Hi All,
I'm trying to wrap my head around the components/technology to be able to have a sensor that can detect the water depth at its location and temperature and remotely/wirelessly send the information back to a receiver.
The sensor should be self-contained and as small as possible.
I'd like the sensor to connect to a fishing line while being dragged by a boat a different depths. I'd like to be able to find out real-time, how deep that sensor is.
There's a product that does this (although expensive) and it is not much bigger than its AA battery source.
I don't know the technology behind it but it uses a transducer and receiver.
I'm hoping there are simpler methods with a small profile (on the sensor end).
The Smart Troll uses ultrasonic signals to transmit data, which for underwater use is advanced technology and not something that could easily be done with Arduino.
A pressure sensor suspended by an electrical cable will accurately report its own depth and would be easy to implement. Pressure increases linearly with depth, and a pressure sensor is almost certainly used by the Smart Troll as well.
If you want something to attach to a fishing line that acts like the Smart Troll, the Smart Troll may be your only option. Keep looking, though.
The absolute atmospheric pressure (barometer) of the air is about 100kPa.
The "hydrostatic" pressure is that plus the pressure by the water, which is about 10Pa per meter depth. At 10 meters, the total pressure is 200kPa.
In bars: the air at sea level is 1 bar absolute pressure. Every 10 meters, another bar is added to that.
Suppose that you want to measure up to 20 meters depth, then you need a absolute pressure sensor of 300kPa.
The MPX5700AP costs about 20 dollars and go up to 700kPa.
It does not need to be in contact with water. A flexible housing will bring the pressure to the sensor.
The VirtualWire or the RadioHead in RH_ASK mode can retrieve data from noise in a very good way. That can be wireless, with light or laser or with sound. https://www.airspayce.com/mikem/arduino/RadioHead/
However, modern techniques are much better.
Then you need good transducers. The transmitting transducer should be able to withstand the pressure.
If I would make it, then it would be two boxes of at least 5x5x5 cm and I guess that I can make it work up to 2 meters depth and it costs 100 dollars.
If I had to cap the range, it would be no deeper than 100ft in fresh water. But the sensor would be monitoring between probably within 5-30 ft... but the boat would be moving, so it wouldn't be simply dropping the sensor vertically. If I could do something similar to Smart Troll at a fraction of cost, I'd consider it.
A moving boat does not matter. The pressure is how much water is above the sensor. You will still measure the depth.
It is a combination of different disciplines and people with skills are needed to make something like that.
If someone could do something similar at a fraction of the cost, then would already been done. I tried find something similar on AliExpress, but I can not find it.
Correct. Boat speed and the amount of line out will generally affect the depth (among other things as well). I'd just be looking for the actual depth. While trying to be as streamlined or aerodynamic (if that applies to water) as much as possible.
It looks as if this reads data from an existing transducer but would this be the sensor that is submerged to read the depth or is on the receiving side connected to the transducer? Just to clarify, I'm not trying get the actual depth to the bottom, just the depth of how deep my line is in the water column.
I agree that the Bernoulli effect will cause errors but the fact that the sensor is not hanging straight down will cause no problem. Water head pressure will be the same regardless.