Part overview

Mainboard - ROV

The ROV main mainboard connects most of the components together. It is a custom design. 

The jumpers are used to disable the stepper drivers.

Connections

Mainboard gets power from "Dual Voltage supply - ROV"
The connection is located on the backside of the PCB.

Reference

Electrical schematics

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. 

Teensy for sensors

This teensy is gathering data from various sensors and sending data to RPi.
Sensor Teensy is running this code. 
Sensors connected:
 - Echo sounder
 - Pressure sensor
 - Leak sensor
 - IMU

Reference

Getting started guide

Teensy 4.0 Documentation

Stepper Driver Polulu DRV8825 (md20b)

A stepper driver is used to control a stepper motor. Teensy is controlling the Drivers.
There is one driver for each stepper motors. (2 in total)

VREF is configured to 0.70V which corresponds to 1A/stepper phase.

Electrical Connection

Electrical Drawing -> Stepper Diagram

Reference

Pololu Guide and docs

Leak sensor

Leak sensor detects water leak in the electronics tube.
The sensor is connected to sensor teensy.

Reference

Blue Robotics Guide and Docs - Chip

Blue Robotics water probe

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

Adafruit IMU docs

Temperature sensor 

This sensor is planned to measure the internal temperature of the ROV. Two sensor is planned, one for each side. 
Both PCB has ready holes for the sensor. Sensor is not currently mounted or bought.
Code is not edited to support the sensor, but should not be hard to implement.
The purpose of this sensors is to check if the tube is overheating. 

Model: DS18B20 

Reference

digikey DS18B20 store and docs

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

Raspberry pi 4

Raspberry pi 3B+

Camera

Model: Low-Light HD USB Camera

This camera is not yet in use. Older unknown camera is connected to RPi, and works (poorly) through realVNC.
New cameras is bought, but not tested.
The plan was to use servo for controlling camera angle. (this is implemented in code)

Blue robotics have 3D models for mounting bracket on this website.

Reference

Blue Robotics camera Guide and Docs

LED Lights

LED lights illuminates underwater for the camera.
The lights are not currently mounted.
Previous plans was to control the lights from RPi.
Code is already implemented. 

Input Voltage: 10-48V
Controlled with servo PWM.

NOTE: High power draw! up to 60W,

Reference

Docs and guide

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

Blue Robotics Guide and Docs

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

botblock.io Guide and Docs

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

The interface box is lost. 

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. 
A stepper motor is connected to a stepper driver.

Model number: 17hs19-1684s-pg100

Electrical Connection

See Mainboard → Connections

Datasheet

Torque Curve

Magnetic sensor

Magnetic sensor is a switch that closes when nearby to a magnet. 
One is used in each motor house for calibration.
Output is on/off like a normal switch.

Reference

no.rs proximity sensor

Adafruit Ultimate GPS

The GPS module is inside the suitcase. It is connected to RPi with USB through a Serial to USB converter.

Reference

adafruit.com/adafruit-ultimate-gps

USB2Serial

Is converting serial data from GPS into USB.

Dual voltage converter - Surface

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

toggle switch SPDT 5A

trimpot 12kohm 0.25W

Dual voltage converter - ROV

This is a voltage converter located inside the ROV. It has a connector on the backside to power the mainboard.

INPUT Vin: 46V from the Tether cable.

OUTPUT: 5V and 12V with different types of connections.

Warning: 5V does not work with very small loads. ex. connecting only one microcontroller will not work.

Reference

UWE 48 -> 12V  (black)

TEN 25-2411WI (pink)

DS18B20

Electrical schematics

I2C Level Converter

For i2c devices with different voltages. 

Not used. Old system used arduino with 5V I2C logic. Teensy use I2C 3.3V logic.
All i2c sensor in ROV uses 3.3V.

Reference

https://bluerobotics.com/store/comm-control-power/tether-interface/level-converter-r1/