Simple Audio VU meter(iPod Output and a speaker out plug)

PART NO. 2182670

This is a fun kit that utilizes two 3914 chips to display the dB of your music on a 20 led bar-graph display. This kit is very adaptableand can be incorporated into another project, for example making a tower of lights, then hooking the circuit up to your tower and thenyou have a really cool LED dB meter tower in your living room or tech cave. The speakers that are connected to the audio out on thecircuit should be powered or you will take away a lot of signal from your led VU meter resulting in a dull display that only flickers 3 or 4LEDs on and off.

Time Required: 1 hour depending on experience

Experience Level: Intermediate

Required tools and parts:

Soldering Iron and solderWireWire cutters(or scissors/knife)

Bill of Materials:

Qty Jameco SKU Component Name

2 300003 LM3914N 10 2157159 1k Ohm resistor10 330431 1uF Capacitor 1 255522 10K Potentiometer2 697469 10 segment bar display1 216427 9V battery clip2 2095437 3.5mm audio jack1 2120153 9V Battery1 228494 Stereo 3.5 mm Cable1 2157706 Breadboard

Step 1 - Placing the first components

Start off by placing the two 3194 chips onto your breadboard 4 pins apart and make sure the notches on the ICs are pointing thesame way (away from you) for convenience. Above or below the ICs, wherever there is space, push in your two 10 segment bargraph displays to make a 20 segment display. Then connect all of the positive LED pins from the bar graph display to the positive railon the breadboard. The positive wires should be on the side with some text printed on it (see picture). It is good to note that the 3914chips have a negative output.

Step 2 - Construct The Circuit

Using the schematic, connect the rest of your components to the circuit. When connecting the 3.5mm audio jacks you may beconfused because you don't know the pinout, it is quite simple, the connector that is closest to the opening on the jack is the GND(negative) the next pin in is audio right and the last pin is audio left. If you are still confused about the pinout just search "audio jackpinout" or look at its datasheet here -> http://www.jameco.com/Jameco/Products/ProdDS/2095437.pdf

(note that the audio jacks probably won't fit on breadboards so you will have to solder wires onto them)

Step 3 - Finishing up

Once you have fitted all your components, power up your project with a 9V battery and plug in your iPod to the input audio jack with amale to male 3.5mm cable and play a song on full volume for best results, you can adjust the display with the 10k variable resistor. Ifyou want to use the audio output jack, make sure to use powered speakers as normal headphones would drain the input to your VUmeter and make it boring. A simple powered speaker like the one in the picture would be perfect.