ZTW Seal 150A ESC starts up in wrong direction

[IowaNav]

Hi all,

I've been working on an amphibious vehicle model to be used for research at my University. The thing is more robot than RC boat at this point, but many of my parts have been sourced from OSE. I've got a number of questions I'll be putting on the forum over the next few days, as we've been having some issues with crosstalk between servos, surging of our waterjet drive motor, etc. For now, I'd like to focus on the drive-wheel controllers.

I've got two ZTW Seal 150A ESCs driving two rear wheels via gearboxes. Both share identical programming, receive identical PWM inputs, and are connected to identical motors. However, one of the ESCs will occasionally (about one time in five) start up rotating in the wrong direction. For example, given a slow forward throttle command, the port side wheel will rotate forward at a slow speed. The starboard side wheel will rotate backward for about 1 second, stop, and then begin rotating forward.

It will also occasionally "blip" into reverse when a constant forward throttle position is being commanded.

I've switched motors, switch ESC throttle leads, swapped phases on the motor leads, etc. The behavior always tracks that particular ESC.

Anything else I can try? Or should I just keep badgering ZTW for a warranty replacement?

[Panther6834]

For the connection between the ESCs, and the receiver, I assume you are using a Y-harness (ie. one end has a single male connector that plugs into the receiver, while the other end has 2 female connectors that you plug the ESCs into). In regards to the Y-harness, the 'leg' going to the receiver has 3 wires (the first two being red & black, with the third usually being white, yellow, or brown). As for the other end (the ends that the ESCs plug into), does each leg have 3 wires...or, does one of those legs have only two (black & white/yellow/brown...ie. NO red)?

If all three 'legs' have 3 wires, that could be part of the problem, as one of the tattoo 'legs' that the ESCs connect two should ONLY have two wires (black, and white/yellow/brown). If both ESC 'legs' have three wires, snip the red wires on one of them. The red wire is what supplies power to the receiver, and, thus, to any other connected devices (such as servos). You ONLY want one ESC providing power to those. If both ESCs are providing power to the receiver, that can (and usually does) lead to problems.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

[IowaNav]

Hi Panther6834,

Thanks for the reply.

First, I should clarify the setup a little bit.

I have a total of three servo "banks" as I'm calling them. Each bank is powered by a separate BEC (Castle CC BEC 2.0 WP) to spread the load of some of the larger servos. The banks consist of shared 6V and ground rails, plus two rows of jumpered header pins. This allows me to power servos using external BECs and completely decouples the power from the signal wires. None of the ESCs have built-in BECs.

My RC receiver is powered from one of these servo banks. I have customized the receiver setup to allow me to drive the vehicle over multiple redundant radio links, or from a laptop, but it boils down to Rx -> SBUS out -> Arduino-based microcontroller -> PWM outputs. The PWM outputs are bundled together and run to the respective servo banks to command the servos/throttles/relays, etc. This setup, while it sounds confusing, consolidates all of the wiring.

Since I've got, essentially, an RC boat married to an RC car, with some additional servos used to retract the wheels, I'm dealing with a lot of signals going back and forth. Everything in the boat has a shared ground. To control a servo at the stern of the boat, I have only to run a single signal wire (no red or black) from the microcontroller+receiver to the correct column on the servo bank. I can therefore bundle all nine signal wires going to the stern into a single shielded cable to save space and keep things more orderly.

So, back to your reply. I have a sort of Y-harness, but it's one that I crimped myself. Both ESCs share a single signal wire. The red and black wires are connected to the positive and ground pins on the servo bank. I wasn't sure whether the red wire actually does anything on an opto ESC, but I left it connected just in case.

I'm also certain that this behavior of the ESC has nothing to do with the complexity of the receiver and signal chain. Even with the drive-wheel ESCs connected directly to the receiver, one of them still starts up in the wrong direction about 20% of the time.

[Panther6834]

Got ya. In that case, scratch my earlier comment.


~ More peace, love, laughter, & kindness would make the world a MUCH better place