Thruster commander - Controlling 24V Thruster

I was using the thruster commander to test a motor and was operating at 12VDC and that off course played out well. I later attempted to perform the same test with 24VDC to the motor by connecting two 12v batteries in series. The thruster commander was still connected to the first battery making sure to not exceed the 20VDC threshold. The set-up for 24volt was done according to the figure below. I believe this fried the thruster commander but not sure why. Even if the thruster commander has a 12-volt supply form one battery I am wondering if gets 24 volts due to the fact that the ESC signal cable has its negative from the 24volt supply?
In short, I have 2 questions:

  1. Should this set-up be ok or not.?
  2. is there a way to run the motor via ESC in a an ON/OFF mode meaning the motor/thruster will start running at full speed when power is turned on without having to use PWM controller?

This would likely have been OK if you had hooked the thruster commander to the other 12V battery, the one on the right side.

In general black wires represent ground and are always connected together. What probably happened here is that the +12V from the right side battery ran through the black wire of the commander power leads, to the black wire of the PWM connection of the ESC, and back to the batttery (-) through the power leads of the ESC. Probably blowing up the thruster commander at the same time, and maybe the ESC too.

So short summary: when in doubt, keep all black wires attached together.

As for question #2, I’ve never seen a brushless ESC that will do this.

Hope this helps.


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Thank you, yes I see you’re point. The ESC is ok as it handles the voltage.

tor. 21. sep. 2023, 18:53 skrev Walt Holm via Blue Robotics Community Forums <>:

Hi @SDI,

As @wholm explained, the issue here is with all three potential levels (0V / 12V / 24V) being applied to the thruster commander in different places, because of the ESC’s communication wire ground being at a different level than the power wire’s ground.

In future it likely makes sense to approach series connections like this by starting from a single battery and only connecting the highest voltage wire to any extra batteries that get added - that way the grounds are automatically all at the same level.

It’s theoretically possible for an ESC to do this, like how our Lumen lights set themselves to full power when the signal wire is connected to a fixed DC voltage supply instead of receiving a PWM signal.

That said, I’m not aware of an ESC that does that, and it’s not a feature built in to the BLHeli_S firmware that runs on our Basic ESC, so it may be something you’d need to program yourself if you want an ESC that can switch between full speed mode vs variable-input tracked mode. It does seem like a useful feature though - I’ll raise it internally in case it’s something we can add in future :slight_smile:

Hi Oystein -
There is one method you could try, with the Thruster Commander, to make it so a switch will cause attached thrusters to come on at a desired speed. If you replace the jumper on the “switch” pins with connections to a switch, and adjust the potentiometer to the desired speed, you should be set. With the switch open (off), on power up the ESC will initialize as the Thruster Commander sends it 0% throttle. When you close the switch connection, it will send the speed registered by the potentiometer.
I hope that helps!

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Thank you all for great input, as usually :slightly_smiling_face:

ons. 11. okt. 2023, 05:17 skrev Anthony White via Blue Robotics Community Forums <>:

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