and screws
  • Portapilas



1. - The base of the telegraph of this kit comes with some pilot holes. The diagrams of the image of the side are used to mark the holes with letters. This will help us in the next steps where it is needed to connect the wires. The hole marked with N is a hole that happens until the other side of the wood.


2. - We insert the great nail in hole N. The nail does not have to excel of the part of back of the board. Then, when installing the buzzer in the form of Z, will have to be to 2mm on the nail. This nail will be the nucleus of the electromagnet.



3. - We surround something of sticky tape on the nail. This tape will act as an insulator and avoids that the wire touches the nail. Although the wire has an enamel (of there its name) is used sticky tape as additional precaution.

4. - The spool is taken from enameled wire no. 28 AWG. They are left as 12 cm of the beginning of the wire and soon become involved around the nail some 400 to 500 returns. Finally other 12 cm are left when finalizing. Alabre is cut.

5. - The ends of the enameled wire can be twisted together to avoid that it develops. Sticky or insulating tape becomes involved again to protect the wire. Now we must take the ends of the enameled wire and with the help of a sandpaper we cleared the enamel to about 3 cm of the ends of the enameled wire. With this already we have a coil.


6. - It inserts a screw in hole A.


7. - To surround and to assure the wire in the screw in position A. also connect the black wire of portapilas to the same screw. The bare part of the wire of portapilas must be underneath the head of the screw. To screw the screw with force.

8. - It inserts a screw in hole C and connects the other end of the coil to screw C.


9. - We pass a screw in the hole of the small metal lamina and soon we put it in hole B, so that the other end is on screw C, but without touching it.

10. - In this point the circuit this ready one, can verify installing the batteries and pressing the broad strip of on screw C. Right away the great nail it must become a magnet.

11. - Now the buzzer in the form of Z settles placing a screw by the hole in one of its ends and inserting in hole Z. this strip of metal is placed so that the longest part is on the nail, but without touching it. The distance between the head of the nail and the metal strip must be of about 3 millimetres.
12. - In this point the buzzer already is ready to try. The small metal strip is pressed (that now we will call manipulator) and the longer metal strip must touch to the head of the nail producing a click.
The photo alongside shows the complete telegraph, as well as the parts of the electromagnetism kit.

How to make a buzzer

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