Lm3915 Calculator May 2026

But for simplicity, designers often set ( V_\textRLO = V_\textLO ) and ( V_\textRHI = V_\textref ) (if ( V_\textref ) is scaled to match highest LED threshold). More practically: The LM3915’s internal divider has a ratio of ~1.25 dB per step in voltage terms, so the voltage at step n is:

RLO = 0 V (ground). RHI = 5.0 V (to reference). But now the highest LED triggers at ( V_\textin \approx 5.0 ) V peak? That’s far above 1.414 V. So we must attenuate input. LM3915 Calculator

Example: For 20 mA (typical bright LED), ( R_\textset = 12.5 / 0.02 = 625 \ \Omega ). Use 620 Ω standard. Design goal: Audio level meter for -30 dBV to +6 dBV (36 dB range, but LM3915 only does 30 dB, so compress or shift). Desired: LED1 = -30 dBV, LED10 = 0 dBV (30 dB span). Reference voltage = 5.0 V (from 12V supply). LED current = 15 mA. But for simplicity, designers often set ( V_\textRLO

Choose R1 = 1.2 kΩ. ( R2 = 1200 \times (5.0 / 1.25 - 1) = 1200 \times (4 - 1) = 3600 \ \Omega ) (3.6 kΩ). But now the highest LED triggers at ( V_\textin \approx 5

[ V_\textRLO = V_\textLO - \text(offset) \quad \textand \quad V_\textRHI = V_\textRLO + \fracV_\textHI - V_\textLO10^(9/10) ]

[ V_\textin,peak = \sqrt2 \times V_\textrms ]