Step 1: Parts
LM339 quad comparator
3 x 1k smd resistor (no bigger than 1206)
3 x 470 ohm smd resistor (no bigger than 1206)
2 x 1uf capacitor (no bigger than 1206). I suggest yo buy this somewhere other than Jameco, since the minimum order quantity is huge for this component. I just used through-hole capacitors for this one instead
2 x 0.22uf capacitor (no bigger than 1206)
2 x 0.1uf capacitor (no bigger than 1206)
1 x smd prototyping board for SMD 16-pin ICs
1 x audio connector, your choice
1 x 9V battery connector
3 x 500K potentiometers, or fixed resistors of many different values (CANNOT just use 470K resistors and get a "balanced" output)
3 x wires
3 x LEDs size and power are your choice. The maximum current from the LM339 is just about 16mA, so you cant use high power LEDs. I suggest 3mm LEDs, blue for low, red for mid, and yellow for high, but that is yor decision. The one in the pictures used one red 3mm led, and SMD blue and yellow LEDs. The SMD LEDs were 5050, so I couldn't fit the red one in.
*optional* you can add headers for an external display. The output of the LM339 will drive PNP type transistors if connected directly to the base.
Step 2: The Schematic
The potentiometers can either be soldered in a "bridge" over other components, or you can drill through the board and mount them on the other side.
If using resistors, you will attach them in step 5.
Step 3: Soldering Tips
2) Use an iron below 30W. Anything higher can destroy the components.
3) After soldering each pin, touch the LM339 chip. If it is too hot to touch, stop soldering for a few miniutes, then continue. You may have to stop multiple times.
4) Use play-doh, adhesive poster putty, silly putty, or even glue to hold the components that you're soldering. DO NOT attempt to hold them with your fingers while soldering, you WILL be burned by even the lowest powered of irons.
5) Solder the SMD stuff first, and the pots/resistors, LEDs, and wires next.
Step 4: Audio and Power
You can add a switch for the 9v battery, though it is not included in the schematic. The red, blue, and yellow wires are labeled for their connection to the protoboard circuit.
"signal", "audio -", and "audio grd" are the same.
DO NOT attach signal to power ground. This will short out your input source.
Step 5: Test It
The LEDs should blink on a loud note, but not be almost constantly on. The bass LED will usually be much more sensitive than the high and mid LEDs, and the mid more sensitive than the high. This is because a low note is usually more powerful, and the capacitors allow more power to pass through.
Step 6: Rock Out!
By soldering 2 component leads to the top pads of the board and bending them over the back, you can make the worlds coolest lapel pin.
-project Inspired by Colin Cunninghams color organ and SMD circuit videos, though no content from them was used. The circuit was compleatley designed by me.