How to Make a Dual Channel Vu Meter Using LM3914

In this post i will share on how to make a Dual Channel Vu meter using LM3914 IC. You can watch the video attached along with post for complete construction & working of the project or continue reading the post

Step 1: Components Required

For this project you only need few things

• 2 * LM3914
• 2 * IC Socket
• 2 * 1K Ohm
• 2 * 10K Trimmer
• 10 * Green LED
• 6 * Yellow LED
• 4 * Red LED
• 2 * 3.5mm Audio Jack
• 1 * DC Jack
• 1 * Switch

You can purchase the above components from the below affiliate links which would help me in lot of ways.

Amazon US

• LM3914 - https://amzn.to/2GO80Rp
• IC Socket - https://amzn.to/2GFxTBH
• 1K Ohm - https://amzn.to/2XOD359
• 10K Trimmer - https://amzn.to/2GFxTBH
• Green LED - https://amzn.to/2J6ikG5
• Yellow LED - https://amzn.to/2IONUbJ
• Red LED - https://amzn.to/2ZGbGfl
• 3.5mm Audio Jack - https://amzn.to/2DBWuXs
• DC Jack - https://amzn.to/2ZBKH4J
• Switch - https://amzn.to/2WbgXcL

Amazon India

• LM3914 - https://amzn.to/2GQuDVs
• IC Socket - https://amzn.to/2GPtzkD
• 1K Ohm - https://amzn.to/2GSjT97
• 10K Trimmer - https://amzn.to/2GO8nLN
• Green LED - https://amzn.to/2IZY5JP
• Yellow LED - https://amzn.to/2IZY5JP
• Red LED - https://amzn.to/2IZY5JP
• 3.5mm Audio Jack - https://amzn.to/2PA9Sjs
• DC Jack - https://amzn.to/2GOQk8k
• Switch - https://amzn.to/2J6ub6G

Ali Express

• LM3914 - http://s.click.aliexpress.com/e/cDDG9rag
• IC Socket - http://s.click.aliexpress.com/e/bpVtBMFA
• 1K Ohm - http://s.click.aliexpress.com/e/cHb4A04u
• 10K Trimmer - http://s.click.aliexpress.com/e/ch1nCdDA
• Green LED - http://s.click.aliexpress.com/e/bBvCHEys
• Yellow LED - http://s.click.aliexpress.com/e/bgwLt9b6
• Red LED - http://s.click.aliexpress.com/e/cgWIp7Qu
• 3.5mm Audio Jack - http://s.click.aliexpress.com/e/cZ3uwcZi
• DC Jack - http://s.click.aliexpress.com/e/7MNKXqo
• Switch - http://s.click.aliexpress.com/e/bX6ELUrq

Step 2: Circuit Diagram & PCB Fabrication

I designed my circuit using KICAD & tested the circuit on a breadboard & then designed my PCB layout & generated gerber & drill files for fabrication. For fabrication i used JLCPCB.com who provide very cheap & well built PCB's for just 2$(5 piece).

The circuit is constructed mainly around LM3914. For this project i had to use two LM3914 since i wanted separate analyzer for each channel i.e right & left. Each side analyzer is also provided with a trimmer, which can be used to calibrate. This circuit need 12 Volts 1Amp power for operation.

Step 3: Assembly & Testing

After receiving the board i mounted all the components according to their annotation.

After mounting all the components, i connected the circuit to a 12v power supply & then connected the audio input from a laptop & also connected one more input to a amplifier.

Note: After you power the circuit & connect it to a input there should not be any LED On. If there is any LED on then adjust the trimmer such all the LED's are OFF.

After all the connection & calibration are done, then the last thing left is playing a song.

Also Note: when you play a song & if your LED is not reacting then adjust the trimmer until you see the LED On.

Thank You for reading the post