Homebuilt ROVs Forum

Man i love the plans you have laid out, our set up's are so similar course you have much more going in i think.
I got my driver for the dive and surface motor, the 2 motor carriers work perfectly i get a smooth ramping of the motors forward and reverse. I have had to set a dead band range at the center of the sticks to get a stop position.
I also received 4 max485 chips for converting rs232 signals they're tiny little things not sure if i can interface em or not. We'll see.
Good work.

PROGRESS!! Finally!

Over the last few days I have been working on building my thruster test stand. I probably over engineered it a bit, but it ensures I have a reliable test time after time... I hope!
This is the rig! I have it set up to place at the edge of the pool at the local dive club. This will hopefully prevent any cavitation due to lack of water or the prop sucking in air, which is a common problem with tank tests.
I have an Arduino Uno with a LCD shield as the control center. You can also just make out an inline voltage / amp meter in the bottom right corner of the unit. I found it at HobbyKing. Unfortunately, it is visual only... maybe I can hack it to "communicate" with the Arduino... but that is a bit above my understanding at this time...
The scale I have measures to 0.1grams.
I have 3 switches and one Pot for my controls.
Switch 1 = Arduino Power
Switch 2 = ESC on/off
Switch 3 = FWD or REV
POT = speed control.
The thruster is of course the most important part of the rig! This is a 750kv motor with a 55mm ROBB prop. The Prop nut has been modified to accept the pro and the motor shaft, as well as hopefully locking to prevent spin off.
If you have any questions, let me know! If all goes well, I will get this in the water on Saturday morning. Watch this space for updates!

Sweet setup

Martin

Turns out my little thrusters push a huge amount of power! During my test, the motor drew 14+ amps in forward in 10+ amps in reverse. The thruster produced over 1.6kg of thrust in forward and 0.6kg in reverse! It was even strong enough to bend the M8 threaded rod! I am going to beef up the pendulum and try the tests again soon.

Awesome test KR. Just wondering if you've made any progress since you posted the serial killer collage, or if you are just testing. I've been watching your progress keenly, as our ROV's are similar in some ways. What was the inspiration/purpose of conducting the water tank tests? I've got so much to learn and feel I'm missing an important point. Is it to help you with the thrust vector code you were working on earlier? or is that working as hoped?

I may have, yet again, stumbled into the same issues you have experienced (I have also recently replaced a RC Plane ESC that doesn't reverse....). It just occurred to me that I'm actually sending two values to the ESC, if I use a diagonal direction on the PS2 Left Stick. I Look forward to seeing how the Arduino processes this when I get the code updated with new values, and upload it.

I must take the time to post my project, but also thank you for the inspiration.

Steve

Hey Steve,
It is nice to hear that I have been able to provide some inspiration!

Just wondering if you've made any progress since you posted the serial killer collage, or if you are just testing.

Still testing at this time... I dont have much of a work space, and I travel A LOT for work, so I am a bit behind on the build, but I find just as much enjoyment in the testing of concepts as the actual build. With the learning curve involved in building an ROV, testing each part helps me fully understand the component and the design issues associated with each part.

My professor always said, "the space shuttle wasn't built all at once!"

What was the inspiration/purpose of conducting the water tank tests?

There were two main reasons I wanted to conduct these tests.
1.) Measure the power draw (amps) that the motor pulls during full speed forward and full speed reverse with my current prop selection. Knowing this will help me chose the right LiPo batteries and allow me to calculate my run time.
When selecting the LiPo batteries, I have been reading that there is a few values that are important: Voltage, Capacity & Discharge Rate. Voltage is easy to understand, my system is largely based on 12VDC. Capacity is the number of mA per hour the pack can discharge, and the rate is how quickly the battery can send out the juice without damaging it. I haven't done the math yet, but when I do, I will let you know what I have come up with.

2.) Measure the thrust of my thruster to determine how strong my ROV will be. Because of the way I have planned on setting up my thrusters, it is important to balance the forward vs reverse thrust to make my ROV easier to control. In this test, I measured 1.6kg in one direction and .6 in the other. With this data, my next step will be to balance the thrust via code, so that I have equal thrust in both directions. This will mean of course that I will not be using my thrusters to their full ability, but it also means I will get longer run times overall! (I may still install a BOOST button which will allow full thrust just for fun!)

I must take the time to post my project, but also thank you for the inspiration.

No Doubt! Would love to see what you are working on! That is the best part of this forum, is seeing how each builder overcomes issues and how each persons ideal vision on an ROV is slightly different!

Thanks again for the comments! Looking forward to seeing your project!

Ryan
"KR2_Diving"

Hey Ryan,

Thanks for the reply

I've finally taken the time to post my ROV project 'The Mimee', and really found it helpful just to document progress, or lack thereof. Look forward to your feedback

Steve (Tal)

KR2_Diving wrote:At the moment I am thinking of an Arduino Mega in the Sub and a Uno at the surface. I think I am going to use RS485 coms to communicate between the two units... cheaper (and smaller) then the Ethernet shields!
"KR2_Diving"

Hey Ryan,

Are you still thinking of using RS485? I was planning on using an Uno on the surface, with Mega in the ROV, like yourself but as has been the case with everything, just discovered its not as simple...I had myself thinking it was as easy as hooking up tx to rx, and visa versa, and running some simple code etc. It seems that I could do this, and its called I2C, and really wouldn't be suitable for any reasonable depth (distance). If you have the time, could you talk me through RS485, or point me in the right direction?

Thanks in advance

Tal wrote: If you have the time, could you talk me through RS485, or point me in the right direction?

Thanks in advance

Hey Tal!
I am actually working through this this weekend. At the moment, I am playing with another library that Bill Porter wrote. (Same guy that wrote the code I am using for my PS2 Controller.)

I also have found some good tutorials on understanding the basics of serial communication. You can find there here:
http://www.jeremyblum.com/category/arduino-tutorials/

After I get my code squared away, I will be sure to post it!

Thanks heaps for the quick reply,

After realizing I2C wasn't going to do the job, I quickly ordered some MAX485 IC's. From what I understand, that's the only hardware required, along with the code but I'll be waiting a couple of weeks for those to arrive. As soon as they do, however, I'll be straight into it and hope to be able to contribute! Thanks for the link, too. I'm watching now I look forward to your next update!