“The future depends on what you do today.”
Gandhi
Splint box
How it works
This device tracks the angle of Julian’s calf. If his leg does not go perpendicular to the ground, for a given period of time, the device vibrates to remind him to put his heel flat. If the initial series of vibrations do not get Julian’s attention…the subsequent beeping always does!
The device comprises an accelerometer, vibration motor, piezo speaker, LED, and switch, all controlled by an ATtiny85 microcontroller. The components are housed within a 3D-printed enclosure.
The main casing features an opening at its base through which a smaller sub-housing—containing the vibration motor—extends. This motor sub-housing is suspended by a spring from an internal arch within the main enclosure and protrudes from the rear of the main case.
This suspension mechanism allows the vibration motor to be inserted through the splint enabling direct contact with the leg. Decoupling the motor housing from the main circuit enclosure reduces structural rigidity and fragility, while simultaneously enhancing the tactile effectiveness of the vibration stimulus on the back of the calf.
The device is turned on while Julian is wearing his splints. It calibrates itself to the angle it is at when switched on, and uses this angle as its future reference angle to compare to.
To prevent the device from activating during walking, there is a 10 second 'grace period' before it vibrates. So, if the current angle is less than the initial ‘good’ angle for more than 10 seconds, it vibrators for a second. If the angle remains bad for another 5 seconds it vibrators longer. It gives four warning vibrations separated by slight pauses and finally, if the angle continues to remain bad, the device beeps.
Details
With the outer, top casing removed, you can see in the lower left portion of the image, the vibrator casing protruding of the flat frame. Above that is the arch attached to the spring supporting the vibrator.
Everything inside
Behind the yellow and black wire is the arch supporting the spring which holds the vibrator in its casing against the leg. Not only does the spring allow for a more powerful vibration, it also permits the vibrator casing to adjust its depth to always touch Julian's calf directly. So it doesn't matter what socks he wears for example.
To prevent the vibrator from getting damaged by the splint and to allow for a more powerful vibration to the leg, the vibrator component had to separate from the main casing. On the left is the vibrator similar to those in most mobile phones. Basically, the motor is spinning an asymetrical weight at the end of the shaft. This part is placed into the case on the right. The spring is at the top and is the only thing attached to a supporting arch in the main housing of the device.
Vibrator & case
Most of the components are visible here. To save space, the accelerometer is inverted and attached to the underside of the circuit, directly below the chip. The three sets of wires leading off are power, LED and switch. This was a big mistake, as it was almost impossible to manipulate the top of the case while attached to the bottom!
Everything inside
Arch with vibrator
Conclusion and considerations
All in all, quite satisfied for a first prototype. Many areas of improvement possible however! It is too big. There is no power management. With a few extra components it could even serve as a rudimentary gait analysis.