Introduction to Embedded System
(Supervisor: Dr.Muhammad Asim Samejo)


DIY FAB VENTILATOR
(Emergency Use Ventilator)


Introduction

The main objective of this project is to design a low-cost ventilator device with mechanical system that is able to provide consistent and accurate ventilation with positive pressure (for adults, toddlers & infants).
This device will be having the facility of user-interface system in which one of three modes will be selected for ventilation at a time.

Design Requirements:

For proceeding with this objective, we will be provided the essential components and other parts will be printed in Computer Numerical Control(CNC) machine and Ultimaker 3D printing machine in Fabrication Lab and Workshop Lab.

Following components are considered for design requirements:



High Level Design


Sample Images of Final Design:

The following picture of product has been focused upon as a reference design:


From this design, an idea will be taken and a similar product will be designed.



The following picture of inside's circuit diagram has been focused upon as a reference which is to be updated:


This reference circuit is based on two Arduinos which are connected by I2C protocols in which two of them are connected with each other with I square C(I2C) protocol by connecting two analog pins A4 & A5 of both Arduinos. One Arduino is Master which is sending signal to other Arduino which is Slave. Master Arduino is for LCD Display and Rotary Encoder and Slave Arduino is for motors.


From this circuit diagram, we have been instructed to convert the whole scenario from two Arduinos to one Arduino which has proved to be a grave challenge.

In other words, we have been guided to created our own dedicated PCB Circuit which should run all the components with only one micro-controller.

Mechanical Drawing:

The following picture is the roughly drawn mechanical design of the product:
Different dimensions (in inches) have been assigned to the parts keeping in mind the size of Ambu Bag and other parts.



The following picture is the roughly taken down circuitry inside the product:

Project Execution Plan:

All the electrical and mechanical components will be tested and learnt to control one by one, and then collectively be controlled to get the genuine idea and understanding. In this manner, the provided referenced circuit will be implemented.



Distribution of Tasks:

S.No Tasks Pictures Distributed to
1 To operate the simple Servo Motors before reaching the Dynamixel Motors through PWM Pin of Arduino UNO to get the idea of controlling them. Both
2 To operate the LCD Display with I2C Module to get the idea of controlling it. Both
3 To operate the Rotary Encoder with LCD Display with I2C module to get the idea of controlling it. Hasnain Ali (033-19-0028)
4 To implement the given circuit with two Arduinos as reference. Both
5 To implement the basic code of Dynamixel Motors to get the idea of operating them. Both
6 To start connecting Rotary Encoder and LCD Display with I2C Module with Dynamixel Motors from scratch.  
Hasnain Ali (033-19-0028)
7 To program and finalize the complete code step by step. Mohammad Adeel (033-19-0020)
8 To design in CAD. Hasnain Ali (033-19-0028)
9 To work on PCB Designing. Team of FAB Lab
10 To solder components on PCB. Mohammad Adeel (033-19-0020)
11 Printing the PCB. Team of FAB Lab
12 Printing all 3D parts.
Team of FAB Lab
13 To assemble everything together. Both
14 To make report.
Both




Execution of General Tasks and Main Tasks by Using Arduino UNO:




Design

High Level System Diagram:

The following circuit diagram has been created in Fritzing application software.
This became our finalized circuit design after receiving suitable components and working hard on coding for having one micro-controller.

Description of Principle of Operation:

In this circuit, 12V DC power supply has been connected to the one Dynamixel Motor and other Dynamixel Motor is connected to the first Dynamixel Motor serially which is fixed and decided way of connecting as many Dyanmixel Motors. Only one pin of one Dynamixel Motor is sufficient to be connected to the D1(Tx) of the Arduino which is one of the two pins of Arduino for serial communication. With LCD Display, I2C Module has been connected to convert the serial data travelling process into parallel data travelling process which reduces the pin connections. Here, with module, only two analog pins A4 & A5 of Arduino have been connected to the SDA(Serial Data) & SCL(Serial Clock) of the I2C Module. Rotary Encoder 's three pins have been connected to the digital pins D2, D4 and D3 of the Arduino. LCD Display with I2C Module and Rotary Encoder both need only 5V DC Power Supply which can be provided via Arduino's 5V & GND pins.

When the Arduino code is uploaded in the Arduino UNO, there will be a menu with options (Adult Mode, Toddler Mode & Infant Mode) being displayed in the LCD Display, and one of the options can be chosen with the help of Rotary Encoder. In this manner, Dynamixel Motors will start and push the Ambu Bag from left side and right side as per the requirement.



Choice of Major Components and their Brief Descriptions
Component Name Picture Description
Dynamixel Motor
According to the Servo Motor in the reference circuit, at least 17.2 kg.cm torque is needed to push the Ambu Bag effectively.
For approaching this scenario, we have Dynamixel Motors which can be operated at 12V DC Power Supply which is easier to be connected with just one pin to produce the similar torque to push the Ambu Bag.
I2C Module
This module has been used with LCD Display to convert serial data travelling process into parallel data travelling process and for reducing pin connections from sixteen to four.
Rotary Encoder
This device is more prefarable than an ordinary potentiometer because of its more sensitive internal construction and continuous rotation and having a button in its knob.
In this manner, it is convenient for navigating the menu.
Buck Converter
(will be used in the PCB ahead)
As 12V will be used by Dynamixel Motors and 5V will be used by LCD Display with I2C Module and Rotary Encoder, this device, used as a Voltage Regulator, will step down the 12V DC voltage to 5V DC Voltage only for Display with I2C Module and Rotary Encoder. Its potentiometer is adjusted to produce 5V from 12V DC Power Supply only for LCD Display with I2C Module and Rotary Encoder.


Connectivity of Components by Protocols:

Three main protocols have been used in the circuitry of this project.

  1. UART Protocol
  2. SPI Protocol
  3. I2C Protocol


  1. UART Protocol:

    UART stands for Universal Asynchronous Reception Transmission. This protocol permits the arduino to communicate with serial devices through the pins D0(Rx) & D1(Tx).
    Dynamixel Motors have been connected by using this protocol from D1(Tx) digital pin.



  2. SPI Protocol:

    SPI stands for Serial Protocol Interface. This protocol is implemented for two way communication between two devices especially when there is the involment of clock signals.
    Rotary Encoder has been connected by using this protocol from D2,D4 & D3 digital pins.



  3. I2C Protocol:

    I2C stands for Interintegrated Circuit or I square C. It is especially used when master and slave devices are connected for sending and receiving the signals as well as for displaying text in LCD conveniently.
    LCD Display with I2C Module has been connected by using this protocol from A4 & A5 analog pins.




Electrical Schematic



Description

From the beginning of our this project, our circuitry is based on Arduino. Hence, the schematic has been created similar to that of Arduino in which ATMEGA328p micro-controller of SMD package has been used along with LEDs, capacitors, resistors, buck converter (voltage regulator), and a crystal oscillator. In addition to these, male connectors have been attached for our components and for uploading the code with FTDI Cable and for Bootload. Among these connectors, only one three pin connector has been attached for one Dynamixel Motor ,because the other Dynamixel Motor will be connected serially with the first one.


PCB Layout



Challenges

Firstly, we both tried to make the PCB on Eagle software, but we could not do that because of the complexity of wires.
Then, the team of FAB Lab helped us create the design of two layers and solder the IC of ATMEGA328p micro-controller of SMD package.
Secondly, there was the error of reversed polarities of +ve & -ve terminals. It was resolved by connecting the 12V power in other direction.
Thirdly, there was the error from the PCB of having 5V for the Dynamixel Motors (needing 12V) which must have been for only Rotary Encoder and LCD Display with I2C Module. It was resolved by the team of FAB Lab by some extra connections behind the board.

Bill of Material



SRM Machine Working



Clean Printed Circuit Board

               
First Layer                                                                                         Second Layer



With Buck Converter

Populated Printed Circuit Board




               

               
                                                                                                With Bill of Material

Burning the Bootloader

               

               

                  

Procedure of Burning Bootloader

To burn the Bootloader in the new Micro-controller, a Bootloader Circuit is required whose few pins are connected with few pins of the nine-pin header of the PCB. The FTDI cable is connected with its header. From the Arduino IDE software, Burn Bootloader option is chosen from Tools and Bootloader is burnt. In this process, two USB data cables are required which are connected to the PC, one for Bootloading Circuit and other for FTDI Cable.


Challenges in Booting Up

Successfully after burning the Bootloader, firstly, we had been instructed to disconnect the Buck Converter whenever we had to upload the code in the Micro-controller only with FTDI Cable, because it could cause the voltage to become double which might destroy the whole PCB with over voltage supply. Secondly, there must not have been any connection with the PC while connecting the Buck Converter for running the circuit with components.


Successfully Operating Circuit



Video


Demonstration of Operational the Circuit

In this PCB, basically, four components are to be attached which are Dynamixel Motor, LCD Display with I2C Module, Rotary Encoder, and a Buck Converter. While operating the circuit, 12V voltage is supplied to the PCB from which all the 12V voltages are consumed by Dynamixel Motors. But, LCD Display with I2C Module and Rotary Encoder consume only 5V which are provided by the Buck Converter which steps down the 12V DC voltages to 5V DC voltages.
In this manner, only one 12V DC Power Supply is used effectively for the operation of whole circuitry.


Flow Code of the Software Design



Main Construct of Program



Challenges

Firstly, we had to study the whole scenario and write our own code of one Micro-controller. For this, we analyzed all the libraries and their built-in functions to be used. Secondly, we had to create the conditions for Rotary Encoder under which LCD Display with I2C Module could be controlled. Thirdly, we had to understand the serial connection of Dynamixel Motors along with their fixed ID numbers which were mandatory in the built-in functions of the library of Dynamixel Motors. Lastly, with many user-defined functions, we merged everything and programmed a suitable code for this.


CAD Design of Enclosure




Parts to be Cut
Back Designed by us
Front Designed by us
Bottom Designed by us
First Top Designed by us
Second Top Designed by us
Third Top Designed by us
Fourth Top Designed by us
Left Designed by us
Right Designed by us
Rod Two pieces of about 6 inches are to get cut and purchased from market



Parts to be 3D Printed
Bumper Taken from website
Support Taken from website
Clamp Arm Taken from website
Gear Taken from website and modified
Housing Base Taken from website
Rail Taken from website and modified
Ball Bearing Taken from SolidWorks
Sliding Part Designed by us
Assembly of Housing Base, Rail, Ball Bearing & Sliding Part Assembled by us in SolidWorks
Motor Mount Designed by us


Assembly of all Parts









Design Consideration

The idea of the design has been taken from the reference website, and the dimensions have been set in inches. According to the height and diameter of Ambu Bag, the dimensions have been decided, and upper part has been built according to the movement of bumper. Inside the enclosure, there will be the dedicated PCB and wires to connect the components internally. All the components are outside the enclosure execpt PCB to whom 12V DC power supply will be connected from the big hole as to be seen.



Fabrication, Design and 3D Printing


3D Printing in the Ultimaker




Procedure

The STL file is opened in Cura slicing 3D printing application where the part is viewed and set according to the slicing pattern, and time taken can also be taken in. Then, GCode is formed which is copied in the SD Card and inserted in the Ultimaker which understands the GCode, and prints the part by slicing the hot plastic material in the required pattern.








               



Cutting Parts in the CNC Machine




Procedure

In this process, DXF file is used and adjusted in the software of CNC Machine in which the inside cuts and outside cuts are decided. For holes, inside cut process is chosen for which separate commands are set up.



               





Getting Two Rods Cut from the Market






Assembly of all Parts


               

               

               


Results


Final Design

               


Cost of the Project

Component Cost
Full PCB Rs.4552
LCD Display Rs.488
I2C Module Rs.163
KY-040 Rotary Encoder Rs.163
Dynamixel Motors Rs.23413
Plywood Rs.4227
Plasting of 3D Printing Rs.4065
Metal Rods Rs.260
Ball Bearings Rs.1500
Total: Rs.38,831



Business Model of the Project

Nowadays, every product, especially highly proficient and technological, is demanded a lot in the market. Here, our mission is to create somehow an affordable and portable ventilator which can be used in case of extreme emergencies just like in ambulances. As the world has been caught by the highly contagious of COVID, such project is helpful in this critical condition in which the patients can be provided the convenient means of breathing. The two main advantages of this project are that it is a little bit affordable and portable to carry everywhere in case of serious and critical conditions.




Reference

Click here to visit the website of reference.

Source Code

Click here to download the source code.

Eagle Files

Click here to download the Eagle Files.

CAD Files

Click here to download the CAD Files.

Fritzing

Click here to download the Fritzing File.



Conclusion

In this course, we felt fortunate to learn plenty of new things by the strategy of self-learning. It must be said that this course proved to be different from the rest of courses. We were free to apply new things and to do brain-drilling activities.
While making project, we learnt about group management, coordination and cooperation with one another. Our concepts were revised and polished, and teaching and learning activities were always together.
Although it was the big loss of having the off days during the session, yet we tried our best to overcome the situation and hardships. In our project, at the end, some mechanical errors occurred, which are the lessons for us to be more careful for them ahead.
To sum up, this course is full of learning. All are encouraged to study this with the great pomp and show.






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