How to electrically release a buoy ?

[Diver0001]

Minutes? Or months?

Yes, that's the question that needs answering.

If you are thinking of using radio signals to control it....basically forget it. RF does not work well under water. Your controller will have to be either wireline or fiber to be dependable.

I'm not clear how far away he needs to be from the buoy in order to trigger it, but you're right. RF has a limited range under water. If it could be a wireline then the solution becomes child's play because you can throw together a decent electromagnet with a mechanical switch from stuff you probably have laying around the house.

R..

 

[Akimbo]

How deep and what size buoy? You could include a simple solenoid or motor in the same housing as your acoustic receiver electronics that moves a fixed-magnet to avoid mechanical penetrations. The magnet on the outside would secure the end of a Pelican-hook style mechanism. You could also use a solenoid valve controlling a compressed gas source if you need a big buoy at a shallow depth.

explosives - YES!

That's waaaay more fun than my suggestions, but probably less reliable. I had to replace tons of them over the years. They are probably great until you put them underwater. There're also problematic to test.

 

[gfaith]

Normally closed spring held solenoid, released with electromagnetic action (opened). Now you need to trigger the solenoid and radio waves don't travel well underwater. Perhaps you embed a low voltage communication pair inside a cord that is topside.

edit: I see the radio was mentioned while I was typing.

 

[KeithG]

There're also problematic to test.

Only if they do not go off...

Successful tests are easy.

 

[KeithG]

If you are thinking of using radio signals to control it....basically forget it. RF does not work well under water. Your controller will have to be either wireline or fiber to be dependable.

What is the range of (ultra) sonics underwater? Liquivision had some stuff on the market. What was its range and battery burn?

I also vaguely think I remember bumping into some commercial rf underwater modems. I believe the working range was a few inches - the idea was to use a ROV to bump into underwater stations and gather data. I could be confused about all of this...

 

[Externet]

Thanks, gentlemen.
lowiz: Those hooks were unknown to me, good to know they exist and will evaluate how to activate them electrically if there is no servo/solenoid driven in the market.

giffenk:
- About 10 watts for half a second if that does it. If not enough, I can parallel more batteries.
- Not a brutal force. The buoy is 2 litres. About 20 Newtons pull force.
- Marine current of less than 0.5 m/s
- Area of the buoy about 0.03m2 - Just a 'marker' type about 15 cm diam.
- The buoy remains tethered from its anchor site after its cord is released from bottom.
- Depth of anchor, release mechanism and held buoy is 4 metres.
- Operational battery life is one month.
- I have no clue on Mythbusters

Diver0001:
It is held in place for 7 days, Not consuming battery power except minimal for the receiver, until the receiver triggers the mechanism for a couple of seconds.

 

[Schwob]

If you are thinking of using radio signals to control it....basically forget it. RF does not work well under water. Your controller will have to be either wireline or fiber to be dependable.

Might have to be sound under water. Device could trigger on a sound pattern match.
But definitely needs more info to say much about mechanism / actuator.

 

[Akimbo]

Hmmm, that's pretty shallow. Is this a one-time use and how far offshore?

 

[Aviyes]

Something like this? Acoustic release - Wikipedia

 

[Externet]

Thanks, gentlemen.
Akimbo : For a weekly release and years of operation, 1Km offshore.

Yes, Aviyes. Something like that. The mechanism is what am after, resettable as in a snap shackle, instead of fuse-melting.

The snap shackle that uses a pull pin, the pull pin could be longer made of magnetic stainless, (series 4xx?) becoming the core of a solenoid. And the solenoid being fully waterproof-corrosion proof is another hurdle.