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T-200 thruster lose thrust power when underwater

Hi guys!

I’m testing the behaviour of the T-200 thruster using different propeller models in order to determine the most efficient one. I can’t obtain results because the T-200 behaviour when underwater is very weird. I send a servo.write command from 1500 to 1900. During this process I read the thruster current consumption. The current consumption and the thrust of the Thruster increases until it reaches 1600. At this point the current consumption and the thrust from the T-200 remains fix although orders of over 1600 are sent.
This weird behaviour appears only when underwater, if I perform the same experiment in the air the T-200 shows a normal behaviour.

I add two videos to show the problem:

  1. underwater test
  2. air test

Anyone know what might be happening?
Thanks for the advance

Hi @amt132,

What kind of ESC and power supply are you using? How do you have everything connected up/what wire gauge and lengths do you have for power to the ESC and ESC to thruster?

-Adam

Hi @adam,

I’m testing the behavior of the T-200 thruster with @amt132. Therefore I will answer your questions below:

  • We are using the Afro 30A Race Spec Mini ESC w/BEC.

  • We have used 3 types of powe supply: LiPo battery 2200 mAh - 3S - 45C, car battery 12V and adjustable switching power supply.

  • Below I attached some images how I have everything connected:

Thanks,

Additionally, I share a graph where you can see you can see the current limitation vs. pwm:

From 1530 to 1590 uS describe the same trace as your graph, but past the 1600 there is something that limits the current.

best regards

We will be waiting for your answer as soon as possible.

Can you post your Arduino control code generation the PWM signals here? Have you altered the firmware on the Afro ESC is any way/what firmware are you running? What is the current capability of the power supply you have used to test? Something is limiting the thruster output, and it is either your control signal, ESC firmware/settings, or power supply.

-Adam

Hello,

I’ve tried several codes with different libraries. I share two codes:

#include <Servo.h>

Servo ESC;
int signal;
/*****************
Setup
******************/
void setup()
{
ESC.attach(9, 1100, 1900); //attach(int pin, int min, int max)
//ESC.attach(9); //attach(int pin)

ESC.writeMicroseconds(500);
delay(5000);

Serial.begin(9600);
Serial.setTimeout(10);
}
/*****************
Main loop
******************/
void loop()
{
while(1)
{
signal=1500
ESC.writeMicroseconds(signal);
delay(20);
}
}

And another code:

#include <Servo.h>
#include <ESC.h>

ESC myESC (9, 1100, 1900, 500);
int oESC=1700;
/*****************
Setup
******************/
void setup()
{
myESC.arm();

Serial.begin(9600);
Serial.setTimeout(10);
}
/*****************
Main loop
******************/
void loop()
{
while(1)
{
myESC.speed(oESC);
}
}

I haven’t altered the firmware. The Afro ESC have the factory configuration. The test has been done with two different Afro ESCs.

In addition, I used a NAZE32 flight controller and a 20A Race Spec ESC to control the Thruster T200:

But the problem persists.

The power supply can provides 20A. I did the test with a LiPo battery, 12V car battery and power supply, but the T200 behaviour was the same.

There is some way to know if the Thruster T200 is broken?

Thanks for your support @adam.

@tfm889,

Brushless motors are very simple devices, if the motor is spinning smoothly and consistently then it is fine. I suspect the issue is with the ESCs you are using, what firmware does the second ESC you tried run? If it is BlHeli, you should disable “Low RPM Power Protect”, that would cause this sort of behavior. I believe there may be a similar issue with the first, but the SimonK firmware on the AfroESC is a bit more difficult to alter unless you compile your own, or you flash ours. The old Basic ESC R2 used to be based on that ESC, and we used the linked firmware.

-Adam