Taking the plunge (!)

[KDM]

First project is underway. I've opted for:

Construction: PVC electrical trunking and plumbing parts
Propoulsion: 3x propeller converted 350GPH bilge pumps
Control: Wii nunchuk.
Processor: Microchip PIC or Arduino Mega
Max depth: Initially targeting 5m depth.

20121216 uROV1 01.JPG (354.82 KiB) Viewed 7140 times

You can see the shape of the chassis. The black tube at the top is one of two. They are watertight with acrylic sheets clamped to them. Inside, I plan on putting a USB camera in one and a 50W light in the other. For now they also form the most part of the buoyancy. One part converted motor sits in the foreground.

After a rough calculation, buoyancy is going to be a problem. I reckon my configuration weighs around 2.8kg and my buoyancy compartments displace only 1.6kg of water. I've assumed no buoyancy from the PVC chassis: I've read many posts confirming my suspicion that these tubes are virtually impossible to make watertight. I plan on filling them with expanding foam. Has this been tried?

Is there any evidence of folk having used a Wii nunchuk for this before? It has a neato I2C interface, which will hook into the Arduino or PIC without issue. 3-axis accelerometer, 2-axis joystick and 2 buttons. What else could you want?

[KR2_Diving]

Is there any evidence of folk having used a Wii nunchuk for this before? It has a neato I2C interface, which will hook into the Arduino or PIC without issue. 3-axis accelerometer, 2-axis joystick and 2 buttons. What else could you want?

Hey KDM,
I had a play with the Wii chuk a few months ago with an arduino uno. very slick interface indeed! i switched to a ps2 controller because I had some other plans for control, but i am still considering taking the board out of the chuk and mounting it in my rov, nice cheap sensor package!

i will have a look for my notes and post in the next day or two.

Ryan

[KDM]

Ah. Putting the nunchuk inside the ROV does give a nice cheap "right way up" sensor. I was thinking of the stick for fwd/back/yaw with the x-axis accelerometer for pitch with a button for stepped brightness control on the lights.

[KR2_Diving]

The idea of using the tilt to control movement is a pretty cool idea!

You might find these links helpful if you want more info:

Great adapter so you do not neet to modify the chuck at all!
https://www.sparkfun.com/products/9281

Paper that has a lot of basic data on it. There is a section near the end describing using the Chuck with an Arduino.
http://todbot.com/blog/wp-content/uploa ... class4.pdf

Ryan
"KR2_Diving"

[KDM]

I have some test data from my 350GPH Seaflo bilge pumps converted with 50mm two blade props.

20121217 Motor.JPG (323.69 KiB) Viewed 7105 times

I used a test rig as close as I could to that seen elsewhere.

20121217 Motor Test.JPG (204.28 KiB) Viewed 7105 times

The current appears to increase quite linearly with the Voltage, although the reverse current is typically about 100mA lower.
Assuming the relationship between voltage and thrust is linear, forward thrust (in g) seems to be around 8 times the Voltage and reverse thrust seems to be around 6 times the voltage (assuming all the required current is there).

Thrust for Power.JPG (41.12 KiB) Viewed 7105 times

It's difficult to be upset with figures like that.

Max measured current was 1150mA at 14V, but that was sucking down a lot of air in my little test tank. The pump was originally rated at 1800mA.

[KDM]

I decided I was going to be more adventurous and go deeper, but didn't want to run 10 Amp cables in the umbilical. Pretty sure this means I've got to submerse the battery, too. I'm thinking a couple of sealed lead acid home alarm batteries ought to suffice.

That means I need bucketloads more buyoancy. The buoyancy chambers I made are fibreglass filled with expanding foam. There are two of these. Each weights 450g and displaces 3.1L.

20131215_Bouyancy.jpg (122.67 KiB) Viewed 6445 times

[KDM]

50W 12V halogens. Bad call. P=IV, I=P/V = 50/12 = 4.1Amp, which is twice as much juice as the motors! I'm off to find LED lamps.

[Tal]

Hey KDM!

Good call on the Halogens! I found some cheap LED torches at a discount store for a couple of dollars each, that I've stripped down for use.

How does the buoyancy look now?

[KDM]

Two of the above canisters made in fibreglass. They each displace 3833g of water and their mass 700g each. That's a truckload of bouyancy.

I've decided to code the topside controller in Java on a PC. First project in Java. I got a quad H-bridge driver board https://www.sparkfun.com/products/11593 and it's happily driving my converted bilge pump motors from an Arduino.

Still going with sinking the batteries and using a USB umbilical for the first outing.

[a_shorething]

Two of the above canisters made in fibreglass. They each displace 3833g of water and their mass 700g each. That's a truckload of bouyancy.

I've decided to code the topside controller in Java on a PC. First project in Java. I got a quad H-bridge driver board https://www.sparkfun.com/products/11593 and it's happily driving my converted bilge pump motors from an Arduino.

Still going with sinking the batteries and using a USB umbilical for the first outing.

Good find on the controller board. I would test out all motors running simultaneously to see how much heat they generate and/or if it can handle it. One of the issues that concerns me about the combo boards like this is that they may not all be able to handle all circuits at the same time.

Keep us posted.