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Brushed thrusters with BlueROV2 system


(Altum Operations) #1

To Whom it May Concern,
We are a team competing in the Navigator level at the Monterey Regional MATE competition. We are using the “standard” electronics package for the ROV. We were not able to obtain brushless motors due to cost, so we settled for six bilge pump motors.
For motor drivers we are using Dimension Engineering Sabertooth motor drivers. https://www.dimensionengineering.com/products/sabertooth2x5

Our question is this: What mode would be better to use with the BlueROV2 system?

There are different modes in which the motor drivers can be used. They are as follows:
Analog, R/C Input, Simplified Serial, and Packetized Serial.
This is what it says about Simplified Serial:


Mode 3: Simplified serial.
Simplified serial mode uses TTL level RS-232 serial data to set the speed and direction of the motor. This is used to interface the Sabertooth to a PC or microcontroller. If using a PC, a level converter such as a MAX232 chip must be used. The baud rate is set via DIP switches. Commands are single-byte. There is also a Slave Select mode which allows the use of multiple Sabertooth 2x10 from a single microcontroller serial port.

This is what it says about Packetized Serial:

Mode 4: Packetized serial
Packetized serial mode uses TTL level RS-232 serial data to set the speed and direction of the motor. There is a short packet format consisting of an address byte, a command byte, a data byte and a 7 bit checksum. Packetized serial automatically detects the transmitted baud rate based on the first character sent, which must be 170. Address bytes are set via dip switches. Up to 8 Sabertooth motor drivers may be ganged together on a single serial line. This makes packetized serial the preferred method to interface multiple Sabertooths to a PC or laptop. Because Sabertooth uses the same protocol as our SyRen single motor drivers, both can use used together from the same serial master.

Thank you for your time.
Sincerely,
Tobin Cox
Electronics and Software engineer of Altum Operations


(TCIII) #2

@Altum_Operations,
The Pixhawk that is used to control the BlueROV2 internal ESCs outputs a R/C PWM signal that varies from around 1000us (full reverse) to 2000us (full forward) with 1500us being neutral or stopped. Therefore you might want to consider using the Sabertooth’s R/C input.
Regards,
TCIII AVD


(Rusty) #3

Hi @Altum_Operations,

ArduSub and the Pixhawk are set up for use with standard RC input control. I would strongly recommend going with that method.

-Rusty


(Altum Operations) #4

Thank you! We will try that.