This is a quick how-to guide for making a stereo VU meter using the LM3915/LM3916. The LM 3916 is an integrated circuit (IC) that takes analog voltage levels and drives 10 LEDs, LCDs, or vacuum fluorescent displays to represent digital voltage levels just like a VU meter.
A LM3916 IC will take one signal source. Thus if you want to display a stereo representation of your audio, you must install 2 LM3916 ICs.
Click to above to enlarge
This is the schematics of the circuit I built. Keep in mind what I said earlier about mono, and stereo.
The 2.2 uF Tantalum Capacitor is only needed if your wires from the IC to the LEDs are longer than 6 inches. Although the specs for the LM3916 say you can use any voltage from 3 V to 20 V, I suggest using at least 12 V to power your circuit.
So before soldering everything together, letís just test the circuit on a protoboard. First letís get everything ready. The following items are what we need for this project:
10 LEDs of your choice (5mm or 3mm doesnít matter) I chose 2 green, 3 yellow, 3 red, and 2 blue
One 1.2 KOhms resistor
2.2 uF Tantalum capacitor (optional)
soldering iron and various cutters
Ok, letís start with the assembly.
After getting all the components ready, it is time to start prototyping. First to be placed onto the protoboard is the most important piece, the LM3916 IC.
Then put everything else together. Ah, noticed for this prototype I used 10 5mm blue LEDs. Hurray, the prototype worked. I hope yours did, too.
Now itís time to design the permanent circuit. Here is where you can get creative, you can arrange them the way you want them, and find creative ways to put it all together. Here is how I did mine.
I used DUBOX connectors (those blue things you see in the picture). By using those connectors I could just use the wires you see in the next picture (hanging from the power supply) to change LED color or simply making longer or shorter wires to reach my LEDs.