Follow these steps to calculate the exact resistor values for your specific project requirements. Step 1: Establish Your Desired LED Current
To find R2, we rearrange the formula:
R1=12.5ILEDcap R sub 1 equals the fraction with numerator 12.5 and denominator cap I sub cap L cap E cap D end-sub end-fraction 4. Step-by-Step Practical Calculation Example lm3915 calculator updated
R1=12.5ILEDcap R sub 1 equals the fraction with numerator 12.5 and denominator cap I sub LED end-sub end-fraction
Proper current sourcing (usually 10x the reference current). Follow these steps to calculate the exact resistor
Let’s calculate components for a standard 12V VU meter with 10mA LED current and a maximum VRHIcap V sub cap R cap H cap I end-sub
Connecting Pin 9 to V+ creates a bar graph. Leaving it open creates a single dot, which consumes less power. Power Dissipation: The LM3915 can get hot. Ensure VLEDcap V sub cap L cap E cap D end-sub is not excessively higher than the LED forward voltage ( VFcap V sub cap F Let’s calculate components for a standard 12V VU
VREF1.25=1+R2R1the fraction with numerator cap V sub cap R cap E cap F end-sub and denominator 1.25 end-fraction equals 1 plus the fraction with numerator cap R sub 2 and denominator cap R sub 1 end-fraction
Note: To fine-tune the range, replace R2 with a potentiometer or a trimmer resistor.
However, traditional, rigid formulas often lead to incorrect LED intensity or improper scaling. This article provides an to the LM3915, including refined calculation formulas for 2026, component selection best practices, and a guide to using the LM3915 calculator tool for rapid design. 1. What is the LM3915 and Why Updated Calculations?
The bottom of the internal resistor ladder. Usually tied to ground (