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Remote power shut off?


(undersearobotics.com) #22

Hey Tim, have you had a chance to test out your battery shut off yet? Rusty suggested that we could wire a few in parallel to double the current capacity so I bought two from Pololu.


(Tim Pierce) #23

The battery gets here Friday. I still need to order a charger for the battery. As soon as I have them both, that test will occur. It looks like it should work fine though.


(Tim Pierce) #24

Tested this out today with revision 2, with the correct xt90 connector. It works great, and so far with the thermal camera shows no real heat output to worry about while in use. I do need to replace the barrel connectors I used as they are slightly too big, but overall I am quite happy with it, and most importantly the new rov didn’t explode or catch on fire!


(undersearobotics.com) #25

That’s great news Tim! Thanks for the update! Did you test the ROV in the water or on the bench? No doubt the thrusters will draw more current while running in the water.


(Tim Pierce) #26

On the bench at the moment. Significant portions of the ROV frame haven’t been printed yet,


(Tim Pierce) #27




No motors connected this time, but the barrel connectors are fixed now. I can bring up and shut down main power from that external switch, so far without issue or problem. The whole assembly doesn’t take much more room than the stock cable adaptor near as I can tell, seems like there should be plenty of room for it even in a stock length battery tube.

My 3d printer has been busy printing commission work so the sideplates and bottom plate are still sadly missing.


(undersearobotics.com) #28

I suspect that with all 6 thrusters running in water the load on the relay will increase exponentially. If it gets too hot you might try running two of those Pololu boards in parallel.


(Roar) #29

Some update about Pololu project.

Will it work with two Pololu board in parallel or do we need several in parallel.

Someone who has tested it with all 6 thrusters running in water?


(Tim Pierce) #30

It seems to work fine with just one of the bigger ones with all 6 motors going.


(Roar) #31

ok,will it be hot?

I thinking to have my Pololu in the main tube and connect a small relay and send down 5-12 volt to activate the small relay. then i have a ON/OFF button on surface. (i will use the same wires as Fathom-X boards use)

it is better to only have one button on the surface to power up everything.(laptop.monitor,Fathom-X boards,Bluerov2)

I thinking first to buy a 12v/80amp relay,because it will not be hot.but i don’t know If that is enough.


(Tim Pierce) #32

It doesn’t seem to get noticeably hot. I’ll take some infrared pictures of it when I test it next.


(Roar) #33

ok
I have searched after small 12V/24V relay and i have found 1 on https://www.aliexpress.com
this relay can switching 120 Amp.

Size of relay is 28mm x 27mm x 25mm,can fit into main tube or battery tube.

I will buy it and test it,120 amp is more than enough to bluerov2.


(Marcus) #34

Hi all,
I’m obviously missing something, but at rest, I thought the only device drawing power was the Pi (and anything else connected to the Pi)? But I’m guessing given the discussion that the ESCs also draw power? Any idea what sort of load? I had a look for the AfroESC specs but couldn’t find anything.

I’m just wondering for myself the tradeoff between a simple switch on the BEC for the Pi to save most (maybe) of the power draw, vs the options discussed here for an absolute power cut.

Cheers,
Marcus


(Rusty) #35

Hi Marcus,

I believe the ESCs draw about 0.5 Watts when they aren’t running. The microcontroller and other circuitry draws about 30 mA at 5v, and since it’s powered through a linear regulator, it uses the full 30 mA at battery voltage (16v). So that’s 16*0.030 = 0.48 W.

-Rusty


(Marcus) #36

Great, thanks Rusty. I assume thats per ESC, not total? So you’d be using about 3 watts at rest.


(Rusty) #37

Marcus,

That’s correct, 3 Watts total at rest. It’s quite a bit. There are potentially some software changes that can happen on the ESCs to reduce that.

-Rusty


(Roar) #38

I have now install the 120 Amp relay and is working,i have now a on/off button On the surface.

I send 24 volt down to the bluerov2,through same wire as Fathom-X Board to activate relay.

I use 170 Meters seabotix cabel 8.9mm,all wire inside has shield and two of wire is 16AWG (i use these to Fathom-X Board)

I have also make a charge cabel,i dont need to take out the battery anymore.


(Jacob) #39

That’s a really sweet modification, thanks for sharing! The control box looks great.

-Jacob


(Doug) #40

Why don’t you simply switch all the control power off with the Blue Robotics switch. i.e. switch on / off tether interface, Pi Computer and Pixhawk. Problems with high amp relays gone. The only thing left to draw any energy are the built in esc’s for thruster control.


(undersearobotics.com) #41

I think the principal objectives of being able to turn off power in the ROV are to prevent unnecessary battery power loss and to render the ROV “safe” without having to open a housing. Turning off power to the control systems might meet one of those objectives but not both.