I am working on a special project and need some assistance. Our non-profit organization is developing an acoustically-activated ropeless crab trap to eliminate the entanglement and death of whales and other marine life. We have developed the release mechanism, to a point. The system has to rely on an acoustic pulse sent to the trap and a device that reads the frequency and instantly sends a 3V spark to an actuator. We are looking for advice or an individual who can help us with the acoustic-to-3V spark, and this would doubtless require a custom circuitboard.
Stan
Bluecology
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I am working on a special project and need some assistance. Our non-profit organization is developing an acoustically-activated ropeless crab trap to eliminate the entanglement and death of whales and other marine life. We have developed the release mechanism, to a point. The system has to rely on an acoustic pulse sent to the trap and a device that reads the frequency and instantly sends a 3V spark to an actuator. We are looking for advice or an individual who can help us with the acoustic-to-3V spark, and this would doubtless require a custom circuitboard.
Stan
Bluecology
<snip> email address removed to prevent spam.

What is the spark from a 3V source supposed to do? Why would you imagine that it would do anything at all? One might suspect that since anything less than 50 VDC is generally considered safe that 3V would be insignificant.

 

Here is our situation. The entire release mechanism, miniaturized, will be integrated into a small buoy that is attached to the 100' retrieval rope coiled on the trap.The vessel sends an acoustic pulse that is picked up by a microphone inside the buoy. Through the circuit board, the audio has to ultimately create the spark, via a 3V battery. The spark will activate a 3V actuator (which we have), which in turn releases a spring-activated armature that releases the buoy and send it and the buoy and rope to the surface. The entire project is dependent on the acoustic signal initiating the 3V spark that releases the buoy. It's a lot to envision but once we can create the spark, we are closer to a prototype.

 

The entire project is dependent on the acoustic signal initiating the 3V spark that releases the buoy

You say "spark" which generally means a electrical discharge through air, but it seems like you mean a pulse of current in a circuit.
Is that correct?

 

I see no purpose in having any sort of sparking happen. An acoustic signal can trigger an electrical pulse, or simply cause a switch to operate to initiate the mechanical part of the system.
The serious challenge will be the transducer that hears the underwater signal and generates an electrical signal. An underwater microphone that works at 100 feet below the surface is not a small issue.

 

Thank you both for the information. We have the underwater microphone that operates to full service at well over 100'. This has been a two year project for us, not only to design, build and test, but to placate the fishers as well. Most of this has been done with research, much as I am doing here with you, and very, very much appreciated. You have indicated that an acoustical signal can trigger an electrical pulse or cause a switch to operate. How can I secure the detailed information on how this is done, or find an individual who can instruct us?

 

What is the output of the microphone when it hears the trigger signal?

What steps ensure that this trigger signal is not inadvertently produced by some sound other than the intentional signal? You probably don't want an engine backfiring or someone dropping something on the deck releasing your traps.

What type of signal does the release mechanism need in order to release the bouy?

It sounds like you just need a circuit that listens to the electrical signal from the mic and produces the needed electrical signal for the release mechanism.

How easy or hard that is will depend, more than anything, on the waveform produced by the microphone and how much conditioning is needed in order to achieve acceptable false-positive and false-negative rates.

 

It appears that cost will also be an issue, as well as complexity and re-use. So the system will certainly need to respond to only one frequency, and that frequency must be different from noise such as boat motors or whatever sounds that underwater creatures make.
Given that you already have the underwater microphone, it will be important to know what frequency it is most sensitive to, because that may be the best choice for the trigger sound signal. The real challenge will be to create a system package that will be reliable enough to survive repeated use and not leak at all, while still being rugged and inexpensive. Operation on only three volts for the power supply is more than a small challenge, as well.

The amplifier will need to be frequency selective, and probably the most reliable scheme will be tuned circuits using a coil and capacitor resonant arrangement.

Do you have any person who is electronics competent on your team for this project??

 

Whales, boats etc produce quite a range of frequencies, so I think it might be better to signal to the mini-buoy with coded sequences of acoustic pulses (like Morse code), rather than analysing received frequencies. The hydrophone signals would be analysed by a microprocessor to reject spurious signals and verify the code.

 

Whales, boats etc produce quite a range of frequencies, so I think it might be better to signal to the mini-buoy with coded sequences of acoustic pulses (like Morse code), rather than analysing received frequencies. The hydrophone signals would be analysed by a microprocessor to reject spurious signals and verify the code.

Any logic scheme to decode signals will both add complexity and power consumption to the receiver end of the project. Unless you have some scheme that can do it without a processor constantly drawing power.