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Insight - How Piano Switch works

Written By: 

Abhimanyu Mathur

The best place to find a piano switch is the nearest switchboard one can find. They are available in different sizes, shapes depending on the application and a number of switches can be placed on a single switch board. Installing and changing the switch is also quite easy and anyone having a basic know-how about electricity can use these switches.

How do piano switches handle high electrical voltage inputs? How are the interior configurations of the switch designed? Why they don’t stop in between their motion? Let’s find out some interesting information about these switches in this article 

Fig. 1: SPST Piano Switch
Shown above is a conventional SPST piano switch that works in ON-OFF state. The body of the switch is made from heat and fire resistant polymer material and can tolerate current shocks due to short circuit. It aids in protecting the user from cases of shock due to current leakages and fire incidents.
Fig. 2: Reverse of Switch showing Wire-Connecting Ports and Engraved Power Specificaitons
The reverse side of the switch has the wire connection ports and engraves details such as manufacturer information, technical specifications or certifications as shown above.
Fig. 3: Image Showing Structure and Parts of Ports
Depending on the specification of the switch, two or three ports can be provided on its back side where the wires are inserted and screwed. The ports have a metallic coat to prevent from corrosion and improve the longevity.

Internal Structure


Fig. 4: Image of Internals of Switch Actuator

The actuator of the switch when opened reveals the internal structure as shown above. We can see that the actuator has an assembly made up of metallic parts and spring.
As mentioned above there are two ports for holding the wires. One is permanently punched in the base as shown in the image above. The screw which is shown in the image above holds port 1. It is placed in the hole shown in the base.

Fig. 5: Spring-Loaded Lever System of Actuator

The actuator has a spring loaded lever system whose major task is to stabilize the position of the switch when it is in ON or OFF mode. The “click” sound made by the lever serves as an indication to the user that switch has been changed from on to off state or vice versa


Fig. 6: Image Showing ON State of Actuator

Switch Movements

Contact Movement: The image above shows the movement of the actuator. When the switch is in ON state, both the contacts touch each other thereby connecting the wires which are inserted in the ports and completing the circuit.  The spring loaded lever gets fixed to the lower layer of the switch and rest of the structure moves with respect to it in order to put the switch in ON and OFF manner.

Fig. 7: Image Showing Mechanism of Actuator in Closed State
Actuator Movement: The image above shows the off state of the switch when the upper section of spring loaded lever is placed to create distance between the two contacts.  In this state, the spring of the loaded lever is in a rest state and slots in the arm provide place for the lever to stay in this position for long.
Fig. 8: Image Showing Spring Position in Switch ON State
In the closed state, the arm moves to make the contacts touch each other, allowing current to flow from the switch to the corresponding device.
Fig. 9: Image Showing Spring Position in Switch OFF State


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