I’ll start off by stating that I am very new to this. I am trying to connect additional servo motors to the BlueROV2 but I am not sure where to start. I want to use a Dynamixel motor but I am confused as to how I can connect the motor to the RPi that is onboard in the electronics enclosure. I’ve noticed that BlueRobotics sells wetlink penetrators (https://bluerobotics.com/store/cables-connectors/penetrators/wlp-vp/) for additional connections to replace the blanks, but it doesn’t seem to include the black waterproof tube that comes with the thrusters, making the wires leading out of the enclosure to the motor prone to water damage and also not fully sealing the enclosure from water. And then after I accomplish that, how do I access the Raspberry Pi without removing it from its place in the enclosure?
Can anyone help me or point me towards a video that allows me to safely attach a new motor to the electronics enclosure and program it with the onboard raspberry pi?
Hi @Dhruv -
Happy to help! It’s worth noting that dynamixel servo motors do not seem to be rated for use underwater, at significant depth. I would guess the IP68 rating, 30 minutes at 1-3 meters, would not work for your application!
As you also note, the typical servo cable does not have an outer jacket, and would not be compatible with the WetLink Penetrator.
You’ll have better luck with a servo rated for underwater use - we’re working on launching or own, but in the meantime this is a great alternative!
As for controlling the servos with the Raspberry Pi, you can simply connect them to additional channels on the Navigator - Most are used to control the ESCs, lights, and camera tilt, but the other channels can be configured to control servo motion via joystick buttons easily, and you can control up to three servos via this ArduSub approach easily!
Welcome to the forums, let us know if you get stuck on your project at any point!
Thank you so much for the welcome and quick reply! I should’ve been more specific; I have made a sealed container for the dynamixel to be in for initial testing, because I just wanted to control a motor just as proof of concept, but thank you for the servo suggestion! I did come across some PUR cables that are sold by BlueROV (https://bluerobotics.com/store/cables-connectors/pur-subsea-cable/) but I’m not sure whether that can be used for any component outside of the bluerobotics family. This question remains even for your servo suggestion, because even though that servo is rated for depth, I assume it would still need to be connected through one of the blank penetrators (which are replaced by the wetlinks?) Sorry if this is a dumb question but I’m just trying to wrap my head around connecting anything into the electronics enclosure.
Hi @Dhruv -
No big deal! The cable you link is intended to be used with WetLink Penetrators, that’s correct. You can connect the end of the cable on the outside of your enclosure to your devices, but making sure this joint is water-tight, so water doesn’t leak along the cable, through the WetLink, and into your housing is critical! If you already have an enclosure, you could use an additional WetLink penetrator to bring the cable into it?
Hey @tony-white,
Thanks again for your response. I’m just wondering whether the only way to connect a motor to the electronics closure is with the penetrator + cable combo? Also, there are three different cables being sold, and among those I’m unsure as to which one will be best suited for running a motor – the power/ethernet one or the gripper one?
Once I pick a cable, you’re saying that I can use the wires that come within the cable itself to connect to a motor driver which will then control the motors? I’m not really sure, but could you please walk me through how you would connect the BlueTrail servo you mentioned the ROV? Thank you for your time.
Hi @Dhruv -
No problem.
The WetLinkPenetrators can be used with a variety of cable sizes. You would select the correct one for the cable you choose based on the outside diameter of the cable - the Technical Details section of cable products also lists/links the appropriate penetrator to use.
The Servo I linked is powered by 4.8 to 7.4 V, DC. It also comes with a Cobalt Connector on it, so the intention is to use a cobalt cable and bulkhead connector to bring it into your enclosure. It is likely possible to order this Servo with different connector / cable output options. If you didn’t use this connector, you would presumable have a cable coming from the unit that can be stripped back to reveal the three conductors - power, ground, and PWM signal. This cable could be brought into your housing with a WetLink penetrator, and connected to the appropriate voltage, with the signal wire connecting to one of the PWM outputs of your Navigator or control device.
The gripper cable would be most appropriate if you were using your own cable, but this is likely not necessary if you get the Servo to already come with a cable!
The Servo does not require a motor driver! Just a servo-style PWM signal and the low voltage. Brushless DC motors like the T200/M200/M500 use an ESC, which takes in this servo-style control signal and battery voltage, and then drive a brushless motor via a 3 wire cable (where all wires are for power.)