Brushless motors for Underwater robot

Using Arduino Project Guidance
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Hi, i'm really new to this.
I'm currently building an under water robot to survey under the water. At the moment i have these components.
Brushless motor: Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - Hobbyking
ESC: Radio Control Planes, Drones, Cars, FPV, Quadcopters and more - Hobbyking

I connected these up with some code i found online with the arduino and a potentiometer. But now I am having some problems. So i have a few questions.

  1. Are there any tutorials online? I can't get my head around the code, i've done a bit of python, but thats it.
  2. Is there anyway that i can set this motor to go reverse or forward when the joystick is in different positions?
  3. Can i just solder four esc cables into one?
  4. Can the power run along an ethernet cable?

Thanks in advance

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I've built an RC plane from Arduinos and brushless motors so I might be able to help.

  1. You listed your motor and ESC but you didn't mention what battery you are using. Using the correct type of battery makes a LOT of difference!!!!

zacmortimer:

  1. Are there any tutorials online? I can't get my head around the code, i've done a bit of python, but thats it.

^ Can you post your code?

zacmortimer:
2. Is there anyway that i can set this motor to go reverse or forward when the joystick is in different positions?

^ Yes! The motor and ESC should be 3 phase, so there should be three inputs to the motor (and three outputs from the ESC :slight_smile: ). If you mess around and interchange the connections, you will find a combination that will reverse the direction of the motor. Don't worry, there is no "correct" or "incorrect" way to wire a brushless motor (except with respect to the expectations of your specific project).

zacmortimer:
3. Can i just solder four esc cables into one?

^ Wait, what? What exactly on the ESCs are you trying to solder and WHY?

zacmortimer:
4. Can the power run along an ethernet cable?

^ I'm not sure I understand what you mean. Are you asking if you can power an ethernet cable via the BEC on the ESCs?

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Power_Broker:
If you mess around and interchange the connections, you will find a combination that will reverse the direction of the motor.

That is not what he asked, is it?

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Power_Broker:

  1. You listed your motor and ESC but you didn't mention what battery you are using. Using the correct type of battery makes a LOT of difference!!!!

I have a battery, the motors and esc run fine, ive tested them, it's more coding that i'm stuck with.

Power_Broker:
2. ^ Can you post your code?

I actually haven't got any code yet.

Power_Broker:
3.^ Yes! The motor and ESC should be 3 phase, so there should be three inputs to the motor (and three outputs from the ESC :slight_smile: ). If you mess around and interchange the connections, you will find a combination that will reverse the direction of the motor. Don't worry, there is no "correct" or "incorrect" way to wire a brushless motor (except with respect to the expectations of your specific project).

I'm building an underwater submarine, so for it to go forward and back, it needs to be able to go in reverse and forward without changing any of the cables. So when the joystick is completely forward, the motor will go one way, and when the joystick is completely back, it will go another way. And when it's in the middle it will be idle.

Power_Broker:
4.^ Wait, what? What exactly on the ESCs are you trying to solder and WHY?

Just the power cables. I'll have 3 or 4 esc's so to avoid having to have more 3 batteries can i just solder these cables together?

Power_Broker:
5.^ I'm not sure I understand what you mean. Are you asking if you can power an ethernet cable via the BEC on the ESCs?

Because it will be going underwater wireless connections won't work. Can i send the power to the motors down ethernet. Or the signal cables from the esc down to the motor. Basically i'd prefer to keep as many components as i can up above the water and at the controller.

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zacmortimer:
I have a battery, the motors and esc run fine, ive tested them, it's more coding that i'm stuck with.

^ Have you been able to get the motors spinning? I can write some code to help you with that if you want. :smiley:

zacmortimer:
I'm building an underwater submarine, so for it to go forward and back, it needs to be able to go in reverse and forward without changing any of the cables. So when the joystick is completely forward, the motor will go one way, and when the joystick is completely back, it will go another way. And when it's in the middle it will be idle.

^ This may be difficult, but it is possible. The easiest way I see it is that a homemade circuit acts as an interface between the ESC and the motor via different relays. The circuit would also take in data from the Arduino. Here is the logic of the ESC-motor interfacing device:

Input to the circuit would be digital (either 5V or 0V). If the Arduino gives it a 5V, the circuit will drive a network of relays to ensure the correct connection of the 3 phase wires that will cause the motors to spin one way. If the circuit sees 0V from the Arduino, the relays will be driven so that the motors run in reverse (i.e. the 3 phase connections are electrically rearranged via relays). See the attached schematic.

zacmortimer:
Just the power cables. I'll have 3 or 4 esc's so to avoid having to have more 3 batteries can i just solder these cables together?

^ While this is possible, I wouldn't advise it. Here's why: You could EASILY discharge the battery too fast, causing the battery to either catch fire or literally explode! (especially if your battery is a LiPo). EVEN if the battery doesn't explode, you will only have a minute or so of battery life (so why not spend a little extra? :slight_smile: )

zacmortimer:
Because it will be going underwater wireless connections won't work. Can i send the power to the motors down ethernet. Or the signal cables from the esc down to the motor. Basically i'd prefer to keep as many components as i can up above the water and at the controller.

^ Ohhhh, I see now. You know the ESCs are driven like analog servos, right? All the signal they need is a PWM from the on board Arduino. No need for ETH unless the Arduino isn't on board. 20-22 gauge wire will be all you need. As for powering the ESCs, the batteries already do that.

Motor Driving Circuit.pdf (115 KB)

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The phase switching relay scheme is practically foolproof but there is one detail you should be aware of.
If you switch the relays under power, the direction reversal and resulting current could damage your ESC. The motor would not likely be damaged but if you switched the relays at full throttle, anything is possible. The point is, make sure you include a line of code to set the throttle to zero before executing the code to switch the relays. If you had a "power_on" boolean flag you set whenever you send throttle commands > zero and clear it when you set the throttle to zero, that would be even better.

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