Hi,
i am working on a project in which i wanna know the position of transmitor that is in the water. I would like to create a rc boat that will with help of sensors find the "lost object". What kind of sensor should i use and how to determine angle and a, x variables. Is this even possible?
Best regards
Probably the easiest way is to use visible light and a camera. You don't get your variables but in my opinion you just need a direction for your task, the distance and the depth are not relevant until you get to the object's position.
This might work but it depends on several parameters you didn't provided: how big is the search area? Is the water clear?
One drawback of my solution: You cannot use an Arduino for the task because it has much to less power for it.
Radio works only for very short distances underwater.
Google for 'sonar'.
a, x variables?
I live near see and the water is quite clear here. Depth is around 20m. I would use a some kind of sonar but i would have transmit some kind of wawes from object and then pick them up with sonar. Any ideas how to do that?
Use a sonar transmitter module.
So the object you are finding is something that you have created, and it will be actively transmitting some sort of signal yet to be determined? Basically a beacon that you want your boat to go to the location of? And you're doing this in the wild.
If the water is clear, an omnidirectional blinking light for a beacon wouldn't be difficult. Using sonar would be at the mercy of the sea and bottom for alignment, and you'd need a much more powerful detector than any dinky hobby grade item.
The problem is then how to control the boat toward the beacon in choppy waters. I don't think your boat would be very large so it wouldn't have much stability between readings. It's a difficult project.
Might be easier simply to give both beacon and boat gps coordinates and have them coincide instead of literally finding each other.
Yes i was thinking about gps. I am wondering how does it work unerwater and how accurate can it be?
GPS does not work underwater. It often won't even work under trees.
Assuming your "transmitter" is acoustic (since only VLF radio will work at all under water of any depth and that requires a big antenna), you could have two pickups (one on either side of your boat) and compare the signals you get from the two pickups. Phase (or time difference) could give you a heading. You could also have one sensor (transducer) that you rotate and look at the signal strength although reflections can give you some very strange results (if your transmitter is around behind a rock or something, the signal will appear to come from whatever is reflecting the signals). The only other option really underwater (and this requires relatively clear water) would be an optical transmitter with a sensor on the boat you can rotate to find the signal (light) and steer that way. Different colors of light are absorbed differently in the water and some have better range than others. In muddy/murky water, sound is going to be your best bet.
Use a continuous audio frequency in the sender whereby a half wave in water equals the distance between the two sensors on the receiver. A phase comparison will show a peak when aimed at the source and a null at +/- 90 deg. A Teensy V3.2 with dual synced ADCs would work nicely in the receiver and a class D amp in the sender driven by an opamp sine wave oscillator.
Use a quarter-wave separation then you get unambiguous direction too.... Assuming
you can get a clean pair of signals to send to a phase detector.
I was assuming that the sensors were hemispherical so that an initial 360° would send you off in the right direction.
You could also use three sensors in a delta configuration at some spacing. The Teensy V3.6 also has dual synced ADCs but also includes hardware FPU. A rather exotic phase analysis could be performed including digital filtering on the received signals and direct calculation of the steering angle error.
The OP could model the setup in air, with appropriate dimensional and frequency scaling, and work out most of the bugs before putting it underwater.
I used this kind of analysis in the mid 80's with a Gateway 486@25MHz and a 10MHz half-flash digitizer on a home-brew GEOS satellite receiver system.
