The key points we will look at when making the wrist bands is to have the least amount of connection possible as the more connections there are the more chance that will will have noise in our signal. Second is the comfort of the wrist bands, you don't want to be hurting the person that you are measuring. Finally practicality, the wrist bands need to be easy to take on and off, I learnt this by doing prototypes first.
Remember this is just a guide for what I did in 3 weeks and by no means is this the best way to do it or even the best parts that you can use but I decided to put this up because when I started I couldn't find anything like this online.
NOTE: THE BOARD THAT WE ARE PLUGGING OURSELVES INTO ISOLATES US FROM THE MAINS POWER SUPPLY, YOU SHOULD ALWAYS BE CAREFUL WHENEVER YOU ARE USING ELECTRONIC EQUIPMENT.
Step 1: Materials
So first was the material for the wrist band. I went to Spotlight, this is a fabric/arts and crafts store for those who don't know it. I got 2 meters of black woven band as you'll see in picture later and 2 meters of velcro that matched the width of the band. I also got 4 D buckles, thread and sewing needles.
Then off to Jaycar (local electronics store) I got 3 meters of coaxial cable with a solid copper core, heat shrink, resin solder, and gold coated quick terminals.
Step 2: Preparing the Cables
On the end that we are going to put into the quick terminal I then put heat shrink over the end to make sure that none of the outer wire will touch the copper wire or terminal (this is important because in the board that we feed the signal into the outer wire will connect to ground).
On the cable that goes to the leg I also put heat shrink on the other end just because it only goes to ground.
Next is the soldering. Feed the copper wire through the bottom of the quick terminal and crimp the terminal onto the cable as much as possible. Take your iron and resin solder and heat both the wire and the terminal and allow the solder to flow onto it which should create a nice connection like the one in the image.
Step 3: Preparing the Bands
Not too sure what the stitches are called but I did 3 rows to secure it. First a looping stitch over the end, then a cross stitch in the middle and finally a running stitch near the D buckle.
In the image below you can't really see the first line of stitch that I did.
Step 4: Connecting the Components
In the picture you can see the way I did it, I cut a small slit in the band with a stanley knife and pushed the terminal through. To connect the quick terminal to the band I first tried some 4 minute quick hardening clear epoxy. It didn't work took forever to dry and I eventually wiped most of it off and when it had dried I sand papered the rest off. I ended up using 3 minute superglue and this worked really well.
The little bit of band below the terminal I also superglued to the cable.
Step 5: Adding the Velcro
The main part of this is just making sure you have enough velcro on each side so that when it goes around your wrist it'll line up, that's not that hard just try it on yourself and measure it out before sewing anything on.
After this your done, congratulations you're now the proud owner of ECG electrodes.