• Mech Update #04

    Erin RobotGrrl2 days ago 0 comments

    Preliminary results of the magnetic servo movement coupling test are here:

    The concept works. Here you can see the servo moving inside the enclosure, while a piece outside the enclosure is also moving.

    The hypothesis was that this type of coupling mechanism would be strong enough to hold the buoy to the reel underwater, overcoming the buoyancy force, water currents, and the splash-down into the water.

    HOWEVER, The observations with this test do not support the hypothesis. The coupling strength between the internal and external piece is weak. Minor resistance permits the piece to lose connection.


    The original test that supported this as an idea to test was sticking two magnets to each other between the polycarbonate enclosure, which provided a strong connection. The setup in this test differed from the original test in that there's additional separation distance between the magnets due to the material thickness and air gap between the pieces.

    What could have been improved about this test? The result could have been arrived at sooner. The prototype should have been made out of cardboard and hot glue. Getting too caught up in the iterations of the curvature of the bottom of the enclosure invested too much time in design and fabrication.

    The next steps are to contemplate these observations and figure out ways of trying to improve the strength of the moving pieces. If no improvement is found, then it's time to move to a different release mechanism. Likely within the constraints of this enclosure. One idea could be a very strong electromagnet that would trigger a latch.

    This is a quick update post to share these results. Over the past few days has been a lot of tedious effort on iteration of those two pieces. Will share all the photos of that in a project log later.

    Here's an extra observation. In slow motion, you can see how the movement of the external piece 'catches up' to the internal piece. Interesting!

  • Onboard Gateway - Schematic and PCB Design

    Leonardo Ward4 days ago 0 comments

    The electronic design for the Onboard Gateway will contain the following main components:

    • ESP32 DEVKITC 32D
    • RFM95W (LoRa)
    • USB LiIon LiPoly Charger Board (3.7V 1 Cell Battery Charger)

    Once we selected the main components we created a schematic and designed the PCB.

    Schematic

    Bill Of Materials

    QuantityNameDescription
    1RFM95W LoRa RadioLoRa Module
    1ESP32-DEVKITC-32DESP32 Module
    1USB LiIon/LiPoly charger1 Cell 3.7V Battery Charger
    2TERM BLK 2P SIDE ENT 5.08MM PCBBattery Connector, and External Power Source
    1CONN HEADER R/A 2POS 2.5MM
    Battery Connector
    2CONN HEADER VERT 40POS 2.54MMMale Headers
    1CONN HDR 2POS 0.1 GOLD PCBConnector for the Battery Charger
    1CONN HDR 3POS 0.1 GOLD PCBConnector for the Vin Selector (5V or USB for the ESP32)
    1CONN HDR 5POS 0.1 GOLD PCBConnector for the LoRa Module
    1CONN HDR 6POS 0.1 TIN PCBConnector for the Battery Charger
    1CONN HDR 9POS 0.1 GOLD PCBConnector for the LoRa Module
    2CONN HDR 19POS 0.1 TIN PCBConnector for the ESP32
    1CONN JUMPER SHORTING .100" GOLDVin selector for the ESP32
    1GPS AntennaGPS Antenna
    2LoRa and GSM AntennaLoRa and GSM Antenna
    1CONN HDR 16POS 0.1 TIN PCBConnector for the ESP32 (to use the other available pins)
    1CONN HDR 12POS 0.079 GOLD PCBConnector for the ESP32 (to use the other available pins)

    PCB Layout

    3D Model

  • ​Onboard Gateway - Electronic Components

    Leonardo Ward4 days ago 0 comments

    The buoy transmits its position using LoRa, therefore it is necessary to create a device that the fishers can carry with themselves that receives the position data (using LoRa). This devices also creates a WiFi network and streams the data through it, a phone will be used to access this local network and visualize the data (using an app).

    Similar to the buoy design, we considered different alternatives that were able to meet the requirements and then selected the best one, and selected the most appropriate ones.

    Main Components

    • Microcontroller: we selected the ESP32 DEVKITC 32D as the breakout board for this project because we need to create a local network and connect to external ones (WiFi). Similar to the buoy, we can have Over The Air (OTA) updates. Relevant alternatives that were considered: the LOPY IOT DEV BOARD.
    • Communication: we selected the RFM95W LoRa Radio because it provides an acceptable coverage and the technology facilitates the creation of a network were different buoys are streaming their position. 
    • Battery Charger: we selected the USB LiIon/LiPoly charger. All the boards in the design can work with 3.3V, a 1 cell Battery (3.7V) will power the device. This breakout board was selected because it connects to the battery and the load. The board will charge the battery if it detects an external power source, and also power the load using the battery. Relevant alternatives that were considered: the USB / DC / Solar Lithium Ion/Polymer charger.

  • Buoy B - Schematic and PCB Design

    Leonardo Ward4 days ago 0 comments

    The second electronic design for the buoy (Buoy B) will contain the following main components:

    • ESP32 DEVKITC 32D
    • Ultimate GPS
    • TB6612FNG
    • Servo connection
    • RFM95W (LoRa)

    Once we selected the main components we created a schematic and designed the PCB.

    The main characteristic that differentiates the design of Buoy A and Buoy B is that the first one contains the GSM module, and second one doesn't have it. 

    Schematic

    Bill Of Materials

    QuantityNameDescription
    1Adafruit Ultimate GPSGPS Module
    1RFM95W LoRa RadioLoRa Module
    1ESP32-DEVKITC-32DESP32 Module
    1TB6612FNG MOTOR DRIVER BOARDMotor Driver
    1TERM BLK 2P SIDE ENT 5.08MM PCBTerminal Block for the DC Motor
    1TERM BLK 3P SIDE ENT 5.08MM PCBTerminal Block for the Vin, 5V and GND
    1CONN HEADER R/A 3POS 2.5MM7.4V 2 cell Battery Connector
    2CONN HEADER VERT 40POS 2.54MMMale Headers
    1CONN JUMPER SHORTING .100" GOLDVin selector for the ESP32
    1GPS AntennaGPS Antenna
    2LoRa and GSM AntennaLoRa and GSM Antenna

    PCB Layout

    3D Model

  • Buoy A - Schematic and PCB Design

    Leonardo Ward4 days ago 0 comments

    The first electronic design for the buoy (Buoy A) will contain the following main components:

    • ESP32 DEVKITC 32D
    • Ultimate GPS
    • TB6612FNG
    • Servo connection
    • RFM95W (LoRa)
    • SIM7600CE-T (GSM/GPRS)

    Once we selected the main components we created a schematic and designed the PCB.

    The main characteristic that differentiates the design of Buoy A and Buoy B is that the first one contains the GSM module, and second one doesn't have it. 

    Schematic

    Bill Of Materials

    QuantityNameDescription
    1Adafruit Ultimate GPSGPS Module
    1RFM95W LoRa RadioLoRa Module
    1ESP32-DEVKITC-32DESP32 Module
    1TB6612FNG MOTOR DRIVER BOARD
    Motor Driver
    1TERM BLK 2P SIDE ENT 5.08MM PCBTerminal Block for the DC Motor
    1TERM BLK 3P SIDE ENT 5.08MM PCBTerminal Block for the Vin, 5V and GND
    1CONN HEADER R/A 3POS 2.5MM7.4V 2 cell Battery Connector
    2CONN HEADER VERT 40POS 2.54MMMale Headers
    1CONN JUMPER SHORTING .100" GOLDVin selector for the ESP32
    1GPS AntennaGPS Antenna
    2LoRa and GSM AntennaLoRa and GSM Antenna
    1SIM7600CE-T 4G(LTE) Arduino ShieldGSM/GPRS Module


    PCB Layout

    3D Model

  • Firmware setup process

    Oluwatobi Oyinlola4 days ago 0 comments

    The bouy system consists of five parts:

    • Motor controller
    • Ultimate GPS
    • ESP32
    • LoRa RFW95
    • SIM7600 (GSM Modem)

    We have finally decided to go for ESP32 for the firmware interface for both the bouy and the onboard gateway.

    This is an ultra-low-power solution designed for IoT applications because of its low power with a transmitting power of +12dBm.

    For the purpose of our solution, we shall develop all the firmware on the ESP and the memory will be enough to serve for the Bouy and onboard gateway.

    During the design, we shall develop the firmware code on Arduino IDE for coding flexibility among the team and for quick debugging.

    The first test process is to check the network connection by interfacing the ESP with the GSM modem and enable the connectivity and then implement the GPS directly to the bouy.

  • Intelligent Buoy - Electronic Components

    Leonardo Ward4 days ago 0 comments

    The intelligent buoy requires position marking and communication. To accomplish those goals, we evaluated different alternatives and selected the main components in the design. 

    For the first prototype we mostly selected breakout boards to perform the proof of concept as soon as possible.

    We considered different alternatives that were able to meet the requirements and then selected the best one, because of its features or the cost (we want to design low cost solutions).

    Main Components

    • Microcontroller: we selected the ESP32 DEVKITC 32D as the breakout board for this project because we wanted to perform Over The Air (OTA) updates. Having OTA can reduce the times that the buoy needs to be opened to access the electronics. The buoy needs to be waterproof, and will be sealed. Relevant alternatives that were considered: the LOPY IOT DEV BOARD.
    • GPS: we selected the Adafruit Ultimate GPS. We found that it has been used before in buoys for position marking in the Open Source Ocean Data Buoy Project and the Drifting Buoy Project.
    • Communication: we selected the RFM95W LoRa Radio because it provides an acceptable coverage and the technology facilitates the creation of a network were different buoys are streaming their position. 
    • Motor Controller: we will test servo motors in the release mechanism, and the ESP32 can create the required PWM. We also added the TB6612FNG MOTOR DRIVER BOARD as a backup plan, in case we need to use a DC motor instead of the servo motor.
    • GSM/GPRS: we selected the DFRobot SIM7600CE-T 4G(LTE) Arduino Shield because of its global coverage and the possibility of incorporate 4G GSM at a relative low cost.

    Considering the size of each board we realized that the SIM7600CE-T will probably exceed our width limits inside our current design of the buoy. Therefore, we decided to create 2 designs: the PCB Buoy A will contain the GSM board, and Buoy B won’t have it. 

  • Mech Update #03

    Erin RobotGrrl5 days ago 0 comments

    The servo fits and the magnetic coupling attaches:

    Here is what the CAD assembly of the 5 separate 3D printed pieces looks like:

    Read on for more about the tweaks needed and next steps!

    Read more »

  • Mech Update #02

    Erin RobotGrrl08/02/2020 at 06:24 0 comments

    This update is all about iterating the servo block assembly. The servo block will be inside of the intelligent buoy enclosure (Nalgene bottle). It needs to be attached with magnets to the rest of the stages because the dimensions are too small for a direct attachment.

    Decreasing the size of the servo block assembly was iterated on 3 times since the last update.

    Read more for CAD screenshots and photos of the 3D print!

    Read more »

  • Information about Sleeve Bearings

    Erin RobotGrrl08/01/2020 at 21:32 0 comments

    It's likely we'll be using a sleeve bearing made from HDPE in the rope spool box. It was interesting to see design of these is somewhat like an art. Check out this project log for my research notes! 

    What are sleeve bearings? This presentation is useful review.

    [source]

    Read on for more of my notes!
    Read more »