Fitness Tracker Teardown is a Lesson In Design for Manufacture

If the trends are anything to go on, after the success of Fitbit we are nearing a sort of fitness tracker singularity. Soon there will be more fitness trackers on wrists and ankles then there will be stars in the sky. We will have entire generations who will grow up not knowing what life is like without the ever-present hug of a heart monitor strapped across their chest. Until then though, we can learn a bit of design for manufacture from this excellent teardown of a watch shaped fitness tracker.

This tracker has a nice round e-paper screen, which could be a welcome part in a project if they start washing up on the shores of eBay. The rest of the watch is a basic Bluetooth low energy module and the accessory electronics wrapped in a squishy plastic casing.

There’s a lot of nice engineering inside the watch. As far as the electronics go, it’s very low power. On top of that is plenty of clever cost optimization; from a swath of test points to reduce quality issues in the hands of consumers to the clever stamped and formed battery tabs which touch the CR2032 that powers it.

The teardown covers more details: the switch, what may be hiding behind the epoxy globs, the plastics, and more. One thing that may be of interest to those that have been following Jenny’s excellent series is the BOM cost of the device. All in all a very educational read.

Dual Axis Solar Tracker with Online Energy Monitor

[Bruce Helsen] built this dual axis solar tracker as one of his final projects for school.

As can be experimentally verified in a very short timeframe, the sun moves across the sky. This is a particularly troublesome behavior for solar panels, which work best when the sun shines directly on them. Engineers soon realized that abstracting the sun away only works in physics class, and moved to the second best idea of tracking sun by moving the panel. Surprisingly, for larger installations the cost of adding tracking (and its maintenance) isn’t worth the gains, but for smaller, and especially urban, installations like [Bruce]’s it can still help.

[Bruce]’s build can be entirely sourced from eBay. The light direction is sensed via a very clever homemade directional light sensor. A 3D printer extruded cross profile sits inside an industrial lamp housing. The assembly divides the sky into four quadrants with a light-dependent resistor for each. By measuring the differences, the panel can point in the optimal direction.

The panel’s two axis are controlled with two cheap linear actuators. The brains are an Arduino glued to a large amount of solar support electronics and the online energy monitor component is covered by an ESP8266.

The construction works quite well. If you’d like to build one yourself the entire BOM, drawings, and code are provided on the instructables page.


It’s 10 PM, Do You Know Where Your Space Station Is At?

I still remember the first time I saw a satellite, I was 12 years old and was camping far away from the city lights. As I gazed up at the night sky, I could actually track satellites with my naked eye as they zoomed across the night’s sky. It was amazing. Nowadays, it’s getting harder to spot relatively small satellites with light pollution from large cities.

The International Space Station (ISS) on the other hand is a large piece of hardware — it’s about the size of a football field, and according to NASA it’s the second brightest object in the night sky.  So why don’t we see it more often? Well, part of the reason is that you don’t know where to look. [Grady Hillhouse] set out to change that by building a what is basically a 2 degrees of freedom robot arm that will point you to where the ISS is at any given moment.

[Grady] uses a stepper motor for the azimuth, and a standard servo for the elevation, all powered by an Nucleo F401 development board, and an Adafruit motor shield and slip ring. The structure is made using some Erector set like parts from Actobotics.

He wrote the code from this open source project here. He’s currently cleaning up his code, and says he’ll be posting it up shortly. In the mean time, you can watch a video detailing the build in the video after the break. Or if you can’t wait, you can visit NASA’s web site to receive email or SMS messages on when the ISS is view-able in your hood.

Continue reading “It’s 10 PM, Do You Know Where Your Space Station Is At?”

Acoustic Impulse Marker Tracks Sounds With a Pencil

Acoustic Impulse Marker (aiming device)

Two students at Cornell University have put together a rather curious sound tracking device called an Acoustic Impulse Marker.

[Adam Wrobel] and [Michael Grisanti] study electrical and computer science, and for their final microcontroller class they decided to build this device using the venerable ATmega 1284p.

The system uses a three-microphone array to accurately position sharp noises within 5 degrees of accuracy. The microcontroller detects the “acoustic delay” between the microphones which allows it to identify the location of the sound’s source vector. It does this using an 8-stage analog system which converts the sounds from each microphone into a binary signal, which identifies when each microphone heard the noise. The resultant 3 binary signals are then compared for their time delay, it selects the two closest microphones, and then does a simple angle calculation based on the magnitudes of each to determine the sounds position. Continue reading “Acoustic Impulse Marker Tracks Sounds With a Pencil”

Extrinsic Motivation: Smart Antenna Tracker for R/C Aircraft

Long distance FPV (First Person View) flying can be a handful. Keeping a video feed alive generally requires a high gain directional antenna. Going directional creates the chore of keeping the antenna pointed at the aircraft. [Brandon’s] smart antenna tracker is designed to do all that automatically. What witchcraft is this, you ask? The answer is actually quite simple: Telemetry! Many flight control systems have an optional telemetry transmitter. [Brandon] is using the 3DRobotics APM or PixHawk systems, which use 3DR’s 915 MHz radios.

The airborne radio sends telemetry data, including aircraft latitude and longitude down to a ground station. Equipped with a receiver for this data and a GPS of its own, the smart antenna tracker knows the exact position, heading and velocity of the aircraft. Using a pan and tilt mount, the smart antenna tracker can then point the antenna directly at the airborne system. Since the FPV antenna is co-located on the pan tilt mount, it will also point at the aircraft and maintain a good video link.

One of the gotchas with a system like this is dealing with an aircraft that is flying directly overhead. The plane or rotorcraft can fly by faster than the antenna system can move. There are a few commercial systems out there that handle this by switching to a lower gain omnidirectional whip antenna when the aircraft is close in. This would be a great addition to [Brandon’s] design.

Hacking SPOT personal satellite tracker to pass more information

For less than $100 you can buy a little tracking module that will upload your location to a satellite. But you’ll only get latitude and longitude information. [Natrium42] spent some time reverse engineering the hardware, and the communications protocol, to allow custom data to be transferred using a SPOT module.

The flat fee for the hardware includes a one-year service plan allowing you to tack your device on the SPOT website. [Natrium42] started poking around in the transmitted data packages, and figured he could push custom messages like altitude data if he had some way to encode it as a valid latitude/longitude package. He found that location data is transmitted as two sets of three bytes each. The four least significant bits of each set get rounded by the server, leaving a total of 40 usable bits between the two data sets. He wrote encoding and decoding functions that will allow you to transfer whatever information you want.

So what is this good for? To get the process working he removed the MSP430 microcontroller from the board and is using his own replacement. So you can transmit GPS data from the onboard module, your own module, or sensor data for anything you’re able to hook up the to the replacement uC.

Laser tracker replays competitive rock wall climbs


Instructables user [PenfoldPlant] is a big fan of indoor rock climbing, and while watching others make difficult climbs, he has often wondered if he could follow the same route up the wall. Unfortunately, aside from watching the other climbers and hoping to remember the path they have taken, he found there isn’t much you can do to ensure that you have precisely replicated the climb.

He thought awhile and came up with a laser tracking system that can be used to record a climber’s ascent, then replay it any number of times. This allows climbers to be able to replicate other climbers’ paths as well as compete against one another in timed races.

This works much like the “ghost” feature found in most racing games, though the process is half manual/half automated. The initial ascent is recorded by manually tracing the climber’s route with a laser pointer as they climb. The path is recorded and then can be replayed, courtesy of the onboard Arduino.

It really is a neat system, and while it works pretty well already, we think there is still room for enhancement. It wouldn’t be extremely difficult to have the climber wear some sort of light beacon that could be tracked using a web cam or other recording device, taking the manual labor out of the equation. In that case however, we imagine the Arduino would need to be swapped out for something a touch more powerful.

Stick around for a quick video of the tracking system in action.

Continue reading “Laser tracker replays competitive rock wall climbs”