My "MINIRAY" Rov.
Posted: Dec 2nd, 2011, 11:11 am
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.
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.
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.
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.