Semaphore Signal - Working model

Описание: In earlier days, Semaphore signals were used by indian railways.

Changing the angle of the arm gives different indications to the train driver.

They are being replaced with more advanced light signals.

We will build a model of this signal with the help of solenoid.

Solenoid is the generic term for a coil of wire used as an electromagnet.

I will take these two paper straws.

One straw is cut into three pieces.

These two pieces are connected together with cellotape to the main straw.

36 gauge coated copper wire is taken. 700 turns are made around this 6 cm long straw piece.

Both ends are tied together and coating removed with sandpaper.

Empty pen refill is cut and it is fixed to the main straw. We will prepare a signal arm from this small straw with the help of pin. When placed in the refill, it can rotate freely.

Let’s take this eraser. We will make two holes. One for the singal pole and one for the winding.

We will use this long needle. It is tied with thread and another end of thread attached to the signal arm.

This pin will arrest the movement of the arm downwards when the screw is inserted at the other end as counterweight.

Signal in this position indicates STOP for the train.

We will paint this paper strip and attach to the signal arm.

Now let us connect this battery holder to the solenoid. It has 4 AA batteries and can provide a potential difference of 6 volts.

When the circuit is complete, solenoid pulls the needle down as a magnetic field is generated.

The device creates a magnetic field from electric current and uses the magnetic field to create linear motion.

This will be active till current is flowing through the solenoid. Opening the circuit, releases the needle and signal returns back to horizontal STOP position.


Do try this at home.

Thank you.


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