I started off with a Madlabs ROV just to see how the thrusters and control reacted in the water and as a start point for my learning. Its a great start point and recommend it to anyone starting out. I figured that with the parts i already had to hand i could adapt it into a more serious ROV and test some electronics and tether ideas before spending countless hours on a bigger project.
-My Micro ROV is effectively the Madlabs design with a few 3D printed parts to make the frame more robust/place the thrusters further back.
-Then i have used a GoPro camera housing as my water tight enclosure (housing camera, three 10A brushed ESC's and a PPM to PWM converter).
-I found some foam that is the same as used in swimming floats (was actually a model plane stand i wasn't using) to use as buoyancy and some threaded rod/washers/nuts to use as adjustable ballast.
-Power comes from a 2cell LiPo that in on-board but exposed to the water (ive had no problems with RC cars in water) and control is from an RC transmitter but using the PPM signal over the tether.
-The tether itself is way overkill for this project but if works will end up on a bigger ROV. Its 1/4" braided polly rope with two twisted pairs taken from cat5 cable (making the tether was a days work in itself! But it turns out it was well worth it. Control goes via PPM down one UTP and SD video come up the other UTP. I left a length of rope without wires to attach to something substantial then the wires break out and go to the screen. All 100ft fit onto an old spool from 1kg of printer filament with the extra wires tucked on the inside.
-On the surface im using my old FPV ground station, its just a 7" monitor on a tripod with an SD DVR to capture the action.
-The controller is set with a delta mix on the two rear thrusters so i get forward/reverse and turning on the right stick then depth is controlled with the throttle stick, meaning i can leave a little thrust on to hold the depth. Feels really natural. Ive also adjusted to endpoints so the ESC's arent pushing too many amps into the little toy motors.
-Ive also changed the props to counter rotating to improve stability, all ive done for now is chopped down some quadcopter props i had hanging around. The pitch is low at 4.5 but they give more even forward/reverse thrust than the supplied toy props.
-Oh and there is a 1W LED bonded to the outside of the GoPro housing next to the lens.
-All wires pass through a hole in the housing and the epoxied.
So did it work? Well yes and no.
The good:
-Signal worked both ways over the 100ft of UTP fine without amplification.
-Control worked as expected and it was very maneuverable (when there wasn't lots of drag from the over kill tether)
-Buoyancy and stability were just fine.
-The tether is slightly buoyant (with another pair it sank)
-No leaks (only 5ft deep mind)
The bad:
-The cheapo camera was just way too dark, even out of the water (reject from my FPV projects, i only used it as it was 5V and could work off an ESC BEC)
-The LED caused flair on the GoPro housing, making the camera worse.
-The water where i was flying was just too damn murkey anyway!
I'm now fitting a known better camera, separating the camera and LED further and doing some other frame refinements. Plus i'm gonna look for some better water to test in! This is only the start!......
