Telegraph

Overview

Alexander Graham Bell knew about the telegraph. It had been patented by Samuel Morse in 1837. Before Bell patented the telephone he experimented with telegraph circuits. In this exploration students build  a simple telegraph system by making an electromagnet, sounder and switch. Students develop a sense of how technology can be modified and adjusted to be the most efficient tool possible.

Preparing Materials

Students can make a telegraph in a variety of ways. This method requires the fewest tools and has the least materials of most models one can find.  It is easily built in a short time frame and has no sharp steel edges.

• Foam food trays

• Glue gun

• Scissors

• pie tin (aluminum)

• two machine screws (8-32 or 6-32, 2-3 inches long and 2 screws 1/2" long)

• 7 nuts to match

• enameled wire

• batteries (2 "C" or "D" cells) 

• Miscellaneous wire

Exploration

The story of the invention and patent of the telegraph is an interesting LA STEM story that will be added at a later time. For now, it is important to say that the inventor, Samuel Morse, was not a professional scientist or engineer, he was an artist with an idea.  Encourage students who will be doing this model building that they can be successful, as was Morse, with patience, persistence and with careful attention to detail.

Step 1. Cut the foam base

Use a scissors to cut a piece of foam tray about 13 x 5 cm. 

Step 2. Make an Electromagnet

A long machine screw of most any size and thread will work. You will need two nuts. Place one nut on the end of the screw so it will form the end of the copper windings. Cover the threads with tape so the copper wire will not be scratched and short out.  This electromagnet had about 125 wraps. You can have a bit more or less and it would not make a difference.  Generally, the neater the wraps and the more wraps, the stronger the electromagnet.

Step 3. Attach the Electromagnet to the Board

Step 4.  Cut and bend a piece of aluminum pie plate. Look at the next picture as well. You can use a punch to make a hole in the short angle of the plate.

Step 5. You may want to continue looking at pictures to see how to make the bend in the pie plate. Attach the short angle to the base as shown.

Step 6.  Add a washer to the top plate.  Because aluminum will not be attracted to a magnetic field, attach an iron washer to the top of the flap.  The washer should be just above the head of the screw and there should be a small gap between the screw head and the pie tin.

Here is the completed system: