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20. Project presentations

Document a final project masterpiece that integrates the range of units covered, answering:

What does it do?

In general, my project is a 3D printed hand that follows the movements of the human hand with wireless control.

First, the operator will use in his hand a mechanism that holds the flexible sensors, these are in charge of detecting the flexion of human fingers, this information is captured by the digital analog converters of the microcontroller, then they are processed and finally sent to a second microcontroller. through a wireless bluetooth network.

On the other hand, the second microcontroller that is connected to the mechanical hand receives the data received by the slave bluetooth and sends this information to the servomotors that allow to replicate the movements of the human fingers, this is possible thanks to the fact that the servomotors transmit the movement along all the phalanges of the finger through the tension of the fishing line and to the flexible joints that join the phalanges.

Who’s done what beforehand?

At Fab Academy I saw two projects where a hand is used, the first project is a rehabilitation hand by Roberto Moya and the other is a bionic hand for a physically disabled person by Prashant Gade.

In my case, my project is purely educational, I do it so that the students have modules in which they observe the ways of applying the learned concepts and how they can be combined in a project.

What did you design?

From the remote control mechanism:

  • I designed the rings for each phalanx that support the sensors.
  • I designed the sensor connection PCB.
  • I designed the support for the PCBs used.
  • I Developed the data acquisition and transmission program.

From the mechanical hand:

  • I designed the palm of the hand, phalanges of the fingers and joints.
  • I designed the PCB for the servomotors.
  • I designed the support for the hand, servomotors and PCB of servomotors and microcontroller.
  • I developed a program for receiving data and controlling servomotors.

What materials and components were used?

Quantity Material Description
02 3D filament PLA
01 Acrylic 90cmx60cm
01 fishing line spool

Quantity Component Description
02 microcontroller ATmega328p
05 servomotors 90cmx60cm
02 HC-05 Comunication Bluetooth
05 Flex sensor Resistive sensor
02 Power supply Supply 5Vdc

Where did they come from?

I had all components and materials.

How much did they cost?

Quantity Material Description Cost
02 3D filament PLA $ 50.00
01 Acrilic 90cmx60cm $ 25.00
01 fishing line spool $ 7.00

Quantity Component Description Cost
02 Microcontroller ATmega328p $ 10.00
05 servomotors 90cmx60cm $ 125.00
02 HC-05 Comunication Bluetooth $ 10.00
05 Flex sensor Resistive sensor $ 90.00
02 Power supply Supply 5Vdc $ 25.00

What parts and systems were made?

Manufacture in 3D printer:

  • Palm of the hand, phalanges and joints.

Manufacture in laser cutter:

  • Support for mechanical hand and servomotors.
  • Rings for the remote control mechanism.
  • Support for remote control PCB.

Tabletop CNC manufacturing:

  • PCB for microcontroller of the mechanical hand.
  • PCB to connect the servomotors.
  • PCB to connect the sensors.

What processes were used?

Additive manufacturing processes such as 3D printing and subtractive manufacturing processes such as laser cutting and CNC engraving were used.

What questions were answered?

  • It was the first time I worked with the flexible sensors, I thought that they changed their value with any type of flexion, but they only respond in one direction of flexion.

  • It was also noticed that the fingers have slight oscillations, it is something that was not foreseen, perhaps said oscillation can be eliminated by taking the average value over a period of time.

  • At the beginning of the project we did not know about the force that the mechanical hand could exert, with the grip tests carried out the weight that the mechanism can hold was determined.

What worked? What didn’t?

The data acquisition and processing work well as well as the control of the motors when the data arrives at its destination, everything manufactured works as planned.

There are problems with the Master-Slave bluetooth network, after a few minutes it goes down, we will try sending data more slowly, that is, we will send 4 data frames per second.

How was it evaluated?

I performed grip tests with objects of various shapes such as:

  • A ball
  • A small jar
  • A roll of packing tape.

What are the implications?

With this project I will be able to teach my students the use and integration of sensors, such as flexible sensors and actuators such as servomotors in the same project, I will also be able to teach the configuration of bluetooth devices to establish a Master-Slave network as well as the organization of the data transmission frames and the problems that may occur during the transmission.