comming up with a sound level indicator here i am explaining the steps to make the same with some faults which i did but you need not to suffer during the project.

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Step 1: Schematic for the Project

This project uses a LM3915 driver IC. function of this IC is to read the amplitude of input amplified signal and operate led based on reading(for better understand of output refer video). this is based on the concept that as the amplitude of the sound signal increases the no. of led swittched ON in the array increases and vice versa(as shown in fig.)Input signals(as shown in fig) can be introduced in circuit by mike, or by phone as in this video.

Step 2: Increasing Voice Sensitivity.

sensitivity with respect to voice on output can be increased and decreased by this component called preset(variable resistor) by rotating the minus hole clockwise and anticlockwise. other component used in this circuit are general resistor, switch,capacitor and a power source. specifications for the power source-(9-25)volt. The soung signal which we are inputiing are inthe form of waveforms .

Step 3: Making a Pcb

start making a pcb by mounting the ic in the ic base(recommended as during the testing ic can burn due to technical faults then it will prevent from desholdering of complete ic as ic from ic base can be easily removed by gentle force).

now make connections according to schematic diagram. here i will recommend ribon cable for making connections from ic base to led's for the sake of ease.

Step 4: Problem Encountering

you will encounter most of the problem during introducing the input to the what i have cut my old earphones(in not working condition) to input signal in can also use a small mike shown in fig. benefit of this component is that you can also make output for your voice, clapping hand, scolding mom etc.

Step 5: Inputing Signal Using Phone(music)

for this you need to cut your old earphones after cutting you will get 6 wires

1.right earphones

2.right ground

3.left earphones

4.left ground


6.supporting cable

of different colours now how you will get the correct wire??

this can be obtained using a muiltimeter. the jack of the earphones are divided into 4 cuts. 1st cut is for left audio then 2nd for right followed by cut for ground and at last for mike. now strip the wire end this can be easily done by buring it using matchstick and rubbing using a sand paper. now take the multimeter set it to the continuity and put one probe on the 1st cut and another probe on the any wire and change hte wire till ypou get the beep sound from multimeter. Now at input join the left and right audio cable and input the signal. secondly join the left and right ground connect it with circuit ground. nopte that it is mandate to connect both ground as without it we will loose ha;f ogf the input signal.

Step 6: For Betterment

use a dual earphone jack so that you can also listen to the music beat and encounter the syncronization of the music beat with the output. in this video i have used an old type dual audio jack.

Step 7: Output

connect the power source and switch on the circuit and play the music.

for better observation play in dark.

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    2 Discussions


    2 years ago

    We live near a firing range, I'd be interested to use one of these and see what it says :)