Know what you’re getting into.
Making a Netflix personal trainer requires a little technical know-how, including comfort with building basic electronics and doing some coding. You may also want access to a CNC router or 3D printer to create your case. To speed things up, we designed a custom PCB to hold all your components, though you’re welcome to create your own board.
There are plenty of opportunities to trick out your personal trainer by tweaking the code and customizing the exterior.
Before you get started, download this .zip file with everything you’ll need to make your personal trainer, plus a handy FAQ.
Understand the mechanism.
The personal trainer connects to your phone or tablet via Bluetooth and uses an accelerometer to monitor your activity level during your workout. You set a threshold for your activity level based on how hard you like to work out. Every time you fall below that threshold, your personal trainer will momentarily pause or mute your music, and your selected Netflix character will deliver motivational words to keep you going.
If you also happen to be watching Netflix on iOS while working out, your Personal Trainer will auto-pause your show every time you stop and deliver more motivational goodness. If you want to keep watching, you gotta keep moving.
Gather your materials.
Below is a general list of what we used to make our personal trainer. Our detailed bill of materials lists items in the order we recommend soldering them to your PCB.
Feel free to make substitutions or experiment with different materials based on how you like to work out—or what will get you jazzed about working out. Remember to order extra components just in case!
We designed a PCB that acts a shield of sorts. It holds the microcontroller, Bluetooth module, audio module, accelerometer, charging circuit, and a few other various components. Of course, you can build the trainer using your microcontroller of choice (such as a Photon), but if you’re using our PCB design, it’s made to fit a Trinket Pro 3V. There are two headers attached to the PCB, which you’ll use later. Everything you need to create your PCB is in the .zip file.
Of course, you don’t have to use the custom PCB, but it helps keep things small and tidy. If you don’t use our PCB, you may want to change out some of the smaller components out.
Assemble the electronics.
Now it’s time to get out the soldering iron. All the components are labeled on the back of your PCB. Check out the schematic, then solder everything in place. Some of the components are super tiny (especially the accelerometer), so we broke out the heat gun and soldering paste.
Customize your code.
To help you get your personal trainer up and running, we’ve provided this Arduino sketch. Most of the code is set and ready to go—you just need to decide how you like to work out and which Netflix character you want to motivate you.
You can choose from four activity levels, which will determine how high your threshold is set. Choose “Walk” if you like to take it easy; choose “Run” if you’re going to be in beast mode. This will ensure you only receive motivation when you actually need it. You can also tweak the code based on whether you like to listen to music or watch Netflix while working out.
Create your casing and faceplate.
We fabricated a fancy case out of wood on a CNC router using this 3D .step file, though you could also use a 3D printer. Feel free to design your own custom enclosure—and we’d love to see what you come up with.
Of course, one of the best parts of using your personal trainer is showing off the character you’ve chosen as your coach. We created a faceplate by printing a character pic on clear acetate and adhering it to an acrylic panel. Once it’s ready, you can use those headers that were included in your custom PCB to mount it.
One thing to note: If you don’t hardcode a Netflix character as your coach, your personal trainer will automatically detect which faceplate is attached (using the resistors on the back), and select that character as your coach.
You’re ready to crush it.
It’s time for the moment of truth. Clip your personal trainer to your waistband or armband, then turn it on. The LEDs will cascade until it pairs with your phone, at which point one LED will remain lit.
As you work out, the LEDs will act as an activity meter. Three lit LEDs means you’re above threshold (nice work!) while one lit LED means you’re below threshold…and about to get some words of motivation. As your coach gives you a pep talk, the LEDs will act as a VU meter.
Once you really get going, you may find you’ll need to tweak the threshold to match your activity level—or you can add a dial so you can tweak it on the fly.