pcb How to use the same switch to control LED and vary resistance

A 4-position slide switch is utilized to activate different colored LEDs based on its position. Additionally, it is required to adjust the output frequency of a 555 timer operating in astable mode to drive a piezo buzzer. The challenge is to control both the LEDs and the resistance values using the same switch position, enabling the selection of different LEDs while simultaneously varying the resistance and, consequently, the frequency of the 555 timer.

To achieve this functionality, a circuit can be designed incorporating a 4-position slide switch that connects to both the LEDs and the 555 timer. Each position of the switch will be linked to a unique combination of resistors and LEDs.

The circuit can include four resistors, each corresponding to a specific LED color and connected to the output of the slide switch. When the switch is positioned to select a particular resistor, it will alter the resistance value in the timing circuit of the 555 timer, thereby changing the frequency of the output signal.

The 555 timer, configured in astable mode, will generate a square wave output whose frequency is determined by the formula:

\[ f = \frac{1.44}{(R_A + 2R_B)C} \]

where \( R_A \) and \( R_B \) are the resistances connected to the timing capacitor \( C \). By selecting different resistors through the slide switch, the frequency can be varied, which will, in turn, modulate the pitch of the sound produced by the piezo buzzer.

To ensure that only one LED lights up at a time, the circuit can employ a common cathode configuration where the anodes of the LEDs are connected to the respective switch outputs. This setup allows for the selection of a specific LED based on the position of the switch, while the corresponding resistor adjusts the timer frequency.

In summary, this design effectively uses a single 4-position slide switch to control both the illumination of different colored LEDs and the frequency output of a 555 timer, thus driving a piezo buzzer with varying tones based on the selected switch position.I have a 4 position slide switch according to the position of the slide switch, I should turn on different colored LEDs and also vary the output frequency of 555 timer in astable mode and drive a piezo buzzer. Problem : I cant use the same switch to control LEDs and vary the resistor values. How to achieve this that is chang ing the switch position should select different LEDs and also vary the resistance, thus varying the frequency of 555 timer. 🔗 External reference