Part overview
Raspberry Pi
There is two RPi in this project. One is in the suitcase, and one in the ROV.
Both is configured with realVNC server.
Password: send email to williha@stud.ntnu.no
ROV
Model: Raspberry Pi 4B rev 1.4 4GB
Suitcase
Model: Raspberry Pi 3B+
Docs
Teensy 4.0
Two teesny 4.0 is used in the ROV. Both are connected to RPi with USB.
Teensy is used instead of Arduino because it has a faster processor.
Teensy for stepper control
This teensy is for controlling both stepper motors drivers. (wings)
Stepper Teensy is running this code. NOTE. update link after merge
Teensy for sensors
This teensy is gathering data from various sensors and sending data to RPi.
Sensor Teensy is running this code. NOTE. update link after merge
Sensors connected:
- Echo sounder
- Pressure sensor
- Leak sensor
- IMU
Reference
Fathom-X Tether Interface rev2
FathomX is an Ethernet bridge between the ROV and the suitcase. This enables communication through the tether cable.
The FathomX is connected to each side of the tether. It requires only two wires for communication.
Reference
SwitchBlox Nano
This is a miniature ethernet switch.
It is used inside the ROV for communication between different ethernet devices. (RPi, Fathom-X, and Side-scan sonar)
Reference
Leak Sensor
Leak sensor detects water leak in the electronics tube.
Reference
Blue Robotics Guide and Docs - Chip
IMU
Inertial measurement unit is gathering positional data of roll, yaw and pitch.
Is connected to Sensor Teensy with 3.3V i2c.
Model: Adafruit Precision NXP
Reference
Depth Sensor
Depth sensor is measuring pressure. It is used to calculate the depth of the ROV. (Length from water surface to ROV)
It communicates with Sensor Teensy with I2C.
The sensor also has built in temperature sensor.
NOTE: Sensor looses accuracy if its wet for more than a day.
Model: Bar30 High-Resolution 300m Depth/Pressure Sensor
Reference
Blue Robotics Depth Sensor Guide and Docs
Echo ping sonar
Ping sonar measures distance to seabed.
It is connected to sensor teensy.
Reference
Docs and guide - Blue robotics Ping sonar
Side scan sonar
Model: DeepView HM680D
Reference
Specs - Deepvision side scan sonar
TODO: Find more docs and guides
Stepper Motor
Stepper motors controls the two wings on the ROV. It has a gearbox to increase torque.
Model number: 17hs19-1684s-pg100
Electrical Connection
Electrical Drawing -> Stepper Diagram
Datasheet
Torque Curve
Stepper Driver Polulu DRV8825 (md20b)
A stepper driver is used to control a stepper motor. Teensy is controlling the Driver.
There is one driver for each stepper motors. (2 in total)
VREF is configured to 0.8V which corresponds to 1A/stepper phase.
Electrical Connection
Electrical Drawing -> Stepper Diagram
Reference
Magnetic sensor
Magnetic sensor is a switch that closes when nearby to a magnet.
One is used in each motor house for calibration.
Reference
Dual voltage converter
This is a custom made voltage converter located in the suitcase. It supplies the ROV, and some components in the suitcase with power from a 12V battery.
INPUT: 12V DC. Both inputs terminals are connected together internally in the pcb. (connecting one input terminal is sufficient)
Note: Input must be 12V, because fathom-x and router is also connected to "input" power.
Input from 11V to 40V can be used if fathom and router is connected to another supply.
The i7c converter (right) can deliver much more power if input voltage is raised.
OUTPUT: 5V (left), 48V (right). Both output voltages can be adjusted with the trimpots (blue).
Switch on/off: Down (towards output) is on.
Pcb schematic was designed with easyEDA, and ordered from JLBPCB.
Five pcb's was ordered in case more was needed for other projects.
The pcb can be cut at the white line if only one side is needed.
Components
- Dc-dc converter (right): i7c-4w-008a-120v-0f1
Input: 9V to 53V DC
Output: 9,6V to 48V (adjustable with trimpot)
Max output current at 12V (input) is 2,2A
Max output current at 24V (input) is 4,5A
See datasheet for more info - Dc-dc converter (left): VMA404
Input: 4V to 40V DC
Output: 1,25V to 35V (adjustable with trimpot)
Max output current: 2,5A - Custom pcb
- 4x screw terminal 5.08mm pitch
- 2x SPDT switch
- 2x Fuse 2A and fuse holder
- Trim pot 12kohm
- Capacitors (see schematic for value)
Reference
Find drawing under towedROV -> Electrical schematics
CAD for fastening: voltage converter mount v1.step
Website: i7C4W008A120V-0F1-R
elfadistrelec.no dc-dc converter 9...53v-48v i7c-4w-008a-120v-0f1
I2C Level Converter
For i2c devices with different voltages.
Not used. Old system used arduino with 5V I2C logic. Teensy used 3.3V logic.
All i2c sensor in ROV uses 3.3V.
Reference
https://bluerobotics.com/store/comm-control-power/tether-interface/level-converter-r1/