1. Decibel Level Detector Project Chris Lombardo IME 458

2. Produce a decibel level detector with a range of 0-50 decibels Use a LM3915 integrated chip to drive a series of ten groups of LEDs Objective

4. Circuit Diagram

5. BOM CountRefValueDescriptionSizePart #MFR 1R110kResistor Std 6R2, R3, R5, R7, R8, R10 100kResistor Std 1R447kResistor Std 1R61kResistor Std 1R956kResistor Std 1R114.7kResistor Std 2R12,R14100Resistor Std 1R13330kResistor Std 1R15220kResistor Std 1R1610Resistor Std 2R17, R19390Resistor Std 1R1822kResistor Std 1P110kLog Potentiometer Std 3C1, C4, C8330nFCapacitor 1C247uF/10VCapacitor 2C3, C9100uF/10VCapacitor 1C5100nFCapacitor 1C6470uF/16VCapacitor 1C710uF/16VCapacitor 1IC1 MC33172P 1IC2 15V Reg Voltage Regulator LM2931AZ5TXS 20LED Red LEDS MV8191Everlight 1Mic Electret microphone CEM-C9745JAD462P2.54R Challenge Electronics 1Bat 9V Battery Std 1Switch SPST switch 2FA5373TABS CARLING TECHNOLOGIES

6. Project Description Omnidirectional electret microphone serving as the input Two amplifiers with the first amplifying the signal and the second serving as a rectifier driver The Q2 transistor charges capacitor C8 and then discharges it across R13 to make a peak detector

7. The Q3 transistor changes the sensitivity of the LM3915 chip giving the system an extra 20db of range The main component of the system is the LM3915 itself which controls the currents through the LEDs while also measuring the input voltage line SIG logarithmically with a range of 0-50db Description Continued

8. After completing this project I have a fully functioning sound level reader with a range between 0-50db with steps of roughly 5db between each LED Overall success but a board with dual LM3915s would be more useful. Conclusion