Vimy Electrical Overview

Vimy's electronic system was designed to complete the 2016 MATE contract. Although it was very well designed and implemented. There are modifications that need to be made during the 2017 design cycle. In this guide, we walk through Vimy, and talk about changes that need to be made.

System Integration Diagram

The following SID displays an overview of the entire electronic system of BP. Take time to familiarize yourself with this diagram, as it is an excellent reference for future system design.

ROV Communication Diagram

Each Component

For now, until things become better organised, each component will be a subheading on this page. It's gonna get messy, but that's life.

48/12 DC-DC Converter

BP employs three DVQ0135V2NBSC DC-DC converters (available on Digikey) to reduce the 48V that travels down the tether to the ROV.

Pinout

Info

• V_in = 36 - 72V. We use 48V, see system brownouts below 36V.
• P_out goes up to 420W. In practice, we only need two DC-DCs to function, third is for redundancy
• Addressable and can be communicated with over a SMBus protocol. This was never implemented on BP, but is desired. See Issue 34.
• Difficult to properly solder. Pin 2 and 4 must be tied together, as well as pins 16 and 6. A circuit board was created to deal with making these connections. This board must be updated if PMBus addresses are to be implemented.

Motor Controllers

The Sabertooth 2x5 motor controllers are employed to control the camera rotation DC motors using 12V input voltage and micro controller data signals. The extrenal lights are also powered by a motor controller channel. Our implementation of interfacing the motors can be found here.

Pinout

The pins are initially a little confusing on this device. They are as follows:

• B+/B-: "Battery" input. We put in 12V to B+, GND to B-
• GND: Microcontroller Ground. We attach GND
• 5V: A locally created 5V for powering the onboard microcontroller. DO NOT attach it to anything
• S1/S2: Control inputs for each motor channel
• M1A/M1B/M2A/M2B: The differential motor outputs, as controlled by S1 and S2.

Settings

On the 2x5s, you'll see 6 switches. In 2016, we chose to use RC control because it's the same as the input the ESCs take. See Issue 22 for a past treatment of this.

• Switch 1 & 2: Sets the input mode of the motor controllers. We use RC mode, obtained with 1=OFF, 2=ON
• Switch 3: Lithium Cutoff Enable: When OFF, the switch will shut the motor controller down if it does not receive the proper voltage when running on Lithium Ion Batteries. Should be ON.
• Switch 4: Mixed or independent motor control mode. We use independent, achieved with 4=OFF
• Switch 5: Linear/Exponential Response. We use linear, achieved with 5=ON
• Switch 6: R/C Mode/Microcontroller mode select. We had problems last year with microcontroller mode, and use R/C mode.

Connections

In BP, the connections are made as follows:

• Motor Controller 1 Channel 1 -> FWD Camera (Brown Wires from motor whip)
• Motor Controller 1 Channel 2 -> AFT Camera (Green Wires)
• Motor Controller 2 Channel 1 -> Tool motor (Disconnected)
• Motor Controller 2 Channel 2 -> Lights (Blue Wires)

Electronic Speed Controllers

Right now, Vimy uses 6 ESCs to control each of its Blue Robotics T200 Thrusters. These are brushless DC motors, and need a 3 phase AC signal created by the ESCs. The ESCs each take in a separate PWM signal, implemented in software here. There are options to address these ESCs with I2C in the future (or the past 😛) , as discussed in Issue 9.

Pinout

The pinout for these devices is simple.

• The Red/Black Wires on the side with the Servo wire input takes 12V/GND.
• The Servo wire input takes in the PWM control signal from the Maestro
• The Red/Black/Yellow wires on the other side of the ESC connect to the T200. In our implementation, connect T200 Green to ESC Red, T200 White to ESC Yellow, T200 Blue to ESC Black