Experimental ROV Design using Blue Robotics Components

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SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

For those of you who are going to control your BlueESC Thrusters over the I2C bus, you will obviously have to program each Thruster with its own unique I2C address.

The instructions for doing so are available from the Blue Robotics Documentation website. Changing the BlueESC I2C address is done by reprogramming each BlueESC with the correct idX.hex firmware. According to Rusty, the starting I2C hex address 0x29 corresponds to firmware id0.hex while I2C hex address 0x2A corresponds to firmware id1.hex and so on.

Presently I have programmed my Seeeduino Duemilanove with the ArduinoUSBLinker and have loaded and run the KKMulticopterTool on my laptop. So I will be ready tomorrow to begin reprogramming the I2C addresses of my six T100 BlueESC Thrusters.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

Good news!

Today I programmed each Blue ESC with its own unique I2C address which for the six Thruster ESCs were hex addresses 0x29 through 0x2E which correspond to programming firmware id0.hex through id5.hex.

After successfully programming each Blue ESC's unique I2C address, I proceeded to communicate with each Blue ESC using the Arduino I2C ESC program which provides the ESC number, RPMs, Voltage, Current, and Temperature.

So far so good. Now it is time to connect the Thruster ESC power cables to their respective Battery Junction Board connections and the Thruster ESC Control Signal cables to their respective Signal Junction Board connections so I can begin to button up the Battery and Navigation Controller WTCs and run some vacuum tests to insure the watertight integrity of each WTC.

More to come.

Regards,

SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

I would like to point out at this time that if there is a problem communicating with the BlueESCs over the I2C bus a simple reduction in the clock rate of the I2C bus should cure the problem.

In my case, the signal control cables of the two BlueESC Thrusters located at the front of the ROV Chassis were almost 1 meter long and as a result of the long signal control cables there were issues trying to communicate with these two BlueESC Thrusters over the I2C signal bus.

Rusty, from Blue Robotics, suggested that I slow down the I2C bus speed to around 12.5khz by inserting the following code right after the Wire.begin(); command that starts the I2C function:

TWBR = 158;
TWSR |= bit (TWPS0);

The change in the clock rate from 100kHz to 12.5kHz does not seem to appreciably affect the response of the BlueESC to speed or data requests and will be worthwhile for any BlueESC Thruster user who does not want to use PWM and is having trouble with the I2C bus.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,
Rusty at Blue Robotics suggested that I also try the I2C bus clock frequency at 25kHz and 50kHz.

So I picked the BlueESC that I had had the problem with a 100kHz and tried communicating with the ESC at both 25kHz and then 50kHz. The ESC responded to speed commands and returned telemetry flawlessly at both frequencies. I then tried 100kHz again and as before found the ESC to be unresponsive after a few moments and the motor running out of control.

Therefore it looks like that 50kHz is the maximum I2C bus clock speed that my setup will reliably run at without communication issues. I did notice somewhat faster response to speed change commands when running at 50kHz rather than 12.5kHz.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

This weekend I have started testing the watertight integrity of both the Battery Compartment WTC and the Navigation Controller WTC.

I have tested each WTC individually, however I have not tested for the watertight integrity of both WTCs with the battery power supply cable connected between the Battery Compartment WTC and the Navigation Controller WTC. I chose the Battery Compartment WTC to connect the new Blue Robotics vacuum plug adapter to be able to pull a vacuum on both WTCs. You might ask, how are you vacuum testing both WTCs if you are only connecting the vacuum line to the Battery Compartment WTC? The answer is quite simple: The battery power supply cable leaks and allows air in the Navigation Controller WTC to move from that WTC to the Battery Compartment WTC. So it takes quite a while to pump down both WTCs as the battery power supply cable leaks at a very low rate from the Navigation Controller WTC to the Battery Compartment WTC.

I initially spent about 3 hours yesterday trying to pumping both WTCs down to 560 mm Hg. I would pump the Battery Compartment WTC down to 560 mm Hg and then come back in 15 minutes and pump it down again to 560 mm Hg. Eventually the Battery Compartment WTC began to approach 560 mm Hg with each pump down.

As I write this post this morning both WTCs appear to be approaching the point where the vacuum will stay at 560 mm Hg in the Battery Compartment WTC for at least an hour indicating that both WTCs are at 560 mm Hg of vacuum.

After my last pump down, which I performed at around 12:30 pm EST, I waited for half an hour and then opened the WTC vacuum cutoff valve and found that the vacuum gauge did not move off of 560 mm Hg. I then pumped down the WTCs for around five more minutes before closing the vacuum cutoff valve. If both WTCs are at 560 mm Hg after another hour, then I can be sure, based on previous pump downs of the individual WTCs, that both WTCs are watertight.

More to come.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

Good news! An hour after the final pump down of both WTCs to 560 mm Hg I found that the WTCs' vacuum was still holding at 560 mm Hg. So I ran the vacuum pump for about three more minutes and then closed off the vacuum cutoff valve.

I will now wait for around 24 hours before checking the WTC vacuum level again. If all goes as before when I tested each WTC singly I should see a slight vacuum loss of around 20 mm Hg which I have attributed to the vacuum cutoff valve not being perfectly airtight.

At this point I would like to say that I am glad that I have my 12 vdc electric diaphragm vacuum pump instead of the hand powered vacuum pump that I started my testing with. I know that Rusty is showing the hand pump in his vacuum testing video, but if you want to test the water tightness of the cable interconnections between two WTCs you are going to get a lot of blisters on you pump hand as that is a lot of pumping to do to reach 560 mm Hg of vacuum.

More to come.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

After waiting approximately 20 hours I checked the vacuum in the two WTCs and found that it had only dropped 10 mm Hg to 550 mm Hg which to me is indicative of a good watertight WTC based on the previous testing of the individual WTCs. The slight loss of vacuum can be attributed to the vacuum line cutoff valve which I believe is not completely leak proof.

I now have to wait for the Tether and the Navigation Controller to become available so that I can continue with completing the ROV. In the meantime I plan to fit the Battery and Navigation Controller Trays in their respective WTCs and remove the blue tape from the ROV Chassis.

More to come.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

While waiting for the Tether and the Navigation Controller to show up I decided to setup the ROV onboard camera. Many ROV builders put the camera in their WTCs so that they can mount them on gimbals or avoid having to purchase/build an additional watertight enclosure for the camera. I chose to identify and choose a waterproof camera case that could provide access to the standard definition output of a GoPro camera which could be sent back up a twisted pair in the ROV Tether. The waterproof case would allow me to mount the GoPro anywhere on the ROV chassis and not be limited to just viewing out the front of the WTC.

I managed to score a GoPro Hero 3+ camera from Costco during a sale in late November of this year. As you might know, the GoPro camera case is waterproof down to ~131 ft, however you must wait until the ROV has returned to the launch point to retrieve and view the camera high definition (HD) output.

Fortunately, there is a way around this limitation and that is to use an Eye of Mine GroPro 3/3+/4 waterproof camera case that has a standard definition (SD) video cable output at the back of the waterproof case. Yes, a high definition (HD) output would be nice, but not for this inexpensive camera case. With this camera case setup I can view what the ROV can see in real time SD and then review the same scenes in HD once the ROV has returned to the launch point and the camera has been detached from the ROV. The Eye of Mine GoPro camera case came with a waterproof 6 foot composite video cable that I will modify as necessary to get the cable potted to a 6 mm cable penetrator on the front End Plate of the Navigation Controller.

Below are some pictures comparing the Eye of Mine GoPro waterproof case to the standard GoPro Hero 3+ case:

Image
Front view of Eye of Mine GoPro Camera Case

Image
Top view of Eye Of Mine GoPro Camera Case

Image
Rear view of Eye of Mine GoPro Camera Case

I have ordered a Blue Robotics 4" Series WTC Flange and a 4" Series Acrylic End Cap with 5 Holes to replace the blank 4" Series Acrylic End Cap in the front of the Navigation Controller WTC. I will block off all of the End Cap cable penetrator holes with blank cable penetrator except for one hole I will use to route the composite video cable from the Eye of Mine GoPro camera case into the interior of the Navigation Controller through a 6 mm cable penetrator.

More to come.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

I have established two camera mounting points on the ROV Chassis. One mounting point is at the center of the top of the top front chassis cross brace while the other mounting point is at the center of the top of the lower front chassis cross brace.

The picture below shows the location of the Eye of Mine GoPro Hero 3+ camera housing mounted on the top of the lower front chassis cross brace:
Image
Eye of Mine GroPro Camera Housing mounted on ROV Chassis lower front cross brace

The camera housing mounts right in front of the Battery Compartment WTC front End Cap and would normally interfere with the removal of End Cap to service the batteries. However, since the camera housing can be detached from the chassis mount, it can be swung out of the way to allow easy access to the Battery Compartment WTC front End Cap.

Regards,
SSN626B/TCIII
SSN626B
Posts: 194
Joined: Nov 16th, 2013, 2:11 pm
Location: Ft. Lauderdale FL

Re: Experimental ROV Design using Blue Robotics Components

Post by SSN626B »

Hi All,

Since the WTCs are round you might be wondering how I plan to keep the Battery Compartment battery tray and the Navigation Compartment electronics tray from rolling from side to side inside their respective WTCs when the ROV Chassis rolls from side to side.

After much thought, I decided to cut the trays slightly shorter than the distance inside the WTCs between the inside ends of the O ring front and rear flanges so I could add a rubber snubber to each end of each tray. The trays are now sandwiched between the inside ends of the O ring flanges with the rubber snubbers compressing against the end of the O ring flanges. The friction provided by the rubber snubbers holds each tray in place between the inside ends of the O ring flanges even if the ROV Chassis rolls from side to side.

The pictures below will give an idea of how the snubbers are positioned between the ends of the trays and the inside ends of the O ring flanges:

Image
Navigation Controller Tray sandwiched between the front and rea O Ring Flanges

Image
View of the Front O Ring Flange and the rubber snubber on the front of the Navigation Controller Tray

Image
View of the Rear O Ring Flange and the rubber snubber on the rear of the Navigation Controller Tray

The rubber snubbers are fabricated from 1/8" thick rubber sheeting, attached to the front and rear of each tray with medium CA, and then sanded on their faces to provide a tight fit between the inside end of each of the O Ring Flanges when the Flanges are compressed into each end of the WTC.

More to come.

Regards,
SSN626B/TCIII
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