LM3915 Audio Level Indicator

Engineering Principle: The LM3915 is a 10-LED strip driver chip, similar in function to the LM3914. The LM3915 lights up the LEDs one by one according to the input voltage. In this circuit, the LM358 amplifies the audio signal, and the LM3915 provides a direct display of the audio signal, allowing users to intuitively experience the impact of the audio. Function: Used to enhance multimedia equipment such as audio systems (audio companions). It can also be used to measure the amplitude of analog signals. The LM3915 (logarithmic indicator) can be replaced with an LM3914 (linear indicator) to create a voltmeter. Operating Conditions: The audio input needs to be connected to a preamplifier (or a signal can be provided via a header pin; before the power amplifier, it can be directly output from the computer/mobile phone audio port; if too many LEDs need to be lit, the potentiometer can be adjusted). The power supply is 5V DC, positive inside and negative outside (or powered via a header pin). A 1-to-2 audio splitter and a USB to DC005 converter can be used to directly power and provide signals to the circuit via a computer. Test parameters: Testing showed that the current draw was only 40mA when all LEDs were lit and only 2mA when all LEDs were off, demonstrating extremely low power consumption. It also did not interfere with the original circuitry and could be modified for use on any multimedia device with a 3.5mm plug. The circuit includes four screw holes and pin headers for easy mounting (screws or magnets can be used to attach it to other devices). It is also easy to embed into other DIY projects (such as speakers). The LEDs are 2*5*7 square, and the LED colors can be selected as needed. The lighting sequence is LED1 to LED10, and LED11 to LED20.
Demo video address: [link to demo video]