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Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
I will be documenting here my school Senior Project: two Remote Operated Vehicles (ROVs): one is a small mini-sub based off of a combination of many homemade designs and a lot of my own planning. The second vehicle is a Remote Control Go-Kart (the vehicle is already built, standard two seat go-kart, I am just remote controlling it). I will be discussing the Mini-Sub ROV here.
UPDATE (5/4/2010):
My project was due May 3, 2010, and I got most of it working save that a valve on the BCD blew while doing a full scale test : - / But, my sponsor was very impressed overall and thought I did a very good job with my design and revising things as they progressed. I still am awaiting the official grade pending the review of my Official work log, found Here on my Website
I will also update this work log to include new information.
This project will continue for a long time as I upgrade it, rebuild finicky sections, and put it to use!
-Jimmy
The ROV is detailed as follows:
Controls and Tethering: Controlling the Mini-sub will be done over Fiber Optic Cable, as it allows very long tether lengths, has a thin wire easily threaded through Vinyl tubing, and is non-electrical so if there is a short, or the tether snaps, there is no electricity going through the water or back up to the controls. The Sub end of the tether will go to a Fiber Media Converter, which turns the fiber connection into a more easily used Ethernet connector. This is then run through a switch, allowing both the Ethernet Enabled Arduino and the Ethernet based Camera to share the line. The Ethernet Shield on the Arduino can be setup as either a server, or client, but most likely a server that is access by the controller. The control end of the tether goes to my laptop, which is in a protective case on the surface, which is connected to the Control Panel. The control panel will be water resistant, so if it falls in it should be fine as long as it is fished out. It will be built into a Pelican Case to help ruggedize it, and I have already started on the panel mounting. The Control Panel will allow control of Depth, forward/revese, side-to-side, and rotation. It also will have control over the lights on the ROV, and possibly a few other "add-ons" TBD. The control panel will have a "test mode" selection that will allow the operator to check whether or not the Software is properly sending signals to the ROV by not sending the relay enable functions, so the arduino will display on the LCD that it is working, but the main relay will be off preventing power from going to the Bilge Pumps. There will be software running on the laptop that will run the controls from the physical panel to the Ethernet port out to the ROV. The panel will also have an important safety feature: a killswitch that will shut down the fiber link (without which the Arduino will assume server loss); and an emergency surface control that will open the CO2 Regulator to full buoyancy and surface the unit.
Propulsion: The propulsion method will be to use Bilge Pumps (most likely a four or so Rule 500 GPH pumps and two 1000 GPH pumps). These will be controlled by opto-isolated relays, fed by a battery. The pumps will suck in ambient water and simply shoot it out of their respective nozzles in a pseudo-jet propulsion method. The isolators are needed to help prevent shorts from frying the electronics, and in water the chance of a short goes UP!
Sealed Compartments:
The main power for the ROV will be SLA Batteries. They will be in an inner, sealed compartment. So if the water seals fail on the main compartment, the batteries have an extra line of defense. They will have fuses internal to their compartment so that if there is a short or water gets into the main compartment, the fuses blow and not the batteries.
I likely will have a second, separate inner compartment for the more sensitive electrical components as well, such as the ethernet devices and the Arduino setup.
Camera and lights: the camera will be housed in a separate part of the ROV from the main electronics, connected by an ethernet cord run through the PVC frame of the ROV. It will have a Lexan viewing window. The lights will be connected directly to the main compartment by small pipe struts that move forward from the compartment to above the camera housing.
Main Structure:
The ROV's frame will be a Rectangular Prism design, and about the size of a small desk. It will be open frame, all PVC (both slip and threaded type, all sealed). There will be some plastic mesh to mount things like the Bilge Pumps (similar to Rollette's design).
Buoyancy Control:
The Buoyancy of the unit will be controlled remotely from the main panel, and adjusted on the ROV by using a Paintball CO2 Canister combined with a small regulator and electric valve (possibly a sprinkler valve, they work well with gas pressure in many models). The ballast tanks will be of a geometric design I have made (and will post soon) that allows the displacement of water by gas, or vice versa, without needing a release valve, but using natural gas/water displacement. For example, to flood the ballast tanks I would only need to turn on the bilge pump to pump water in, and do not have to open a gas valve to release. And to empty the tanks I only need to open the gas valve to let gas in, no need to activate a pump to take the water out of the tanks. There will be either two or four tanks, all controlled by the same CO2 Regulator and Bilge Pump, all equally adjusted in real time.
I will update information and pictures as they come along, so far I have gotten the Arduino Ethernet Shield to respond pretty fast
(3/28/2010): I have made more specifics/started construction on the following:
*** An Army Surplus Ammunition Case will provide the main housing for the electronics, as it is by nature waterproof, large enough, cheap to obtain, and easy to modify. I have purchased a case already for about $20 that is about 3 feet long, one foot wide, and several inches tall.
*** started making schematic for Surface Control Interface, basic schematic attached and code will be uploaded soon
(This Schematic had problems in testing due to the floating abilities of the I/O pins, and the fact that power too easily drained from other areas -- I have replaced it with an Opto-Isolator interfaced matrix which is stunningly responsive and reliable - the new schematic will be up soon as I make it, as when I was modifying the circuit I just had it in my head and never really wrote it down)
*** connections to Bilge Pumps will be made watertight by use of a combination of PVC Compression Fittings, and Sealant. The wires will enter a small piece or PVC and be sealed to made one end watertight, then that piece of smooth PVC will have the other end sealed using a compression fitting that is sealed to the Ammunition Case permanently. This will allow removal of the wiring should it need to be maintained, at worst I will have to rip the sealed wires out of the strait piece of PVC and reseal that part, but that is very easy. A similar type of connection will be used for the Fiber Optic Link to the control interface
here is a pic of the Compression Fitting Opened to show the seal, which is compressed by threaded PVC and below that is a pic of the Gasket Kit I picked up at the hardware store
*** The connections to the Camera and lights, which have to be mounted at the front (non-opening) end of the Ammo Case will be sealed with a Rubber Boot designed to slip over smooth surface pipe and be tightened with hose clamps. this is used to make mounting on this end of the Ammo Case easier, since it is too long to easily make threaded connections. A smooth flange will exit the case, with the flange base on the inside with a gasket affixed before insertion, and will be sealed with sealant and then affixed with the boot. The camera and LED lighting will be in their own PVC configuration, and the boot will be an added bonus as a shock absorber due to the fact that if there is a collision, it will occur most likely on this end of the ROV.
(I have decided to wait before drilling the boot hole, as I may just use another compression fitting and rub a cable to the back of the Ammo Case, as the internal wiring might be a bit easier)
***The control panel itself is under construction, and once the interface circuit is completed I will begin testing the code used to control the Arduino. For testing purposes, an LCD will be attached to the Arduino so that I can see what command is being registered, before going through the trouble of configuring the bilge pump relays.
----4/2/10 Build Update---------------
I obtained two 500GPH Rule Bilge Pumps for the rotation propulsion, and I am going to call Attwood about their blower's waterproof rating as they have no answered my emails yet
I Built the PVC Frame today, it will be painted Bright Orange or Green depending on which once proves more visible underwater. The Frame measures 45 x 20 x 20.5 Inches (114.3 x 50.8 x 52.1 Centimeters) with an interior Component space (ammo case, bilge pumps, ballast tanks, etc) measuring 40 x 18 x 10 Inches (101.6 x 45.7 x 25.4 Centimeters)
I decided to use an old (but perfectly good) OtterBox as the enclosures for the Sealed Inner Compartments, there will be two of them so I'll have to pick up another but unlike pelican cases they are very cheap due to their simplicity, and a local shop has a few lying around for about $10
To keep the air inside each of the compartments dry (and by doing so help combat condensation due to temperature differences causes by the water) I will be using a few small sacks of Dririte from my Chemical Supplier, which can be regenerated by heating. I do not expect condensation to be too much of an issue, but I will be cautious around the more sensitive or disaster-prone areas such as the Batteries, Fiber-Optic Media Converter, and the main CPU
I also decided on my method of gas control for the Ballast Tanks: the tank will be inverted U design, as the ROV never tilts significantly unless something is wrong. The CO2 Tank will feed into a Paintball Gun, all of which now-a-days use an Electronic Control System and therefore will interface with my circuitry without buying an expensive electronic valve. This will allow co2 into the top of the tank, and since the tank top is closed and the bottom open the water will naturally flow out. To let water in and gas out, a Magnetic System will open control a manual valve that lets the gas out. I plan to use a magnetic system for a number of reasons: it is very easily waterproofed and the electromagnet has no moving parts; unlike the paintball gun, a standard valve with a spring will be more durable in the upper section of the ballast tanks and will survive if water gets in, and a paintball gun system might not work the with pressures involved in the ballast system which are not similar to a paintball tank
A bonus to this ballast system is that I can "fire" the paintball gun at a specific rate, or manually for very fine ballast control.
*****Main Board Assembly has Begun!
one end of the main board, has the Power Supply (Batteries and a regulator inside an Invisible OtterBox hehe), and the Relays that drive the Bilge Pumps, the Paintball Gun, and the Ballast Drain (in order from top left to right: Forward, Reverse, Left, Right, POWER, Ballast Float, Ballast Sink)
The other half of the Main Board which has the CPU (Arduino, Fiber Optic Media Converter, etc) in the Visible OtterBox, the Paintball CO2 Tank, and the Paintball Gun which will have the ball intake plugged, and the Barrel connector will be used for the Ballast Hose
A portion of the CPU Guts:
Paintball Gun Electronics, I will simply tap into the Trigger Microswitch to control the gun, for now the power on will be done by hand when launching the sub (really a good idea when a gas handling system is involved):
I did a bunch of major assembly work over the past week:
I mounted a 1/8 Inch sheet of Polycarbonate (known as Lexan to many) to the PVC frame using lots of Zip-Ties (these prevent the sheet from moving, and the PVC provides structural support). This is the component mounting bed. I mounted the two rotational bilge pumps, test mounted (but not quite affixed) the ammunition case, and mounted the Forward Propulsion Bilge Pump, as well as painted the unit orange (will likely have to repaint, as no primer was used and I ran out of paint but that doesn't matter right now):
here is a frontal pic:
Here is a side pic:
Here is one of the mounted 500GPH Bilge Pumps (used for rotation):
Here is the package of an unopened Cooper Wiring Devices Waterproof Connector - I tested this at five feet overnight and had pretty much no water seeping in (there was a drop or two, but I think that was from me opening/closing it while the outer cases and my hands were wet). These will connect the Bilge Pumps to the Control Circuitry on the inside of the ammo case:
Here are the two cooper connectors mounted (I decided to NOT use a connector for the Ballast Drain, as I can work out the mechanics of the magnetic valve to have the electromagnet on the inside of the ammo case):
I also tested the forward Propulsion and the 1100GPH Bilge Pump did it's job to get the ROV moving at a decent speed. Not the fastest thing in the world, but it moves at a respectable rate considering a water pump the size of my fist is the only forward propulsion.
As of the writing of this update, I ammo case with mounted electrical connections are sitting just below the surface of my pool until the hour is up, then assuming no leaks they will be placed deeper, and so on up to about ten feet if time permits. Then if all goes well, I will finish the electronics and test them in the pool. Then I will do a deeper seal test at a local pool. then I will construct the Ballast System, which will be the trickiest part of the build.
Waterproof Seal Test Results: just below surface for one hour, no water! about 3 feet deep, some water but this is likely due to an improvised testing condition: I had to use zip ties to hold the ammo case onto the frame for the moment, and I noticed that two of the ties inhibited the latch from closing all of the way, and the water was minimal after two hours, so I am assuming the seal is good for now given that those ties will be removed.
However, I may have damaged one of the electrical connectors. When pulling the unit up to the pool deck after the first test, the case slid and pulled severely at one of the connectors at an angle perpendicular to the connection direction. I think the rubber molding may have been stretched a little, but I will have to test separately for this.
Minor Update 4/18/10-------------------------------------------
-------------------------------------
I installed a few minor components and laid out the new Bilge pump power switch circuit, only needs to be soldered. The new bilge pump drive is based around several Optoisolators which make things very easy, I may not use normal transistors every again . I installed the tubular key switch on the power supply box, which allows for three power modes: Off, CPU only, and CPU/bilge/ballast. I also installed a fuse for the battery (and about friggin time I did!). I also mounted an LM317 Regulator that will provide the necessary 5 Volts for the Fiber Media Converter, as well as any other accessories I might need. It is mounted underneath the lid of the battery compartment, just above the actual battery. The last thing I mounted today was the PVC Compression Fitting that I will use to run the Fiber Optic line, along with any other cables I need to allow a non-electrical feed through for.
I need to find a large amount of shot to place inside the PVC frame as the primary static ballast - the PVC and ammo case needed almost 100 POUNDS to sink the bloody thing!!! - with the shot weighing down the unit and removing air compartments inside the PVC frame, I should be able to drop the amount of other weight needed dramatically. - but let there be no doubt, this will be one heavy Son of a B***h!
I started the Variable ballast System gas handling construction by installing the gas check valve (one way valve) onto the end of a sawed-off paintball gun barrel to prevent the gas from flowing out of the gun and from water coming in... The epoxy on it is hardening right now, but once it is cured I will start some gas tests before installing the ballast tanks, which will end up being a lot smaller than I originally thought.
MAJOR problem encountered today that nearly killed $140 worth of electronics! I had just finished soldering the Bilge Pump drive board (only needed to add a resistor today to lower the current to the optoisolators) and guess what happens? first, all the power stops, turns out to be a blown 4 AMP fuse. I check checking around with my ohmmeter to see what's shorted, and this time I started checking other components on the board that should have been fine (no where near other components, etc)...
as it turns out, the protoboard I have has VERY small and VERY difficult to see traces along the bottom of the board, that are even harder to see because the laquer over them obscures the already small size. the ENTIRE board is joined with them! - I didn't have time to get a new board, so I take an x-acto and a razor blade to the bottom of the board, and I got no conductivity readings yay! - well, not quite turns out, some remained and it shorted the 12V SLA Battery passed the Optoisolators strait to the Arduino ground and fried the trace! - no the main trace on the arduino appears to be safe and that all of the damage was to the trace on the "Screwshield" I am using. After a few tense moments repowering the arduino (minus faulty circuit), a moment of relief came to see that the arduino and Ethernet shield still power up, but this raises concerns as to whether I blew out any of the pins! - I'll have to scrape some parts together to find out, and if I did (and especially if I screwed the Ethernet Shield) I may not finish this thing in time for my school deadline because I have to order things like arduino etc, but I may be able to rush the delivery (at a cost of course).
At least I was able to get a Scuba BCD (Buoyancy Control Device) from a local shop today for $25, and I can at least know that my Buoyancy System is ready to install should the electronics be safe
UPDATE: I rebuilt the circuit on a breadboard to test out the arduino and it appears I didn't fry any of the Arduino, just the traces on the board - I will have to remake a board for the circuit but with my time frame I may just leave the breadboard in for testing.
UPDATE: 4/22/2010---------------------
My latest water seals have failed, both Silicone and Gorilla Glue, I need to be able to work from the inside to see where the leak is exactly and I can't do that with my Ammunition Case, which is entirely end worked
For this reason, I am resolving to use one of my Pelican Cases (the 1600) which is currently in the water at depth to see if the O-Ring is still good (which it should be the case is not even half a year old)... if it holds, I will replace the ammunition case with it. I have the time to do this as I have dropped the Go-Kart from the school grading requirement as my instructor agrees that too many setbacks have left too little time for it. If the Pelican Case holds, I can make precision holds in the Plastic of the case which will allow for more reliable, and easier to make, seals than the Steel hull of the ammo case which is hard to drill and them use tin snips to make a large enough hole.
I expect that I could drill all holes, and get the seals ready to apply tonight if the test goes well, and the Electronics board will fit in the case as-is now that the Paintball Gun Section has been cut off thanks to the acquiring of a Scuba BCD unit. Then I will also, as a precaution, place the bilge drives in a psuedo-inner compartment, even though they are fuse protected if there is a short but I don't want to take any chances in case the seals won't hold up... I also need to buy a lot more Silicone, as I have to reapply my seals.
I have uploaded some pictures, and I have decided for the main seals on the electrical connectors to rely on RTV-8 Silicone, which on the original seals which used this particular type I had little issue with as long as I strengthened it.
I changed from the Ammunition Case to a Double Pelican Case (a 1520 houses the electronics, and the 1520 is inside of a 1600 giving a double hull design for every electronic component except the CPU and Battery which have individual Third Hulls - I'd love to see water reach these things lol)
The Pelican 1520 Case inside the 1600 Case, each has an O-Ring Seal and a Pressure Purge Valve.
A view of a Cooper Waterproof Electrical Connector, in my submersion tests these things held up pretty well (this one is unsealed when photo was taken and is meant for the electromagnets, hence the lower gauge wire than the others)
A view of a Cooper Waterproof Electrical Connector, in my submersion tests these things held up pretty well (this one is unsealed when photo was taken and is meant for the Bilge Pumps which need a thicker gauge wire for the higher current, I simply used a cut up power cord for these)
The Pelican 1520 Case closed up inside the 1600 Case
A Closeup of the Outside portion of the waterproof connectors, the rubber molding makes a decent seal on it's own but it is being given a generous amount of sealant as well.
A frontal view showing the connectors for the rotation bilge pumps (turn left/right) and the electromagnets which actuate the Scuba BCD
A Top view of the outside Case (minus the Fiber Optic Feed Through)
Scuba BCD (back side) which stands for Buoyancy Control Device
Frontal View of the BCD
Type SC Fiber Optic Terminations
80 feet of now sheathed Fiber Optic Cable surrounded by Vinyl Tubing (due to its flexibility)
A closeup of a section of tubing and the fiber cable inside of it.
A PCV end cap used in the PVC Compression Fitting for the Fiber Optic Feed Through, not in photo is the addition of "Coax Seal" Tape.
A view of the massive amount of Silicone used to support the cable and seal the feed through
The Compressed RTV-8 Silicone, it is like a Whipped Cream can, you bend the nozzle and it is propelled out - VERY easy to work with!
The Seal on the top part of the Fiber Optic Feed Through to the 1600 Case
The whole top of the Fiber Optic Feed Through in the 1600 Case
The Bottom Portion of the Fiber Optic Feed Through, sealed with RTV
The Ethernet switch which will allow the CPU and Two Video Feeds to share the Fiber Optic Tether, very compact and operates at 9V
A Sealed Cooper Waterproof Connector
A Heat Shrink like Coating Compound, makes a nice flexible seal for individual wires
Acrylic Coating Liquid, used to coat and seal entire boards and used to seal the 1520 Case Electrical Feed through
The Electrical Feed Through of the 1520 Case, and already sealed using the Acrylic Sealant
I performed a few underwater tests, and it works pretty well albeit two of the pumps are running very poorly, possibly due to accidentally leaving the pump test program running while answering a phone call - the call lasted about 20 minutes, and the pumps were being run dry!) - besides the two pumps that run poorly, the ability to Remote Operate the mini-sub works, the tether is buoyant thanks to some foam pipe sheath from the local hardware store, and all that is left is the buoyancy control for the basic working unit required for my grade. Well, the buoyancy control is becoming a problem - I may have found a solution to the proper actuation of the valves, but I need to go to the local scuba shop and test with some tanks before I rent them for a full underwater test. I have mounted one control valve for the BCD unit, and the other will be mounted once I determine whether or not this method works which is to use the solenoid from a Sprinkler Valve.
I will post more information as it comes - I would post a video of the thing moving in the water, but that would be pointless because it moves very slow due to the damage to two of the pumps, one of which is the 1100 GPH forward drive!
EDIT: I tested the BCD control valve, and it works but it is a little leaky, mainly because the pressure inside the BCD can start to open the spring, but this should not be a serious issue underwater as the water pressure will help things out, but on the surface it could cause a problem - but, for proof of concept purpose I will eave it because to find a stronger spring of the right size, then crack it open, replace it, then seal and test takes too much time and I might not get the right strength of spring. The valve assembly for the air intake is currently having the marine epoxy set, then I will touch up the seal and head back to the scuba shop - this valve will have a good chance at leaking slightly, but for the most part I want the unit to be slightly positive because then if there is a failure it will naturally surface, and actuating the air dump every few minutes is no big deal - but I may still need to try to adjust the regulator to drop the pressure going to the bcd a little
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
custom ordered props would take time, and then I would have to design them for the purpose but with bilge pumps, I get a ready-to-go system and if I choose to upgrade to props, I just use the motors from the bilge pumps and attach the props to them
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
Suggestion: instead of spending money at united nuclear on essentially expensive anhydrous CaSO4, why not go down to your local mega-home-renovation/building-mart and grab some sacks of anhydrous CaCl2? They are used commonly enough to dry areas when painting. The advantage is that its cheap, and you can always heat the salt in an oven to regenerate it. It has a fairly low capacity, but since you will be in and out fairly often, it could be standard procedure to swap out packets of the stuff.
Consider also attaching the batteries last so you can play with the balance and CoG.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
aonomus wrote ...
Suggestion: instead of spending money at united nuclear on essentially expensive anhydrous CaSO4, why not go down to your local mega-home-renovation/building-mart and grab some sacks of anhydrous CaCl2? They are used commonly enough to dry areas when painting. The advantage is that its cheap, and you can always heat the salt in an oven to regenerate it. It has a fairly low capacity, but since you will be in and out fairly often, it could be standard procedure to swap out packets of the stuff.
Consider also attaching the batteries last so you can play with the balance and CoG.
Just my $0.02, adjusted for inflation.
Thanks for the suggestion! - I already had the United Nuclear stuff, and the only reason I buy from them is because everything of theirs is ACS grade and comes in neat looking bottles (I collect chemicals for fun but am willing to use them and get the purity b/c I never know if I'll need it) - but the stuff from the hardware store might work better because I can get a lot of it, but also the compartments that the dehydrator will go into are very small
also, will that hardware store stuff act as an Indicator? - the stuff I have turns Pink when it is saturated.
as for the batteries, I plan to actually replace those with weights as I adjust things, but they will be in that spot nonetheless but I will have counterweights if need be, as my ballasting may be overkill naturally due to the PVC Frame (which I might fill with sand at this point as I have plenty of it) - due to the nature of the Exterior/Interior connection points, the batteries have to sit on the main central line and that point is almost on the center but just a little forward, the bilge pumps going in the rear of the unit should compensate for this
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040
GhostNull wrote ...
Why not RC??? No need for wires every where and no risk of tangle or getting snared on something
And you should paint it orange seeing as water can be green(ish) (or at water is greenish around here 0.o)
I figured Orange would be better,
but while I am licensed as an Amateur Radio Operator which has provisions for Radio Control, I do not want to construct a Transmitter which transmits through an Electrically Conductive Medium, especially since there can be Divers present around the ROV (should be WILL be, not can be, as I will be diving with a friend while testing the ROV) Also, radio signals on the frequencies allotted to US Amateurs may not fare well with submerged water environments at the depths required, and the transmission speeds - I will in fact have live video streamed up to the surface
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
The blue-pink indicator is CoCl2, the problem is that its not benign (actually toxic and carcinogenic); I wouldn't be happy if I released some into the environment by a leaky ROV pod. The hardware store stuff should be plain old CaCl2 desiccant, just ask for some desiccant and they should have it.
In regards to the battery/weight issue, its up to you ultimately what 'system' you want to design and what works for you. If you have money to spend I would recommend using 'Bulgin buccaneer' connectors; they are quite spendy, but other home made ROVs have had success with these.
I have considered building an ROV before but never had the inclination to nor the cash, hopefully I can give at least one idea that helps :)
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