I graduated from the University of Advancing Technology in April 2008 and I wanted to do something to stand out a little…
I had an idea for a while to build a VU meter into a tie or T-Shirt. I decided to kill two birds with one stone by building the VU meter into my graduation gown. The end result was 10 super bright blue leds lined up the front of the gown. There was a small electret microphone clipped at the top of the gown facing my mouth. When I spoke, the leds would light up from the bottom to the top depending on the volume of my voice. The lights would also react to ambient noise if it was loud enough. I added a potentiometer to control the sensitivity of the microphone in case any tweaks were needed on the spot.
Here you can see the 10 leds lined up the front of the gown.
This is the (very messy) protoboard layout of the circuit while I was designing it. My breadboarded projects always look like a mangled mess of wires.
Top view of the PCB. I didn’t have any etching chemicals and this just seemed easier at the time. I’ve never etched a board before and I was running really short on time before graduation day.
Bottom view of the PCB. As you can see it is much more irritating when the PCB isn’t pre fabricated. I had to solder all these wires on there without shorting anything out.
The PCB was stuck in a small enclosure I made from cardboard and duct tape. I then used extra duct tape to make a sort of sash to wear the box under my arm at my side. I was originally going to fasten it to the inside front of the gown somehow, but this created a large, obvious blob under my neck. This worked really well and didn’t get in my way as much as you would imagine.
Here’s a video of me testing it out for the first time. At the time all I had was my cell phone so that explains the grainy video. You can still clearly see the lights reacting to the noise though.
I had a few requests for schematics, so I drew them up in Eagle. I had been meaning to do this anyway, but never got around to it. Thanks for the motivation! One important note about the OpAmp circuit: IGNORE THE PIN NUMBERS. I just worked with whatever opAmp symbol I could find so those pin numbers are not correct. What IS correct are the (+ – VCC VSS) signs on the symbol. You will also note that the LM324N is a QUAP op amp but I only included one opAmp symbol. This is because all of the other pins were left unconnected anyway. I just used what I could find. Based on the diagram, you shouldn’t have much trouble duplicating the circuit with another opAmp as long as the chip you use works with these power supply voltages and input source voltages. Check the datasheet if you are unsure.
All in all this project was a success. Everyone loved it. People would walk up to me and just make noise to see the gown react. During the ceremony my school played a video they made complete with blasting techno music. The lights danced to the beat of the music and it looked awesome. I wish I could have been standing up for that because it was really cool to see.
what chip did you use, got any schematics or links to schematics? Very cool.
Thanks for the kind words! I’m glad someone is interested. I used an LM3914N for the main voltage meter circuit. You can actually read the number right off the chip in the third pic above. For an amplifier I used an LM324N quad op amp chip. I really only used one of the op amps in the chip so it was overkill, but I couldn’t find anything else locally that I could get to work with a small voltage source and power supply. I do have schematics but they are hand written. I’ll see if I can get them scanned or maybe I’ll open up Eagle CAD and whip something up.
Very cool project! I too would be interested in the schematic….hand written or otherwise.
Ok I threw together the schematic in Eagle. I hope I didn’t miss anything. If you have any questions post em and I’ll try to answer them as best as I can. I separated the whole circuit out into the three main components to try to make it easier to understand. I found it easier to manage in smaller parts rather than one large circuit. Here’s the link to the schematics:
http://i83.photobucket.com/albums/j298/ricosgoo/FullSchematic.jpg
I’ll try to embed it in the page above but I’m not sure I’ll be able too. Maybe I’ll just remove one of the other photos and replace it with this.
sweet, thanks. fyi, you can embed images with ! points like: ! myimagelink ! (without the spaces)
Oh, one important note about the OpAmp circuit: IGNORE THE PIN NUMBERS. I just worked with whatever opAmp symbol I could find so those pin numbers are not correct. What IS correct are the (+ – ) symbols on the symbol. You will also note that the LM324N is a QUAP op amp but I only included one opAmp signal. This is because all of the other pins were left unconnected anyway. I just used what I could find. Based on the diagram, you shouldn’t have much trouble duplicating the circuit with another opAmp as long as the chip you use works with these power supply voltages and input source voltages. Check the datasheet if you are unsure.
Way cool!
Haha, this is great! Unfortunately for my school, the most creativity we saw on graduation day was from decorated graduation caps. Nothing like this!
Dan,
Graduation Stoles
Someone recently messaged me with the question, “What did you use so that you didn’t have wires going everywhere to link the LEDs on the gown to the control box?” It was actually pretty simple. You can see on either side of the zipper there are large flaps of cloth. I just used black stranded wire and hid them behind one of those flaps. I wrapped all the strands together with black electrical tape to keep them bunched together neatly. The flap was big enough to hide all the wiring from the front. If someone had looked closely at the side of the flap they would have been able to see some wires, but it really wasn’t a big deal.
I see a lot more on your PCB than what you have listed in the schematic. Anything important? I myself am trying something similar for graduation. Sadly I don’t have access to a LM3914 since all our electronics stores are lame around here :P so I am trying to mimic it with comparators but there have been problems. Are you familiar with the 3915 chip and would it work in its stead or do you need the linear workings of the 3914?
(complete instructions)