My "MINIRAY" Rov.

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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

My "MINIRAY" Rov.

Post by bigbadbob »

Hi Folks. here's a bit about my build, as an ex pilot/tech now working on AUV's i have access to parts and tools that most home builders don't get a sniff at. so i count myself lucky there.
My Mrs bought me a helmet mounted action camera as a present and it is supposedly rated to 10m. i didnt want to trust it and wreck it, so thought i'd build a waterproof housing for it, then it grew legs and i decided to add thrusters etc.
It has now become a fully fledged mini rov build.
As i've flown videorays before i wanted it to be similar to them.

Image

Description edited july 2017 to reflect current setup.

Hull-
Scrounging in the scrap bin at work provided my pressure hull, a length of ABS class E pipe 88mm (3.5") diameter and with 8mm thick wall. this will withstand very high pressures (16 bar internal and much more external).
Front cover is 3mm perspex dome.
Rear cover is a 5mm perspex plate which carries the umbilical connector and depth pressure sensor.
End covers are retained with aluminium plates and 4 off m6 threaded bar the full lenth of the hull.
My original method of screwing into the end of the pipe didn't work and just cracked the pipe.

Camera-
I was going to use my action camera, but I bought 4 broken cctv cameras off ebay for a mere £8 because i wanted the domes, but one of them turned out to work and is a fantastic camera. (samsung sid70p) it fits perfectly in my hull and is super low light (0.001lux) and pretty high definition. (600 lines colour, 700 lines B/W). automatically switches to B/W in low light.
I'm going to fit a leak sensor that kills the camera power in the event of a leak, this both protects the camera electronics and indicates a leak without the need for a comms uplink. I would like to add an osd or hud but it's not essential.
The domes proved to be useless. good buy though!!!

Thrusters-
3 off 8-16v pumps type L from "RC sub workshop"
Two for fwd/rev/yaw and one vertical.

Control-
I'm using a velleman 10 channel 2 wire remote control converted to 12v supplied from the controller end rather than the receiver end. As I am sending 12v down the tether anyway, this means i only need one comms line not two. I also prefer current loop control rather than anything that depends on voltage levels.
The receiver drives a bank of spdt relays in an H bridge for forward/reverse and up/down control.
The control box itself houses two 12v 12AH SLA's as well as the thruster switches and velleman transmitter. it has an rca video out for the monitor and sd card dvr recorder.
As thruster power is supplied over seperate umbilical cores from the electronics, I have a brushed ESC topside driven by a servo tester so i can control thruster speed, the set speed applies to all thrustersat once, not individually.


Tether-
I tried cat5 but, of course, even doubled up it wouldnt cope with three amps.
So i'm now running two 14awg wires for thruster power/gnd and two 18awg wires for electronics power/gnd.
Keeping them seperate stops interferance from the motors from distorting the video.
I also run a mini coax for composite video up, and a 20awg wire for comms down.
All tether wires are overbraided with expando pelyester sheathing and have a bouyant polypropylene strain string bundled with them.
The tether goes through a waterproof connector i found in the scap box at work, this means the hull penetration is guaranteed to be watertight to 2000m. it has six pins and will carry 5 amps per pin.
Tether is currently 100ft. i'll see if i need to go any deeper but doubt it.

Lights-
None!! from previous experiance of having lights close to rov cameras, in the waters round here you just get backscatter off the sediment if you use lights and can see more with the lights off as long as you stay above 50m, it gets a bit dark below that.
You need about 4 ft seperation to avoid the backscatter and my rov just aint that big.

Bouyancy/ballast-
Bouyancy is "kingspan" insulation shaped and coated with gellcoat. ballast is from a pair of strap on ankle weights the exercise freaks use and a selection of stainless nuts.

Sensors-
GY-26 digital compass.
Automotive pressure sensor for depth.
Optical leak sensor.
Infra-red receiver to trigger various settings such as compass calibration.
All sensors are fed to a modified "minimosd" on screen display board to show sensor readings on screen, this saves running an extra umbilical wire with sensor data.

Monitor-
7"tft monitor from china.

OK..I'd better stop now, this is becoming a saga. looking forward to your comments. ;)
p.s. appologies for the mix of metric and imperial measurements. i work with american hardware a lot but also metric so i use both.
Last edited by bigbadbob on Jul 29th, 2017, 4:19 pm, edited 3 times in total.
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: My "MINIRAY" Rov.

Post by bigbadbob »

Since my last post I have had good and bad news.
First- I got two more out of the four cameras working so i have spares in case i flood one.
second-I blew up my velleman reciever and now need a new PIC chip for it.
Have contacted both velleman and ESR to see if they will sell them seperately, fingers crossed.
but if anyone on here has one going spare that they would like to sell me please post here.
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: My "MINIRAY" Rov.

Post by bigbadbob »

Good and bad news today too-
bad news- i was at sea launching an AUV in a snowy whiteout, brass monkeys needing a bit of brazing done.
Good news- i got a reply from velleman to return my pic to them for inspection/replacement. for copyright reasons they want the old one back.
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: My "MINIRAY" Rov.

Post by bigbadbob »

Got a bit more done today, while waiting for my PIC to come back from Belgium i added an Amiga Joystick to my control box. Thanks for the idea Steve. I ws able to move the microswitches in the stick so they sit diagonally. this now plugs into my control box using a 9 pin D-type connector and is wired in parrellel to my switches so i can use either.
The fire buttons ae wired to work the vertical thruster.
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Mareike
Posts: 51
Joined: Dec 8th, 2011, 1:41 pm
Location: Thailand

Re: My "MINIRAY" Rov.

Post by Mareike »

Hi,
I want to go deeper and some 'real live' ROV guys told me to go with the light as close to daylight quality as possible, then you might get a better screen pic. The pipe is a great solution with plex.. you can't go wrong as well.. may be wee meet us at 100m (will be my first target without pulling water probes) and if I find somebody here who brings me out of the Siam Bay (max 80m overall) into the Andaman Sea I will go for the 200m marker..
btw just cut a straight ring of your pipe and use it as flange, that avoids breaking the plex.. my dad brought me some from England and well, that stuff doesn't excuse hard tightening :lol: so when he returns from his work, he has some more in his suitcase or short: I made this experience on 3 plex windows. :shock:
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: My "MINIRAY" Rov.

Post by bigbadbob »

Hi Mareike.
Good tip about the flange, cheers. i was thinking of maybe cutting a metal ring but the pipe would be easier.
Good luck with your project, 200m would be good. if you have an umbilical connector on your rov i'd reccomend diving to 50m, then coming back up and re-tightening your connector before going to 200. we used to do this regularly on the super scorpio. especially if we'd disturbed connectors since the previous dive and definately before going to 320m.
The pressure flexes the rubber seals and loosens them.
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: My "MINIRAY" Rov.

Post by bigbadbob »

Things are quiet at work so i fitted a vaccum/fill point to my hull and pulled a vaccum on it. sadly it leaks, so i back filled with nitrogen to +2 psi and sprayed all the suspect points with leak detect spray. it's leaking where my thruster wires enter the hull so i picked out the sealant and re-did it with "Belzona", a kind of liquid metal. once that's dry i'll re-test.
The holes in the hull are drilled the size of the wire and then counter drilled half way through to get plenty of sealant in, i pulled a vaccum before the sealant cured to draw it down into the hole.
I also carved a new bouyancy block from "Kingspan" wall insulation, i've sprayed this with laquer to seal it before giving it a layer of gelcoat. fingers crossed this will work. i'll keep yous posted.
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Mareike
Posts: 51
Joined: Dec 8th, 2011, 1:41 pm
Location: Thailand

Re: My "MINIRAY" Rov.

Post by Mareike »

I will connect all Tanks and Housings together with clear Hoses and this one:

http://www.conrad.com/MALE-HOSE-ADAPTER ... t%7D%7Bcmd

... and all electrics will go though the pipes..
so that only the tether is really going 'outside' and even that tether I will use one of these. and close the Hose by using a heat shrink, with glue inside at least 6' long. (at the end of the hose also a piece of solid pipe to avoid the water pressure will squeeze the pipe and make it leaking. Don't forget a sealing ring or o-ring when you screw it through the housings! I guess that will do it
and if not I might think again about the fact that I am a woman and start playing with babie dolls again :lol:
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: My "MINIRAY" Rov.

Post by bigbadbob »

Connecting all parts with pipe should work well Mareike.
Being female is no barrier to good engineering, Don't even think about going back to dolls, lol.
It's a shame more women don't want to be engineers, those that do provide a diffent angle of view from most men and the more angles you approach a problem from the better.
keep at it and keep us posted.
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: My "MINIRAY" Rov.

Post by bigbadbob »

Just a quick update.
I got my velleman chip back from them, all is now well on the control front.
I finished my bouyancy and trimmed my ballast.
I've been working on the code for my compass hud, still waiting for the hud chip but i've got the compass and microprocessor, i'm using the same u.p. as the arduino so i can use their software to program it. looking promising so far.
I got the magnets so i can experiment with magnetic couplings but being off work at the moment i aint got access to a lathe.

heres the stoy so far.
Image
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