For a long time, I wanted a fishfinder, but there was no money for it (as a student) and there are big doubts about its need and functionality. Since it shows the bottom relief only when the boat moves, and when it stops, it is almost useless for anything. Having searched the net for information on fishfinder, I came across "Simbia CPS - 200", this is an annex to a PDA or a computer, Bluetooth or wire, but from itself, it represents the simplest echo sounder but is expensive. And for such money, you can buy a much better thing ..

After that, I thought about how to make this myself and I had some interesting ideas .. about them later .. The biggest problem is that I do not have the patience for any serious projects, and this all the way I want to build .. so I decided to take this topic as a graduation project, tk. I study in the last year (specialty Radio Engineering).

The idea is this: 1) Firstly, in my opinion, it is necessary to take a ready-made sensor (emitter-receiver), single-beam, it is inexpensive, the truth must still be looked for.

2) Next, I need some generator to emit a signal through the emitter (I do not know the signal parameters yet), but it's kind of like a rectangle with a frequency filling of 200kHz

3) from the receiver, the signal is removed, amplified, fed to the ADC, and then to the controller, which gives all the Bluetooth module, which transmits data to the PDA.

In the PDA, a vertical strip is constructed from each input signal, then shifted, the next one is built, shifted ... well, and so on, as in a conventional echo sounder

The chip of my device is that the top of the echo sounder is attached to the axis, which allows it to be manually or electromagnetically deflected from the vertical position and thereby scan the bottom when the boat does not move anywhere. Yes, to track the angle of the rod, an angular position sensor is required.

Ie in this mode, not only the echo signal is transmitted to the PDA, but also the angle value. By turning the sounder from side to side it is possible to construct a triangular ecological chart on the PDA screen (the principle of operation in the figure, for the scanning angle 120 and 90 grams) is most likely to be taken as 90 g. According to the article that I read here, it is possible.

At the moment I have some problems that I solve and study, for example, I learn C ++, I understand echolocation

Well, in the course of development I hope for help and tips
The plans are as follows: by the middle of March, it is necessary to pass the Task and the beginning of the diploma, and the surrender and protection somewhere at the end of June, well, in the summer, you want and experience the finished device .. or earlier... [img:center]https://ibb.co/fG1Poz[/img]

As for the angle of incidence, I did not think about the exact angle, the same thing happens with ordinary fishfinders with a sharp change in depth (pits, hummocks, stones) and as I understand the echo sounders, in this case, they work, although probably the signal level still falls. And the material of the bottom is not a mirror, I think that when the wave falls at some angle, for example, to sand, it will scatter in all directions like light on a matte surface, as if falling under a straight line, although under the direct course it is better. To compensate for the difference, you can increase the gain by increasing the angle. In the adult sonar, an increase in gain is applied depending on the depth. that is, the levels from objects located at the middle depth and on the large are programmed to be programmed.

About the interference did not think ..

In this regard, I remembered another characteristic that should be selected: it is the maximum depth .. for modern fishfinders it is "Maximum depth 270 meters, power 200 W (average), 1600 W (peak)"

Do we need such power ..? It seems to me that people who catch at such depths have a good boat, a motor, etc. And my device will be bought by a person who is well acquainted with electronic, who is an amateur in fishing, and catches on much lesser depths, for example on lakes, rivers, on an ordinary rowing boat, and the bottom scanning mode is very useful .. which is interesting to study the bottom relief, to follow the fish ... Therefore, the maximum depth I think to take 100 meters. (But this must be considered .. express your opinion)


And Bluetooth has chosen because I hate wires ... in my opinion, it will be very inconvenient to drag on fishing with a PDA or laptop when wires run from them. A Bluetooth is now everywhere .. on any normal pda there is a Bluetooth, and if not, then you can buy an inexpensive module .. And the only alternative to it is WiFi, but that I even less know about it. I know only that there are more speed and range (it would be useful), but on my PDA, it quickly discharges the battery...