This Instructable will teach you how to make an inexpensive wearable safety alarm necklace. For me, living in NYC means that my nightly commute between the train and my apartment is often fraught with concern for my safety.
I designed a wearable technology piece that sets off an alarm when the wearer triggers the alarm with a copper ring, but any metallic/conductive trigger would work.
Piezo Buzzer (Radio Shack)
Copper tube (that fits on your finger)
Solder (would be helpful)
Step 1: Connect Battery to Speaker
Of course, you'll want to test your battery first, just connect the negative (black) leg of the battery to the speaker and the positive leg (red) of the speaker to the battery to make sure everything is in order.
Then you'll want to connect the Piezo Buzzer to the battery. I soldered the two legs together, but if you don't want to solder, you can wrap the wires together with copper tape.
Step 2: Make your necklace centerpience
I used a brass fitting to be the centerpiece of my necklace, but really you could use anything you'd like- gems, weaving, trinkets, tiny dinosaurs, etc.
I wrapped the to ends with white electrical tape to prevent my circuit from short circuiting. You should do the same if your centerpiece is made of metal. Copper tape will be added to the sides of the necklace, and if the tape wasn't there, the alarm would go off constantly. The brass ring you'll wear, and touch to the necklace will close the circuit.
Step 3: Connecting the necklace to alarm and battery
This is the easy part. Just thread conductive thread through the two ends of the necklace center piece and bring it to the two exposed positive wires from the battery and speaker respectively.
I wore BEACON with a cape and let the battery and speaker rest in the hood of my cape for two reasons: 1. I wanted the speaker to face outward and 2. I wanted the hood to support the weight.
In the images above, I threaded conductive thread through the copper tape, and also soldered it for extra connection.
Step 4: Wrapping the conductive thread
I wrapped the conductive thread with wool to take some of the necklace's weight off the conductive thread. It changes nothing about the functionality of the necklace.
Step 5: Test the connection.
Essentially all you're doing with the brass ring is closing the circuit for the necklace. When you touch the ring to the centerpiece of the necklace, you're allowing electrons to flow between the two pieces of copper tape to trigger the alarm - pretty simple huh!?
If it doesn't work, most likely the ring isn't touching the two pieces of copper tape properly.
Step 6: Decorate your necklace (if you wish)
I liked the bare look of the necklace, but I decided to see what it would look like with paper decorations, so added the black and blue paper with hot glue.
I also added fairy lights to my necklace. The fairy lights increase the visibility of the connection point in the case that you need to trigger the alarm in deep darkness. This might be something you'd want to consider.