Looking for an underwater ranging device

[Alois LUONG]

Hi guys,

I am working on a project: an underwater camera that follows a swimmer from under to film him. I am doing so by having a robot move up and down on a wire using motors and an arduino board. I want this robot to move at the same speed as the swimmer. Therefore, I need to find a way to measure the distance between the robot and the swimmer in order to adjust the speed of the motor.

I was wondering if there are 2 device (1 on the robot and 1 attached on the swimmer) that can measure the distance between each other and send it to the arduino board.

In summary, I am looking for a device that can:
- work underwater
- measure the distance between the robot and swimmer (can be a 2 piece device, 1 on the swimmer and 1 on the robot)
- can output this distance to an arduino board
- be in a student's budget (so nothing above $100)

 

[Externet]

Unclear... move up Δ and down ∇... do you mean instead, along the swimmer direction forth and back ↔ ?
The video camera 'on-a-cable-car' to grab onto the wire for wheeled propulsion or just for guidance using propellers ?

The distance measurement can be the same equipment as in ultrasonics distance measurements on air, waterproofed. Interfacing to Arduino, I do not know. ----> https://www.aliexpress.com/wholesale?SearchText=ultrasonic+distance+measurement&opensearch=true

Waterproofing motor shafts is not simple, prepare for frustrating tests.
Very hard to accomplish if you do not have a pool very nearby at nearly all times.
Have you investigated if you will be allowed to anchor the 'wire' to a pool walls/bottom ?

Highly doubt that budget will do it. Rental of scuba equipment will eat a good chunk of it.

----> https://donaldmiralle.wordpress.com...erwater-cameras-at-rio-2016-olympic-aquatics/

----> http://www.nytimes.com/2012/08/01/s...otographers-make-their-underwater-moment.html

----> http://money.cnn.com/2016/08/08/technology/olympics-underwater-robots-getty/index.html

----> http://www.poolview.co.uk/swimpro-cam

 

[Hopup]

Pretty much impossible to make it with that budget, maybe if you can do it very simple way, traveling bottom of the pool, it would be possible.

If it needs to be submarine style construction it will be quite hard to do and certainly not with that budget.

 

[kellys_eye]

Tie the camera to the swimmer.

 

[Externet]

...To the swimmer belly button and lay mirrors at the bottom of pool...

 

[Alois LUONG]

Pretty much impossible to make it with that budget, maybe if you can do it very simple way, traveling bottom of the pool, it would be possible.

If it needs to be submarine style construction it will be quite hard to do and certainly not with that budget.

Hi,

Just to clarify, the $100 budget was only for the measuring device.

Best

 

[Alois LUONG]

Unclear... move up Δ and down ∇... do you mean instead, along the swimmer direction forth and back ↔ ?
The video camera 'on-a-cable-car' to grab onto the wire for wheeled propulsion or just for guidance using propellers ?

The distance measurement can be the same equipment as in ultrasonics distance measurements on air, waterproofed. Interfacing to Arduino, I do not know. ----> https://www.aliexpress.com/wholesale?SearchText=ultrasonic+distance+measurement&opensearch=true

Waterproofing motor shafts is not simple, prepare for frustrating tests.
Very hard to accomplish if you do not have a pool very nearby at nearly all times.
Have you investigated if you will be allowed to anchor the 'wire' to a pool walls/bottom ?

Highly doubt that budget will do it. Rental of scuba equipment will eat a good chunk of it.

----> https://donaldmiralle.wordpress.com...erwater-cameras-at-rio-2016-olympic-aquatics/

----> http://www.nytimes.com/2012/08/01/s...otographers-make-their-underwater-moment.html

----> http://money.cnn.com/2016/08/08/technology/olympics-underwater-robots-getty/index.html

----> http://www.poolview.co.uk/swimpro-cam

Hi,

Thank you for your quick response! Just to clarify, the $100 budget was only for the measuring device. Instead of using an ultrasonic device (which would be hard to program), I was thinking of a 2 part device (mounted on both the swimmer and robot) that measure the distance between each other and output it. An example of this would be: https://www.nanotronshop.com/nanoloc-ranging-kit-ii-p-17527.html ,however, this is way out of my budget and doesn't work underwater.
The link you have are interesting but they cameras are only for photography, not filming (which is what I am looking for). I am trying to develop my own system instead of buying a professional one used in the olympics

For the rest, I have solutions for:
- I will use a waterproof brushless motor to move the robot
- the cables will be tied at both ends of the pool using special suction cups.
And yes, when I mentioned about UP and DOWN, I meant going up and down the pool lane. I also live in a house with a pool.

Best

 

[Externet]

The 'cable rail car' can house a movie camera instead of a photo camera...
The first link includes laser ranging gadgets, not only ultrasonics, near your budget...
The brushed or not condition for the motor does not change the need to waterproof shaft/bushings.

Out of the box... Explore if the motion can be instead, following the shade of the swimmer projected at the bottom of pool. Tricky, but a directional (lensed) light sensor on the cable car could command the motor.
Out of the box... a LED, infrared or not on the belly button/trunks could be traced by the camera with some imaging following software to command the cable rail car motion... Until the swimmer does his thing belly up

And up and down is then definitively wrong, that would be surfacing/sinking. It is forward and backward.
The wrong habit of saying going 'down the street' even when you are returning is not 'up the street' does not apply here.

Edited: The mindset "measure the distance" could be replaced by a 'follow' the swimmer.
---->

 

[Nanren888]

Sorry, not clear on how ranging gets you what you want. If I see the range increase, how do I know whether I am going too fast & getting ahead or too slow & falling behind?
Bistatic ranging, sending from one & receiving on the other requires some sort of synch between them to know when the transmission was. Transponders have different issues.
I guess if you're allowed cables, the drives can be above water & only the minimum electronics below.
If all costs of packaging & testing are aside, that is parts costs alone (from aliexpress), and development costs are all free student time, you might almost do it, maybe, if you can find cheap transducers & aren't going to want to have lots of these things in the pool at the same time. (After all the ranging example you gave was only 800 Euros.) There was mention on this site of cheap ultrasonic cleaning transducers, but I don't now the specs.
Reverb is a problem in pools. The floor & surface will both be reflective.

 

[FuZZ1L0G1C]

If you can get away with a long, thin, clear-insulated flexible wire, almost invisible under water, maybe you could use one probe on the swimmer, the other on the camera housing.
As tap water has a DC resistance of about 400K-600KΩ/m, 'poolarised' water may be slighty lower due to salts and other chemicals.
As the swimmer departs, resistance (low voltage DC) increases with distance, and an interface could speed up the drive motor until resistance falls to set threshold.
Just don't pee in the pool - otherwise camera will slow down or stop.
EDIT: While testing H20 Ω/m using a DMM on auto-ranging, I noticed that resistance hunts all over the place, so some form of time-averaging the R reading would be needed, to avoid jerky camera movements.

 

[FuZZ1L0G1C]

Another idea:
As sensing the swimmer's position via shadow / ultrasonic / resistance may be hit and miss, the robotic camera should ideally be controlled manually, either directly (get out that scuba gear), or remotely via long interface cable & small poolside monitor.
I'm thinking along the lines of waterproofed Go-Pro & Smartphone.