Design thinking

The idea is: As we know, we need to squeeze an ambu bag, and I planned to do that with a simple mechanism

• So I chose a reciprocating-rack-and-pinion mechanism, you can take a look here

• in this mechanism we convert the rotation motion into linear motion, and the arm will push the ambu bag

• I used Nema17 stepper motor for this try

first prototype

Failures&constraints

• I couldn't combine the mechanism and the ambu bag in a good looking frame
• there is a problem in the slider fixation
• we have 2 levels of connections: from motor to gear,nthen from gear to slider arm,later on, this may result in mechanical problems

In this release, I relied on an open source mechanism Darren Lewis then I modified it

Advantages of this mechanism:

• the torque moves from motor to the arm directly
• Stable structure and good looking frame
• Portable

Disadvantages:

• We need relatively high torque, and Arm fixation method
• You can find the Bill of materials here

Motor Selection and power calculations

As I said for the first time we use the Nema17 without any calculations we did that actually for two reason

1. we want to test to concept fast with what we have in the lab
2. Nema17 was the motor that have the biggest torque in our lab ~=0.4N

So as much as we hoped it will work it didn't of course and Nema17 wasn't able to squeeze the Ambu-bag as you can see in the video ->

Electronics Design and production

• Before I start, I have read ATMEGA328 Datasheet carefully, you can find it here
• High Performance, Low Power AVR® 8-Bit Microcontroller Family
• Six PWM Channels
• 8-channel 10-bit ADC in TQFP
• 32-lead TQFP
• Operating Voltage:̶ 1.8 - 5.5V
• Speed Grade: 0 - 4MHz@1.8 - 5.5V, 0 - 10MHz@2.7 - 5.5.V, 0 - 20MHz @ 4.5 - 5.5V

// include the library code:
//#include 
#include 
LiquidCrystal_I2C lcd(0x27,20,4);  // set the LCD address to 0x27 for a 16 chars and 2 line display
#include 
//const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
//LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

Servo myservo;  // create servo object to control a servo
int pos = 0;  // analog pin used to connect the potentiometer
int val=0;    // variable to read the value from the analog pin
int potpin = 0;
int a=0;
int value=0;
int T=0;
int dn=0;
int val2=0;
int hold=0;

void setup() {
    lcd.init();                      // initialize the lcd 
  // Print a message to the LCD.
  lcd.backlight();
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object
  // set up the LCD's number of columns and rows:
  //lcd.begin(16, 2);
  Serial.begin(9600);
  // Print a message to the LCD.
  lcd.print("Breathing");
  T=millis();
}

void loop() {
  val=analogRead(A0);
  val = map(val, 0, 1023, 0, 25);
  value=val+9;
  Serial.println(value);
        lcd.setCursor(0, 1); 
       lcd.print(value); 
   val2=analogRead(A1);
   hold= map(val2, 0, 1023, 0, 500);
   lcd.setCursor(11, 0); 
   lcd.print("Hold");
   lcd.setCursor(12, 1); 
   lcd.print(hold);
  INH();
  delay(hold/2);
  EXH();
    delay(hold);
     lcd.setCursor(3, 1); 
    lcd.print(millis() / 1000);
    dn=((millis()-T)/1000);
   if(dn>=60){
    a=0;
    millis();
    T=millis();
    dn=0;
   }else{
        a++;
    lcd.setCursor(7, 1);
    lcd.print(a);}

  }
 void INH(){
  
    for (pos = 0; pos <= 90; pos += 1) { // goes from 0 degrees to 90 degrees
    // in steps of 1 degree
    myservo.write(pos);               // tell servo to go to position in variable 'pos'
    delay(val-4);                    // waits (val value)for the servo to reach the position
  }
}
void EXH(){
    for (pos = 90; pos >= 0; pos -= 1) { // goes from 90 degrees to 0 degrees
    myservo.write(pos);              // tell servo to go to position in variable 'pos'
    delay(val+5);                       // waits (val value)for the servo to reach the position
//   lcd.setCursor(0, 1);
//   lcd.print(pos);
}
}
      

Design and Implementation

• as i mentioned above, I relied on an open source mechanism Darren Lewis then I modified it
• 2D Design using Inkscape, you can learn more here

• export the file as dxf, then run it on your laser cutter machine

• using vinylcutter

• 3D Design for electronics case and POT cap -using Fusion360-, you can learn more here
• then I exported the design as .stl file
• then I used Cura to edit and print my parts

• Molding and casting here

• Push_Arm

• Servo_Motor

• Electronics box

• First Test
• Finally


presentation: [Video], [Slide]





License.

• After obtaining the approval, the project will be available under the MIT License




What is the next plan?

• 1- Work to bring a motor with more torque than the user.
• 2- Doing a test under the supervision of specialized doctors.

Finally, I would like to thank our Instructors May & Khaled for their patience and support in these exceptional times ☺

as well as my colleagues Mansour, Shakankery, Rowa, Fathiyah whom I had the honor to study with.

Really it's a never-ending fun journey 😃

• 2D design
• 3D design
• PCB_Design
• PCB_Fabrication
• ABB_CODE.rar