. It automates the complex resistor calculations required to set specific reference voltages and LED brightness levels. Key Features & Capabilities Automatic Resistor Scaling : It calculates the values for resistors cap R sub 1 cap R sub 2 to set the full-scale voltage ( cap V sub r e f end-sub ) and the current for the LEDs. LED Current Control
This determines the current flowing through each LED. The LM3915 regulates this internally to about 10 times the current coming out of the Reference Output pin (Pin 7). lm3915 calculator updated
$$R1 = \frac1.25VI_LED$$
Resistors have tolerance errors. Instead of fixed resistors for R2, use a . 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. LED Current Control This determines the current flowing
Warning: Avoid tools that don't mention "logarithmic" or "3dB/step." Some sites mistakenly link to the LM3914 linear calculator. Instead of fixed resistors for R2, use a
Unlike its sibling the (which is linear) or the LM3916 (which mimics a VU meter), the LM3915 has a 3dB/step logarithmic response.