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Pushbutton Switch Schematic Circuit Diagram

Pushbutton-Operated Switch Circuit Initialization

This circuit functions akin to a two-position switch, but its operation relies on a pushbutton. Upon power application, the circuit starts in an initial state. The bases of transistors T1 and T2 are at a positive supply potential, and the base of T3 is at ground potential. All transistors are in a cutoff state. The alternate pushbutton contact is grounded. Consequently, no current passes through the relay coil, and the status LED remains unlit.

Pushbutton Switch Schematic Circuit Diagram

Pushbutton-Driven Toggle Operation

When the pushbutton is pressed, T2 and, after a slight delay due to the RC network, T3 become active. T3’s collector reaches nearly ground potential, allowing current to flow through the relay coil and lighting up the function LED. T1 can also activate in this state. This configuration stabilizes because ground potential can reach T2’s base through R1, ensuring no change occurs when the pushbutton is released. C1 charges through R3, establishing a positive potential at the pushbutton. Upon the next push, the pushbutton connects a positive potential to T2’s base, reverting the circuit back to its initial state.

Independent Operation with Low Voltage Demand

A similar effect can be achieved with a thyristor circuit; indeed, T2 and T3 resemble a thyristor. However, this presented circuit is remarkably independent of the voltage and current requirements of the connected load. It’s essential for the relay coil to be compatible with the supply voltage (ranging from 5V to 12V) and not exceed 250 mA to prevent damage to T3. In our lab prototype, we recorded a current consumption of 70 mA in the ‘on’ state and less than 0.1 mA in the ‘off’ state.

Understanding Voltage in Electrical Circuits

Voltage acts as the force from an electrical circuit’s power source, driving charged electrons (current) through a conductive loop, enabling them to perform tasks such as illuminating lights. In essence, voltage represents the pressure in electrical systems and is measured in volts (V).

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