Metal Film Resistor: November 2013

A few years ago I designed an awesome circuit.

Awesome:

My definition of awesome:

cheap
easy
practical
awesome

I was searching for a way to build a VU meter. Before microcontrollers, all my projects were audio based: I just wanted to find ways to make my desk/room/life awesome. I built amplifiers, blinking lights, speakers, etc. I wanted to build a VU meter, so I fould the LM3916/3915/3914 family.

LM3916

I heard/read that this chip works logarithmically. That means that each LED that lights up is one decibel.

Of course, like all the other chips in this family, it runs on 6v or higher and has the option of dot display (one dot) or bar display (bar VU).

LM3915/3914

I think these two are almost the same. This chip works linear, so it isn't great for measuring decibels, which is logarithmic. It runs on 6v or higher, and has the dot display or bar display option.

So anyways, I built a few of these VU meters, the first ones being failures.

I don't even have pictures of it: It was my first attempt at double sided PCB and I failed pretty badly. It was operated by a microphone, ran on 9v, and had an LM386 as an amplifier.

In those days, I learned that the less components you use, the better the circuit works (I was guessing and checking). For example, I built an LM386 amp that week and I took away a bunch of capacitors and resistors and the end product was amazingly better than the original schematic.

So, I used that philosophy to build this. I ended up with a USB powered VU meter with only a chip and 10 LEDs as necessary parts. Everything else is optional.