Robbe Seawolf V2

Im starting a thread there just now as i have a lot of ideas and i dont want to start new threads for all of them.

this is the only photo I have of what I bought, it should be here soon


for controlling it all I'm probably going to use a modified version of my ESP32 boat controller with sub functions added on.


I have been mainly trying to work out depth control systems, most of which I have posted before.

the first one will be a pressure sensor, i found this automotive one that had a thread so i should be able to just port it to the outside to get readings.

https://www.aliexpress.com/item/32986724606.html

The second depth system will be a sonar or 2, the first will be a dual transducer version for depth, and im probably going to install another single one in the nose to stop me crashing into anything. I want to eventually put fpv on it and visibility is almost nonextent at the best of times so having something to give me warning of a collision is probably a good idea.. The single transducer has a minimum range of 1.5m so its not ideal for measuring shallow water but the dual transducer will go down to 15cm.

https://www.theassociationofmodelsubmariners.com/t1980-jsn-sr04t-depth-sounder
https://www.aliexpress.com/item/1005001594028046.html
https://www.aliexpress.com/item/1005003199461771.html



Third will be a conductivity probe disguised as a conning tower, this gives an analogue output based on how deep it is and how salty the water is, but it should allow it to just skim the surface to keep the video antenna above the water.

https://www.aliexpress.com/item/1005002748929090.html

And finally il be using the radio RSSI as a depth controller so that rather than it coming up once it fail-safes it should start coming back up before that happens and in theory it should run right at the edge of its range without hitting failsafe.

For leveling and heading hold I will be using a SparkFun 9DoF IMU ICM-20948 board, these are a vast improvement over the older MPU6050 and 9250 boards as it has its own onboard data processor that handles all the calculations and it will just spit out the values you need rather than raw data making integration a lot simpler since you dont need to worry about loop times or interupts messing with its calculations, you just retrieve the latest data from it.

https://learn.sparkfun.com/tutorials/sparkfun-9dof-imu-icm-20948-breakout-hookup-guide/all


for the diving system I have been looking at blood pressure collars , they look much more durable than the drip bags or balloons I have seen people use

https://www.aliexpress.com/item/1005002130699623.html

Based on recommendations I will probably go for a high capacity peristaltic pump and overvolt it to get higher performance, I will be running it from an esc so if i run it at low power for regular operation and just keep max power for emergences it should be ok.

https://www.aliexpress.com/item/32817707131.html

for propulsion im going to convert it to brushless, that video of the seawolf up out the water was too interesting for me not to try it, I belive its running something like a 500kv 3548 outrunner.

https://www.youtube.com/watch?v=GKUx1pkcV8I
Ihave ordered this 750kv motor and 60 ESC

https://www.aliexpress.com/item/1005001394664677.html
https://www.aliexpress.com/item/32769780620.html


for auxiliary propulsion im going to install a bow thruster and possibly a stern thruster if I have space and buoyancy for them, I have seen a photo of them installed in a sub and it was reported back to me that it worked really well.

https://www.theassociationofmodelsubmariners.com/t1979-water-jet-manouvering-thusters



As for a radio system , I have a 1w openlrs 458 system, frsky 868 1w sitting around, Im not sure what one il use for now.

For the video system, its not going to be deep diving, il have to keep a relatively long antenna on it above the surface as 5.8ghz will go nowhere underwater, so its just going to be used for running at periscope depth.

has anyone any other thoughts or ideas or anything im missing.? let me know

Good news! the sub arrived today and its in much better condition that i was expecting, I buy a lot of wreckage from ebay so I wasnt expecting much. its already had the bow planes connected to a servo and it looks really clean with no damage as far as i can see

geofrancis wrote:Im starting a thread there just now as i have a lot of ideas and i dont want to start new threads for all of them.




As for a radio system , I have a 1w openlrs 458 system, frsky 868 1w sitting around, Im not sure what one il use for now.

For the video system, its not going to be deep diving, il have to keep a relatively long antenna on it above the surface as 5.8ghz will go nowhere underwater, so its just going to be used for running at periscope depth.

has anyone any other thoughts or ideas or anything im missing.? let me know

given the choice of the two rf modules, i would go with the openlrs 458mhz system. considerably longer range than any of the 915/868mhz systems.


I have used the "automotive pressure sensor" myself, but be warned, there are two types of sensors, "absolute" and "differential". an absolute version is sealed, so the reading is based on the pressure from the external port versus a known vacuum, built into the unit from the factory. the differential type have two ports, one "external", one "internal". these type work by comparing the pressure differential between the two ports. it will never show a true depth based on the water pressure outside the WTC if the pressure inside the WTC is also increasing (due to a piston style or bag style ballast tank that also increases the pressure inside the WTC). if your ballast tank is completely separate from the WTC, like an OTW style ballast tank, then a differential style sensor will work.

i was able to convert a differential style sensor like you show to an absolute by sealing its internal port with epoxy, basically making its comparison value whatever the air pressure was when i glued the port shut.

lastly, i prefer the simple analog versions over the more complicated digital style because you use them with a simple analogRead() of a pin in your arduino sketch.

tsenecal wrote:

I have used the "automotive pressure sensor" myself, but be warned, there are two types of sensors, "absolute" and "differential".  an absolute version is sealed, so the reading is based on the pressure from the external port versus a known vacuum, built into the unit from the factory.  the differential type have two ports, one "external", one "internal".  these type work by comparing the pressure differential between the two ports.  it will never show a true depth based on the water pressure outside the WTC if the pressure inside the WTC is also increasing (due to a piston style or bag style ballast tank that also increases the pressure inside the WTC).  if your ballast tank is completely separate from the WTC,  like an OTW style ballast tank, then a differential style sensor will work.

i was able to convert a differential style sensor like you show to an absolute by sealing its internal port with epoxy, basically making its comparison value whatever the air pressure was when i glued the port shut.

lastly, i prefer the simple analog versions over the more complicated digital style because you use them with a simple analogRead() of a pin in your arduino sketch.

I thought this was an absolute pressor sensor as I couldnt see any vents, where are they located?

geofrancis wrote:

I thought this was an absolute pressor sensor as I couldnt see any vents, where are they located?

it is hidden somewhere in the seam between the plastic and metal portions. i wrapped the metal in painters tape to make a wall, and then filled it with 1 hour epoxy,

I have designed a new 433mhz rc system for testing, its basically a Ebyte E32 433 module connected to a Flysky Ibus serial recevier. The reason it works is the flysky protocol is one of the few that runs at a normal serial speed at uninverted levels. meaning you can just send it over any transparent serial radio thats fast enough and it should just work.

preliminary testing is showing a latency just under a second but that could still be improved, as i haven't tweaked the settings much yet.

The Ibus telemetry also runs at the same 115200 serial in the opposite direction so in theory it should have both RC and telemetry but I havent tested that yet.



In theory a system like this could be used with a relay setup where this would be either mounted on a pole next to the pond or on a boat or even aircraft in the centre of the pond or even folowing the sub, giving almost unlimited range.

Has anyone thought about making a working FPV periscope for a sub? I have been making some waterproof cameras for another project when I realized that they could be used to make an FPV periscope system. Rather than needing a tube filled with mirrors and optics, just use a small waterproof camera mounted on the end of the antenna that way the only thing above the surface will be the camera and video antenna.

to seal the cameras I have just been coating them in either epoxy or liquid insulation.








https://www.aliexpress.com/item/1005002910406092.html
https://www.aliexpress.com/item/1005003585503542.html

I have been concerned about overheating the motor in a sealed sub so I have ordered a watercooled motor mount for the 3536 outrunner motor.
https://www.aliexpress.com/item/1005005179341152.html

im waiting for parts to arrive before I can do anything else. motor, bladder and bow thruster pump have arrived but im still waiting for the ESC, pump and motor mount.