Build a Wearable Device Using an Arduino to Keep Astronauts Safe on Mars

This project follows the Engineering Design Process. Confirm with your teacher if this is acceptable for your project, and review the steps before you begin.

You will first assemble your circuit and test your code. This makes it easier to identify and fix any issues with your circuit or code. After everything is working, you will house your Arduino and circuit into a box and then test the wearble device. 

Assemble the circuit

See Figure 2 for the circuit diagram and Figure 3 for the final result of what your circuit will look like. Important: this is an advanced project. The instructions assume you know how to use a breadboard and how to build a circuit from a circuit diagram. Review the linked resources if you need help.

Figure 2. Circuit Diagram of the Safety Wearable Device

1. First, let's wire the 5V and GND pins from the Arduino Uno R4 to the breadboard. This will serve as your power distribution for all components.
   1. 5V from Arduino → Breadboard positive rail (+)
   2. GND from Arduino → Breadboard negative rail (-).
2. The GPS Neo 7M communicates via serial (TX/RX), so you'll connect the TX and RX to the RX and TX on the Arduino, respectively:
   1. VCC → Breadboard positive rail (+)
   2. GND → Breadboard negative rail (-)
   3. TX → RX (Pin 0) on Arduino
   4. RX → TX (Pin 1) on Arduino 
   5. Note: When using TX/RX for serial communication, you need to be careful not to interfere with the Arduino’s USB serial connection. For proper serial communication, you should disconnect these two wires when connecting to USB to upload code, then reconnect after the code is uploaded.
3. The MAX30102 Heart Rate and Oxygen Sensor wiring is as follows: 
   1. +ve → Breadboard positive rail (+)
   2. -ve → Breadboard negative rail (-)
   3. S → A1 on Arduino
4. The DS18B20 uses a 1-Wire communication protocol, and it needs a 10kΩ pull-up resistor between the Data Pin and VCC to work correctly.
   1. VCC → Breadboard positive rail (+)
   2. GND → Breadboard negative rail (-)
   3. Data Pin → A2 on Arduino
   4. 10kΩ Pull-up Resistor between Data Pin (A2) and VCC (5V)
5. The MQ-135 Gas Sensor uses analog output, so you'll connect the AOUT pin to an analog pin on the Arduino for reading gas concentrations:
   1. VCC → Breadboard positive rail (+)
   2. GND → Breadboard negative rail (-)
   3. AOUT → A0 on Arduino
6. The OLED Display communicates via I2C, so you'll connect SCL and SDA to the corresponding pins on the Arduino.
   1. VCC → Breadboard positive rail (+)
   2. GND → Breadboard negative rail (-)
   3. SCL → A5 (SCL pin) on Arduino
      1. Pin A5 has SCL functionality, even though this is not labeled on your Arduino
   4. SDA → A4 (SDA pin) on Arduino
      1. Pin A4 has SCL functionality, even though this is not labeled on your Arduino
7. The buzzer can be connected to any digital pin on the Arduino for feedback alerts:
   1. Buzzer Pin 1 → Pin D9 on the Arduino
   2. Buzzer Pin 2 → Breadboard negative rail (-)
8. 9V battery clip for portable power:
   1. Connect the battery clip from the Arduino kit to the battery
   2. Connect the other end to the battery jack of the Arduino

Image Credit: Hannah James / Science Buddies

Figure 3. Final result of what your circuit will look like once assembled and placed inside a box.

Test Your Code

Since this is a complex project with lots of moving parts, first we will test everything individually to confirm it all works, and then integrate everything together.

1. To start off simple download this code to first just display temperature on the OLED screen.
2. After that, try this code which allows you to blink the Arduino onboard LED using the heart rate sensor and your heartbeat.
3. This code contains the rest of the sensor capabilties. So now incoporate it into your script depending on which sensors you chose to use.
4. Now let's start incorporating the geofence capabilities! this code contains just that.
5. To obtain the GPS coordinates of your location, follow these steps:
   
   1. Open Google Maps, click on your location, then right-click to display the coordinates at the top.
   2. Once you have your coordinates, update the code with your location and set a reasonable radius, such as 10 meters.
   3. The geofence radius in the code is set to 0.00005 degrees, which translates to about 5.57 meters (18 feet) in real-world distance. Since one degree of latitude is approximately 111,320 meters, multiplying by 0.00005 gives this small radius.
   4. With such a small geofence, even a minor misclick on Google Maps—like selecting the house next door—could place the user outside the safe zone immediately. Increasing the radius slightly could help avoid these issues.
6. To test the geofence capabilities, move the GPS module around to simulate movement and observe how the system responds to the geofence. 
   1. Geofence Alert:
      1. If you move outside the geofence area, the buzzer should activate.
      2. If the buzzer doesn’t sound when crossing the geofence boundary, check the geofence_lat, geofence_lon, and geofence_radius values that you entered are correct.
   2. Inside the Geofence:
      1. When within the geofence area, the buzzer should turn off.
7. The OLED screen should display:
   1. Temperature (°C) – accurately updates in real-time.
   2. If the OLED does not display correctly, check wiring connections for the display.
8. Now that we've confirmed everything works, here is the full code!
   1. This code integrates all the components you've set up, including MQ135 gas sensor, GPS module, temperature sensor, pulse sensor, and OLED display. It continuously reads data from these sensors and displays relevant information on the OLED screen while also triggering alerts based on certain conditions.
   2. What the code does:
      1. Monitors air quality using the MQ135 gas sensor.
      2. Retrieves GPS coordinates using the GPS module and checks if the location is within a predefined geofence.
      3. Measures temperature with the Dallas Temperature sensor.
      4. Reads heart rate signals from the pulse sensor and flashes the onboard LED.
      5. Displays this information on the OLED screen.
      6. Triggers a buzzer if the device moves outside the geofenced area.
   3. Try modifying these settings:
      1. Adjust sensor thresholds:
         1. Change Threshold = 580; for the pulse sensor to see how sensitive it is to detecting a heartbeat.
         2. Modify geofence_radius = 0.00005; to change how far the device can move before triggering the geofence alert.
         3. Adjust the gas concentration warning level in the display logic (gasConcentration > X) to make it more or less sensitive.
      2. Customize alerts:
         1. Change the buzzer frequency or duration in playTone(int frequency, int duration) to make different alerts for different situations, such as it getting louder the further away the astronaut is or, the longer they are outside the geofence.
         2. Add a warning on the OLED display if temperature exceeds a certain value (e.g., if (tempC > 30) display a "High Temp!" alert).

      3. Add more data to the OLED display. Currently, the OLED screen shows temperature, gas levels, acceleration, and GPS data. You can modify it to:

         1. Display heart rate data if above a threshold.
         2. Add warnings for high gas concentration or extreme acceleration.
         3. Show a countdown timer for when the next GPS update occurs.

Troubleshooting tip: if things aren't working as expected, check your wiring! That is where most issues arise.

Wearability

To make your device wearable, follow these steps:

1. Place your device in a box or container.
   1. This can be cardboard or plastic. But note that whatever box or container you use you'll want to be able to see the OLED display and have easy access to any switches.
   2. Once the electronics are secured in the container, close it.
2. Attach the velcro straps around the container.
3. Attach velcro straps to whichever item you wish to wear the device on, such as a sweatshirt.
4. Now you're all set to wear your personally made device with pride!