laptop control

[fireslayer26]

Would the step up converter need to be on the ROV or could it be topside with the control setup? Why does it need 48V when it operates on 5V? Sorry, I'm not that versed on things like that. Could I power everything with a battery like this: http://www.ebay.com/itm/Power-Sonic-Pow ... 2580698843

I plan on using 12v compatible brushless motors, esc's, led lights, camera.

http://hobbyking.com/hobbyking/store/__ ... verse.html
http://www.ebay.com/itm/190744465932?va ... 1423.l2649

[njs552]

The step up converter will be on the surface with your control setup.

It needs 48v because of voltage drop. When you supply power through metal wire, the wire has a very small internal resistance. The wire will resist current flow, and so your voltage will drop as you require more current. Because of Ohms Law, you can send 48v, at 350mA over cat5, and still have about 40v on the other end of a 300ft cable. If you did that with 12v, you would end up with much less than 12v after 300ft.

How long is your tether? Depending on how long it is you may be able to get away with some heavy gauge speaker wire and a 12v battery. Otherwise you will need batteries in series at the surface, and a power converter in the ROV.

Do you know how much current yo system will require at 12v?

Thanks,
njs552

[fireslayer26]

I haven't added it all up yet. My tether will be 100ft max.

[njs552]

OK. Are you going to power your ROV from the surface or with that 12v battery inside?
If you are going to have an onboard battery, then that battery should be fine.

Thanks,
njs552

[fireslayer26]

I was planning on powering everything from the surface with a large 12v battery like the one above or maybe a car battery. Possibly through an appropriate sized speaker wire pair. Or a spool like this: http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0954772777

Onboard the ROV I would have a DC step down converter for the Arduino to supply the needed 5v.
http://www.ebay.com/itm/LM2596-Digit-Di ... 53fa84d82f

[njs552]

OK. You will probably need more than one battery in series to supply enough current at a good voltage.

If your typical ROV current draw at 12v is about 8A (not unreasonable as long as thrusters are power limited), then if you supplied 12.5v at the surface, and pulled 8A, your voltage at the ROV would drop about 50% to 6v. That would not be good for anything, let alone speed controllers that need at least 7v to work properly.

My suggestion would be to have a few 12v batteries at the surface, and then have a DC to DC converter to step the voltage down to 12v.


The DC converter to 5v would work, but you can also supply it with 12v on the Vin pin.

Thanks,
njs552

[fireslayer26]

Oh ok, so the board has its own step down converter. So I can just supply the 12V to the power input plug via a 2.1mm center-positive plug, correct? Do you think a Lipo 6s battery like this one would be sufficient at the surface and then use a DC stepdown on the ROV to regulate it at 12V?
http://www.hobbyking.com/hobbyking/stor ... _pack.html

[fireslayer26]

Does this diagram look correct for what I'm trying to accomplish?

[njs552]

That looks perfect.

One the topic of LiPo;s as a power source, you would be better off putting 6 or so 2000mAh 3S lipos in parallel in the ROV so you would basically get 12000mAh for somewhere around $50. It is cheaper to buy the 3S cells and use them in series or parallel than to use the 6S cells which will also require an expensive balancing charger.

Thanks,
njs552

[fireslayer26]

Great, thanks for the info. When will your friend be releasing the next software update with the integrated video? Is the only way to get video with the Pi in his setup. Or can you get a video feed without using the Pi?