Lm3915 Calculator Updated May 2026

Some LM3915 circuits include a peak hold capacitor. The updated calculator includes a timing tab. Enter your desired hold time (e.g., 0.5 seconds), and it calculates the required capacitor value for pin 12.

One of the best features of the LM3915 is daisy-chaining.

import math
def calculate_components(Vin, Vref, gain):
    """
    Calculate the required components for the LM3915 circuit.
Args:
        Vin (float): Input voltage.
        Vref (float): Reference voltage.
        gain (int): Gain of the amplifier.
Returns:
        dict: A dictionary containing the calculated component values.
    """
    # Calculate R1 and R2 for the voltage divider
    R1 = 1e3  # 1 kΩ
    R2 = (Vref / Vin) * R1
# Calculate the value of R_G for the gain
    R_G = 1e3 / gain  # 1 kΩ / gain
# Calculate the value of R_OUT for the output
    R_OUT = 1e3  # 1 kΩ ( typical value )
return 
        "R1": R1,
        "R2": R2,
        "R_G": R_G,
        "R_OUT": R_OUT,
def main():
    Vin = float(input("Enter the input voltage (Vin): "))
    Vref = float(input("Enter the reference voltage (Vref): "))
    gain = int(input("Enter the gain of the amplifier: "))
components = calculate_components(Vin, Vref, gain)
print("Calculated Component Values:")
    print(f"R1: components['R1']:.2f Ω")
    print(f"R2: components['R2']:.2f Ω")
    print(f"R_G: components['R_G']:.2f Ω")
    print(f"R_OUT: components['R_OUT']:.2f Ω")
if __name__ == "__main__":
    main()

Major blocks:

Title: LM3915 Calculator – Major Update

Body:

I've just pushed a significant update to the LM3915 Calculator. For those unfamiliar, it's a web-based tool to help you configure the LM3915 dot/bar display driver without digging through the datasheet every time.

What’s new in this update:

Use cases:

Check it out here: [Insert URL]

Feedback welcome – let me know if you'd like to see logarithmic scaling options or a parts list generator next.

Resistors have tolerance errors. Instead of fixed resistors for R2, use a 10k or 20k trimmer potentiometer. Connect the wiper to the Ref Adj pin and one leg to Ground. This allows you to precisely calibrate the "full scale" of your display without soldering new parts. lm3915 calculator updated