Blue ROV test Setup

Blue Robotics Software
1

Hi! I am building the Blue ROV for our research lab and a I have a few noob questions about it. My idea is to test it first out of water to check the wiring using a Power Supply at 14V.

1- Is it fine to use a 14V power supply to test the setup out of water or with 5 meters of tether? Then we’ll buy a 4S LiPo battery probably.

2-Also, I wanted to know if it is possible to command the Blue ROV with QGC (using a XBOX joystick) connecting my PC to the Pixhawk through microUSB without using the RaspPi.

3-If I use the Raspberry Pi instead I have can use the microUSB connection with the RPi and the aux outs to power the RPi. Is this right?

4-When connecting the PixHawk with the thrusters’ ESCs, can I use the 3-pin connector provided with them or only the signal and ground pins (since the power comes from the power supply)?

Thanks!

2

Hi DFornas,

Cool! Good questions.

  1. Yes, it’s fine to use a 14V power supply and short tether for testing.

  2. Yes, you can connect the Pixhawk directly via USB for control. Are you planning to use USB in your tether? Is this just for testing?

  3. In our experience, the aux outs on the Pixhawk don’t have quite enough power for the Raspberry Pi and it will act unreliably. I would use a separate power supply (UBEC or similar) for the Pi.

  4. There seems to be differing opinions on this between Pixhawk users. I would personally recommend disconnecting the 5V power line from all but one ESC. That will power the 5V bus for any servos you might have but will prevent the 5V regulators on the ESCs from overheating.

I hope this helps.

-Rusty

3

Yes, it helps. Thanks for your quick reply Rusty!

1,3 Great!

Regarding to 2. I think that when the test setup works using the PC directly through microUSB (out of water), we will switch to use the PC to Rpi (through Ethernet) and RPi to Pixhawk (through microUSB). Is this setup right? We are won’t use the Fathom-S board because it wasn’t in store when we bought the BlueROV. Maybe we will order it in the future but now we can’t use it.

The 4 is the most confusing point for me… the ESCs have 2 inputs for power (we will power them with a LiPo battery or a temporary ground power supply) and a 3 pin connector (with power, ground and signal). As I understand you suggest to connect each signal main out pin to each ESC signal pin but all ESC grounds to a single ground out (MAIN OUT 1 -negative pin) and all ESC power pins to a single power out (MAIN OUT 1 +positive pin). Am I getting it right?

 

4

Correction. As described here Basic ESC Documentation (Old) the small red cable is an output (BEC Output), not an input so it shouldn’t be used, right? An then I should connect each yellow signal to each out of the pixhawk and also each brown ground cable to each negative out of the pixhawk for each thruster main output.

5

Hi DFornas,

You are right, the small red wire in the Basic ESC cable is a 5V output. It does not need to be connected to anything for the ESC to work.

The reason we recommend disconnecting all but one of those is because internally they are connected to a 5V linear regulator. Those regulators can actually fight against each other and overheat if they are connected together. We’ve had issues with it so I’d recommend cutting all but one.

Let me know if you have any other questions.

-Rusty

6

I think I get it now so…

  1. The RPi can be powered from the AUX OUT (not recommended), from the 5V pad on the 3DR Power Module of the Pixhawk (enough power?) or externally (your recommendation using an UBEC or similar)? Is it possible to use the Basic ESC 5V BEC output or it is also low power?
  2. The ESC PWM SIGNAL pins must go to the Pixhawk main outs signal pins and the ESC PWM NEGATIVE pins must go to the negative pins of the Pixhawk main outs. So it is enough to cut the 5V BEC OUT of the ESC if I won't use any other servo.
Is this correct?
7

@DFornas,

Yes! You are correct on both points.

The Basic ESC BEC can only supply 500 mA (and it gets very hot) so it is not sufficient for the Raspberry Pi.

-Rusty

8

Thanks! I think it is all for now. Really nice replies, now I can work with a smaller chance of burning something :wink: