Controls on the cheap. Confused about power source.

[Hex]

Hey everyone. Sorry if this is long but I'm getting it all out of the way. I'm building my first ROV and this is my first project of this type. I've never even soldered before so I'm picking that up as well. I've always had a fascination with electronics but have never actually created anything, so I'm throwing myself to the wolves here. The main reason is that I live near a very secluded, undisturbed, unfished, and THRIVING lake that is overflowing with wildlife. The water is crystal clear if it hasn't rained in a few days, and marine life can be seen out as far as the eye can see. Here is a picture and a short video of what I'm talking about. I did this with a GoPro Hero3 underneath of a large bobber on a fishing pole. Its not uncommon to see VERY large catfish, carp, bass, etc swim right up to the shore while you're standing there.

Here is a picture taken topside while the camera was in the water. All of those black spots are hundreds of fish.

And here is a small highlight clip I have over the 90 minutes of video I took that day. I have 3 or 4 of these highlight clips, some showing some rather large fish. The water is roughly 10-12 feet deep on the first portion of this video. You can still see the bottom crystal clear.


https://www.youtube.com/watch?v=GLjgt1Wm_M8

My current plans for my ROV are to use 3 1100 LPH bilge pumps with props, two forward facing for forward/reverse and one vertical for ascend/descend. I'll be using DPDT relays and a joystick using this schematic:
http://www.homebuiltrovs.com/howtojoystickdpdt.html

The Joystick I purchased is here:
http://www.ebay.com/itm/310570260430?ss ... 1439.l2649

I'm using 2 100 foot Ethernet (Cat5) cords for a tether. One for controls, one for video (I'm not sure if I can stream 480p video on a single twisted pair at 100 ft). I'll be doing a sort of french braid with a buoyant material to keep the tether as neutral as possible. My confusion comes in powering it. The current plan is to use a couple of 3500 mAH power cells that are mounted on the ROV itself. They will provide the power and ground directly to the relays as well as the main source of ballast. So I'm wondering about the actual controls. Where will the power come from that is sent through the joystick and down to the relays? Do I need to have another battery pack mounted in the controller? How much voltage/amps do I need to send to the relays through the tether? I'm very confused on this part, and any help is greatly appreciated.

[rossrov]

Gidday Hex. Just had a look at the illustrations. One terminal of each relay coil can be connected to the battery positive in the ROV, provided the coil voltage is rated the same. 12 volt battery 12 volt coil. When the joystick is moved off-centre, the other relay terminals connect to ground or battery negative through the joystick switches, thus energising the relay.

So the green wire would connect to the "main power feed" in the ROV. The tether will contain 7 wires for the switches and one for the common, which connects to the black in the stick illustration.

"Voltage drop" over the tether will mean that as the tether gets longer, or as more relays are switched in, there will be less voltage at the relay coils, the result being that they will not pull in properly. Experiment and measure the coil voltages.

The only disadvantage that i can think of compared to having a separate battery in the topside controller is that if the tether gets any water in there will be a more rapid corrosion occurring.

[Hex]

The tether itself will be sealed inside and out. I'm going to strip the wires bare and seal them in epoxy so water cannot penetrate the tether. The tether itself is just ethernet cords that I picked up for like 8 bucks each.

So now I've got my bilge pumps. 1100 GPH. I picked up some prop adapters and I'm putting 52mm props on them. I've got the relays sorted out just need to start soldering.

My next question is about the batteries. How much of a battery will I need to run here? My original plan was to run a pair of 2600 mAH batteries. The motors should draw about 4 amps each. I figure these would last me about an hour to control the 3 motors and camera, and about 45 minutes with the LED lights turned on (on average). The ROV won't be constantly moving. I just need to use it to reach a few areas with abundant marine life and then I'll park it there for some good video. Now I'm looking at a pair of 5000 mAH batteries that I've found for $37 each. This would technically give me around 2 hours of battery life, correct? I'm really just interested to see what the average battery size most people are using and how long this typically lasts them.

Also, for the LED lights, how many watts does one typically need for a 20-30 foot dive in fairly clear water? I can get 12v 9 watt LED flood bulbs for 10 bucks each and are rated for roughly 500 lumens each.



Honestly, there should be a big FAQ for this type of stuff. There are tons of how-tos out there, but not very many with detailed explanations. Most sites are filled with people that have already done this type of thing and are showing off their project or looking into further improvements. There isn't a lot of information out there to help the beginner spoon-feed himself.