Probably people too…
Where did 150A come from. The current would depend on the conductivity of the water and the distance between electrodes. You would probably have to generate enough volts to be pretty lethal to anything.
I don’t know how an echo sounder works re sharks
A battery that can do this will cost thousands, two I checked, $2199 & $3099.
What will this signal be, what kind of signal will ward off a shark ??
Assuming it will be in the sea; sea water is conductive and corrosive.
Water also limits the propagation of RF signals, but if the shark is repelled by Audio, like whale song then propagation would be much better.
To adequately advise you what will work more information is needed.
EDIT: Then theres battery life. The battery I check would last about 2 or 3 hours before needing recharge.
The product that I’m trying to mimic is called a shark shield. The output is a 150amp pulsing signal that happens every half a second so it’s not dangerous. Its a cable taht dangles off your leg while you swim
Hmm I would not like to ‘experiment’ with these currents / voltages as an amateur maker.
I found these links for commercial gear – at least if the product (or the shark) bites you, there is a legal process to follow for equipment ‘not suitable for purpose’ etc etc , but if your own home made stuff fails or injures you or anyone else all bets are off.
p.s. I have been on the painful receiving end of a high voltage and potentially high current electric shock - not pleasant at all, and I still have some marks to remind me 40 years later.
Just looked at the links for “Shark Shield” and nowhere could I find any reference to 150A.
Sure that couldn’t be 150Hz could it. Maybe short bursts of 150Hz every half second or so might do the trick. I just don’t know.
So the only solution I could possibly give is purchase one of these things. And I hope it works and you don’t have to sue someone from a hospital bed or worse.
Me personally, I have a deal with sharks. They stay out of my bath tub and I stay out of theirs. There again I always was something of a dry land person.
Historically, our customers have told us that feeling the electrical field provides comfort by knowing the device is active. You know our devices are active and working!
To produce a protective electrical field of an effective size the electrical signal needs to be strong. When accidentally placing your hand near or on the antenna the electrical field may cause stimulation of the surface muscles of the skin. This may differ for each person and the feeling is similar to that of a static electrical shock.
The amount of stimulation is minimal if accidentally touching the antenna while it is fully submerged. The reason for this is that the easiest path for the electrical signal is to flow, is between the two electrodes through the water, rather than through the user.
A higher amount of stimulation may occur if the user accidentally lifts one of the electrodes out of the water with their hand or other parts of their body. The reason for this is that the user then becomes part of the current path between the two electrodes.
For comparison’s sake, Ocean Guardian only emits up to 85 volts of electric power; whereas electroconvulsive therapy, used to treat depression, would be between 225 volts and 450 volts. Therefore, the Ocean Guardian shock will only be light and would not affect you in anyway other than a little shock.
*$749 * While Shark Shield can deter a shark from attacking, it won’t do so every time. The most recent study of the device by scientists at the University of Western Australia (UWA) found it prevented great whites and tiger sharks from attacking most of the time, but it wasn’t always effective. An earlier study by the South Australian Research and Development Institute also found the device was effective in deterring great whites, but noted it didn’t “deter or repel this species in all situations, nor did it repel all individuals”.
And user reports back this up. A South Australian abalone diver told CHOICE he knew of two people who had been attacked while wearing a Shark Shield.
But while Shark Shield has been shown to be effective at least some of the time, it turns out not all electrical repellents are created equally. UWA researchers found that electrical repellents compacted into an anklet were ineffective at repelling sharks.
The User Manual says 150A, 11.1V Li-ion 3 cell, 6-7 hours usage, pulse every 0.6s. Generating an electric field about 1 metre from two electrodes.
It works in sea water because sea water conducts electricity. This current flow generates an electromagnetic field supposed to upset a shark. The field can be optimised by changing frequency, voltage and current.
To build something like the Shark shield for less than the $749 price, optimised to work in sea water, safe to use, meets Australian standards, is water proof, etc; is a bridge too far in my opinion.
Also, a device that works 9 times out of 10; is ok for 9 people but not for the 10th.
The advice from @Murray125532 about the legal aspect is well worth listening to. Approved devices will get support, a DIY project will not.
Thanks for your research I appreciate it. I’m certainly not proposing to be in the water with this thing but I’d be happy to use only as a deterrent on my kayak. Is it too hard to make anything resembling this device. I’m not looking to sell the product I just want something to deter sharks.
Is there anything that will produce such a signal pls
At 150A that is 12750W. Good luck with getting that out of 3 cells that fit into something a little larger that your hand (as estimated from the pics).
That equates to 48A. Which is 2304W. Still a hefty power for 3 relatively small Lithium cells.
85V @ 150A would be a load resistance of 0.6Ω. That is probably extremely saline sea water. I don’t really know what the conductivity of sea water is, i suppose I could look it up but I don’t feel the need.
To me the numbers (all important) don’t seem to add up.
I think to get any meaningful responses a bit more info about this pulse would be required. Such as pulse duration, the repetition period is quoted as 0.6 sec but that does not define the pulse width, The max output voltage, source impedance of the generator and resistivity of the water will affect the current, all values are relevant.
Then there are those apparently small batteries and large wattages. Watts are Watts and you can’t change that.
It would be interesting to find out just what the numbers are and just how that device works. But understandably this info would be commercially sensitive and not readily available. The price would be enough to prevent anyone purchasing and reverse engineering just to satisfy curiosity. There could be patents involved also.
Sorry to appear to be a dampener but someone might have some ideas. Sure, high voltages can be generated fairly easily by discharging a cap through an inductor (CD car ignition) or using a “Sidac” and inductor but at very low currents. It is the 150A that is a bit suspect.
Let’s take the information that is publicly available (because I doubt that you would have any luck getting detailed information from the manufacturer).
“… each pulse in a pulse train has a duration of 2 ms, the pulses in each train being spaced at intervals of 20 ms, and the pulse trains being repeated at a frequency of between 2 and 5 Hz.”
There appears to be three pulses per train, so that is 6ms on time per 20ms. At 2 Hz repetition rate that’s 12ms/s or 8.3% duty cycle. 48v at 1 Ohm is 48 A or ~2300 W. Even though some reports indicate a sine wave is preferred it seems a square wave is used in this case, with very fast rise and fall times. So a 8.3% duty cycle for a 2300 W load is 190 W. An expensive LiFePO4 12v battery might be about 8Ah. That’s about 30 minutes of operation. With two batteries and assuming all that battery power gets to the electrodes (which won’t happen) and a much lower current than you have mentioned, you will get less than an hour of use.