My project is to control a buoy underwater depth of 300 meters to 500 meters maximum.
At first, I will connect a cylinder to an empty buoy, then when it reaches the depth, I have to take it up again but wirelessly, so I’ll press the button on my controller above the surface to release the cylinder oxygen, so the buoy it will heave the cylinder above to surface.
-I’m looking to build a simple controller, Any kind of controllers, but without using wires.
- is it possible to create this kind of controller ?
Any idea or suggestion would be really appreciated.
Water is a great shield against radio waves, so they can’t be used practically for under water communication. For wireless audio communication under water, divers use ultrasound.
There are companies selling under water data acoustic modems, but they don’t have price on their website, so it probably cost a lot. Diver communication systems are also around 1-2k$ and i don’t know if they are capable of transmitting up to 500m.
I think your options are: 1. buy a diver communication system capable of transmitting 500m(if such thing exists) and couple it with an acoustic modem, 2. get a pair of high power ultrasonic transducer and make your own modem.
BTW water at 500m will give you a lot of pressure, what material will it be made from?
It’s probably better to have both of them under water, but I don’t think it will help that much; I searched around the internet and according to some old rc forums: 2.4GHz rc transmitter will give you a range of 10cm, a 75MHz rc transmitter can give you around 2m, a 75MHz 1W transmitter can give in theory a 10m range, military submarines use an ultra low frequency(~30kHz) band to communicate and they can go under water a maximum of 20m to transmit.
I think using a tether or ultrasound is the only way for reliable under water communication; in clear water maybe using visible light can be an option.
Given the problems associated with communicating underwater (notali’s comments agree with what I know), I wonder if your needs would be met by a pressure switch that would trigger at a hydrostatic pressure calculated for your intended depth?
Much would depend on your necessary depth accuracy as well as pressure switch accuracy. You could calibrate it on the surface with a hydraulic hand pump and gauge.
Another idea would be to see what the scuba community has for both surface communication and for digital devices (like dive computers) that could output depth and trigger your switch.
yes, that what I’m saying, both of them are underwater receiver and the sender.
Garmin sonars, using 200hz so if it possible to build that remote so i can active my underwater button.
is it ?
I checked Garmin’s website and they make sonars with 200kHz sound waves, they also sell ultrasound transducers separately, some of them capable of sensing 500+m depth, so I think it is possible to buy two transducers, figure out the pinout and build a drive circuit for them; but I would buy a transducer from an ultrasonic cleaner instead, they are cheaper and have a lot of power. The reality is, that if you want to buy a ready made solution you have to pay thousands or tens of thousands of dollars; or with a bit of experimenting and dedication i think you can succeed with a much cheaper DIY device.
I would strongly suggest to use a tether or a depth sensor to automatically trigger the oxygen valve.
You can encounter a lot of issues with ultrasonar/sonar underwater, as the signals could reflect on obstacles and such.
A tether would ensure you to be in direct contact with your device, you could use it to have a proper bandwidth if you want to have sensors/cameras and such in your device. It will also assure you a Plan B, in case your oxygen valve doesn’t work properly and do not trigger.
Sorry for the late reply.
You can buy transducers from ebay(link) cheap.
There is multiple way to build the transmitter and receiver circuit based on the chosen modulation technique.
I don’t have much experience with analogue circuits, so I can only give a rough overview, how I think this should be done:
The simplest form of modulation is Amplitude Modulation(AM), but if your signal is digital then it becomes a special case of AM called: Amplitude Shift Keying(ASK), basically this means, if your bit you want to transmit is 1 you turn the oscillator on, if it is 0 then you turn it off.
The transmitter:
you have a digital signal from a microcontroller, with this
you can turn a sinusoidal oscillator on and off, you can make oscillator with an 555 circuit+some filtering for example, or using a PWM output from+filtering from an MCU.
this oscillator is not powerful enough to drive the transducer, so you have to build a power amplifier.
The receiver:
This part is trickier, because depending how far you are from the transmitter, your signal strength can vary greatly, so you have to build an
Automatic Gain Control circuit, then you can
demodulate the signal just like in AM demodulators
with a bit of signal forming you can feed this to your MCU inside the buoy.
The AGC need some time to adjust for the signal strength so you have to transmit a preamble, and encode your data for a more robust format, luckily there are some arduino libraries which can help you with that(VirtualWire,RadioHead)
The above setup is just a transmitter and receiver, if you want half duplex communication, you have to include the transmitter and receiver circuit in each device and switch between them, full duplex communication will increase circuit complexity so I don’t recommend it.
Notes:
This is a complex project, you need knowledge in radio communication and circuit design.
I’m sure you can find people who can help you design these circuits, but try to come up with a sketch first for this system and do your research in the relevant topics.
Safety:
These ultrasound transducers generate very loud soundwaves, just because human ear can’t hear it doesn’t mean it can’t damage hearing, so when you test it on air minimize the transmission power.
Wireless transmission is not as reliable as cable, so if you don’t want your buoy to stay in the abyss, set up a communication timeout, which when exceeded the buoy will come up automatically.
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