Insert and Integration

Insert

3D printed out of ABS to contain all electrical and plumbing components.

There are pockets for the bladders to sit in and have holes that allow the ports to stick out.

Tubes follow grooves from the bottom to each of the bladders that allow for air flow.

Force sensors lie in between the bladders and the inserts that are used to measure the relative pressure that is being exerted on that bladder.

There are brass metal inserts that are inserted into 3 locations that remove the need to tap the plastic and allow screws to be easily threaded into them.

Electrical

The final board consisted of 4 Transistors (PN: TIP120), 4 diodes, 4 1k resistors, 4 10k resistors, a driver board (PN: TB6612FNG), and the Adafruit nRF52840

The transistors, diodes and 1k resistors were used to switch the state of air valves (PN: FA0520E) . This would allow the two air pumps to be connected to the same line and switch from pumping to vacuuming.

The speed of the air pumps was controlled by the motor driver which sends a PWM signal at varying percentages.

Force sensors in the insert would be wired onto the board with 10k pull down resistors and connected to four analog to digital converters.

Software

Using the Mu Editor and Circuit Python, code was uploaded onto the Adafruit nRF52840.

The first step is to connect to the mobile device using Bluetooth. On the mobile device the application “Bluefruit Connect” is required. Displaying a Red LED on the microcontroller when not connected and green when successfully connected.

Then the code waits for the user to give an input. The user is given many options on the control pad, but only 3 buttons will have a response. Button 1 will Vacuum all the bladders, allowing the user to easily place their limb into the prosthetic. Button 2 will launch the main sequence. Which is reading the data from the force sensors and comparing it to the target. It will pump the air bladders first and then make sure the overshoot does not exceed the range. If it does it will vacuum until below that value. This is to ensure that the bladders don't over inflate and cause pain to the user. It will then cycle through the remaining bladders repeating the same process. Button 3 allows the user to stop the main sequence from button 2.

Integration

This part of the project is how to put everything together.

The insert is suspended by three screws that attach to the treaded inserts.

Bellow the insert is space for plumbing, electrical and the solenoids to be stored.

On the back of the prosthetic is space to store the two motors, battery and circuit board

Made By: Anton Gerasimov

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