I created this piece so my students could quickly prototype wireless wearable project ideas. As you can see, the armband allows for various sensors to be snapped in and out. In fact, all electronic components are detachable making washing, maintenance and repair much easier. This armband is ideal for rapid prototyping and introducing students to creating wireless projects. In the case of my student's work, they received the sensor data into Max/MSP to develop realtime audio/visual feedback.
Step 1: Required Materials
For this piece, you will need the following:
- FLORA Microcontroller - https://www.adafruit.com/products/659
- Bluefruit EZ-Link - https://www.adafruit.com/products/1588
- Flora 9-DOF Accelerometer/Gyroscope/Magnetometer (Optional) - https://www.adafruit.com/products/2020
- Conductive Thread - https://www.adafruit.com/products/640
- Small Snaps - https://www.adafruit.com/products/1126
- Clear Nail Polish or Fray Check
- Crimp Beads - http://www.michaels.com/search?q=crimps
- Extra Fine Point Soldering Tip
- Fine Point Sharpie
- Large Notecards or Card Stock Paper
- .5" - 1" Thick Elastic
- Standard to Mini USB Cable
- Lithium Battery - https://www.adafruit.com/products/258
- Sewing Machine (Optional)
- Soldering Iron
- Sewing Needle
Step 2: Helpful Notes Before You Start
A note about the Bluefruit: The only I/O's you will need on the Bluefruit for this project are RX, TX, Vin and Ground.
A note about the Flora: I have had zero luck using the RX/TX I/O's on the Flora. For this project, I use a soft serial library to communicate between the Bluefruit and Flora. For this project, RX = D10 and TX = D9 on the Flora.
A note about sensors: I built this armband to use both Adafruit's Flora wearable sensors and any variable resistor sensors students wanted to use. As you can see in the prototype in Step 3, I built a snap in circle for the Flora wearable sensors, and I dedicated D6 and D12 for analogue input. If you want to use two variable resistors, you will have to add an extra snap to your power and ground lines as I have done. (See image above.)
A note about the electronics layout: The following steps explain how to make the armband in the image above. If I were to make this again, I would rotate all of the electronics 90 degrees so that the band was thinner. I found that this layout worked well on men but was a little bulky on women.
Step 3: Prototyping the Prototype
Build a prototype out of card stock:
Before you begin, I find it extremely helpful to lay all of this out on cardboard. If you just want to use my image above, you don't have to do this step, but I think it helps. Trace each of the major components, label any relevant I/O ports and cut out your shapes. Lay the shapes onto a large piece of card stock and draw lines connecting the corresponding I/O's.
Step 4: Adding Snaps and Sewing With Conductive Thread
Soldering snaps to your Flora and wearable sensors:
The nice thing about most wearable microcontrollers is that you can solder snaps directly onto them. Solder snaps onto both the Flora and onto any Flora wearable sensors you want to play with. If you haven't soldered snaps before, follow Adafruit's tutorial.
Making the Stencil:
Once you've soldered on your snaps, firmly press the Flora/sensors into a notecard until the studs push through and make holes. Use this notecard as your stencil. Lay the stencil onto your felt rectangle and with the fine point sharpie, mark where you will sew the other side of your snaps. Using your prototype as a model, make a dotted line branching out from each snap location. You will use this as a guide for sewing your conductive thread.
Sew the Conductive Thread:
If using a sewing machine, place the conductive thread in your bobbin compartment and regular thread in the top. Sew along the dotted lines leaving long threads on each side. Use the long threads on each side of the stitch to sew down your snaps. You will have to use an embroidery stitch to complete this. When you knot the ends of your conductive thread, don't cut the end right away. Conductive thread has a tendency to "un-knot," coat the knot with clear nail polish or Fray Check to harden the knot. Once it dries, cut the thread end close to the knot to avoid shorting with other knots. For more detail on machine sewing, check out Adafruit's tutorial.
If you do not have a sewing machine, you can hand stitch these lines. Just make sure you use the same piece of conductive thread to sew down your snaps. Stitch down one snap, sew along your dotted line, and then sew down your other snap. You will need a very long piece of thread for this. Here is another great Adafruit tutorial on hand sewing with conductive thread.
Step 5: Adding the Bluefruit and Battery
Preparing your Bluefruit:
Before you add your Bluefruit, you will have to solder on the 6-pin right angle female header and the JST connector. Once you've added these pieces, connect the male header and lay down the Bluefruit onto your felt. Place a dot under the 4 large corner holes of the Bluefruit and make dotted lines between the associated snap points and your male pins using the Sharpie. (Refer to your prototype.) NOTE: I dotted the four outside corners of the Bluefruit, but I don't think this is necessary.
Solder the crimp tubes onto the male pins making sure to stagger them. This will help you space out your knots and prevent shorts when you sew your conductive thread.
Sew the conductive thread:
Follow the instructions for sewing your conductive thread in Step 3. This time you will use one end of your conductive thread to sew down the snaps and the other to sew down the crimp tubes. Once you've stitched down the crimp tubes, I recommend stitch the conductive thread away from the crimp tube spreading out the knots to avoid shorting.
Adding the Elastic:
Lay the battery next to the Bluefruit and mark lines to the right and left of the battery. You will use these lines as stitch guides for the elastic. Before you sew down the elastic, hand sew two male snaps to one end of the elastic. Lay this end down to the left of the Bluefruit and mark dots where you will sew the female side of the snaps. Sew down the two female snaps to the felt and snap down your elastic. Flatten down the elastic and sew down the elastic along your marked lines to hold the battery. (You can do this by hand or with a sewing machine.) Trim any excess elastic.
Step 6: Adding Clasps and Straps
Trim excess felt:
Now that you have all of the electronics on your felt rectangle, it's time to finish the armband. Trim any excess felt from the top and bottom of the band making the band as thin as possible. Wrap the felt around your arm to get a sense of how wide you want the armband to be. If you plan to use this with students, make sure you keep the felt long enough to accomodate male and female students. Once you have a maximum length, add 3 - 4 inches of length to one side of the armband to make the clasps. Cut off any excess length.
Lay out your felt, trace and cut three "fingers" onto the excess length you assigned for clasps. (I made mine curved for aesthetic purposes only.) Take out another square of felt, trace the fingers and cut out the shapes. Pin and sew down these extra fingers onto your armband. Leave a small hole. Insert one of your magnets into the hole. Sew a line across the finger to hold the magnet in place at the tip. Insert a second magnet and sew a line across the finger at the base. Sew the insertion hole closed.
Cut strips of felt to make the straps. NOTE: In the future, I would use thin ribbon or trim that will more effectively hold shape when clasped. I would also make more straps to accomodote more arm sizes. Sew down the straps as shown in the image.
Step 7: Programming Your Flora
Pair the Bluefruit:
Now that the armband is complete, it's time to set it up to talk to your computer. Follow the pairing instructions found in this Adafruit tutorial.
Program Your Flora:
If you haven't worked with the Flora or other Adafruit products before, I strongly recommend looking at this Flora Adafruit tutorial. You will also need to download Adafruit's version of the Arduino IDE, which is available here.
I made a couple of Arduino patches for this armband:
"GyroWireless.ino" is for the Adafruit 9-DOF, LSF9DFO.
"VariableResistorWireless.ino" is for any variable resistor sensor (pressure, bend, potentiometer, etc.)
Use the Armband:
Now that you have your armband setup, you are ready to go! You can connect any computer program that can receive serial data to (if you so choose) create realtime audio/visual feedback. For my class, I used Max/MSP to analyze the data and generate feedback. I attached some of the starter Max/MSP patches I built for my to explore.