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Does anyone have a working speed sensor?

R/C Submarine modelers

Does anyone have a working speed sensor?

Postby Ramius-II » Tue May 01, 2012 9:26 pm

Hi All, :D
I have been away for a while and at one point in time there were some research being done on being able to tell how fast our subs are traveling in the water or under the water. Has anyone solved this yet? There were some ideas such as a "paddle wheel" and pressure sensors. Thanks, Ed! :D
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Re: Does anyone have a working speed sensor?

Postby salmon » Wed May 02, 2012 2:14 am

Ramius,
Welcome back! Glad to see you post!
How is the Typhoon?
Peace,
Tom
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Re: Does anyone have a working speed sensor?

Postby Ramius-II » Wed May 02, 2012 7:11 am

Hi Salmon!
Thank you! The Typhoon is good thanks, just finished the depth sensor which was a lot more complicated and more difficult than I first imagined. The actual sensor is an Intersema MS-5541C .375" in diameter and about .125" high. It can resolve 0.5 inches. Now it's time to look at the last sensor which is speed.

Best, Ed
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Re: Does anyone have a working speed sensor?

Postby salmon » Wed May 02, 2012 1:09 pm

The speed sensor, I assume you want internally and not attached externally like this? http://www.instructables.com/id/Turbine-Flowmeter/?ALLSTEPS
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Re: Does anyone have a working speed sensor?

Postby Ramius-II » Wed May 02, 2012 3:46 pm

Yes, internally would be wonderful!
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Re: Does anyone have a working speed sensor?

Postby StuartL » Thu May 03, 2012 2:20 pm

I've heard of ultrasonic speed sensors being used which time the pulse from transmitter to receiver and use the difference between the expected delay (proportional to the distance between them) and the actual delay (the result of which is proportional to the speed) to determine the speed.

I've no idea on accuracy of such a method, I suspect it's quite accurate but have no first hand experience.
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Re: Does anyone have a working speed sensor?

Postby Sub culture » Thu May 03, 2012 4:07 pm

Eagle tree use a pressure sensor and pilot tube. Have a look here-http://www.eagletreesystems.com/Boat/boat.html
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Re: Does anyone have a working speed sensor?

Postby Ramius-II » Thu May 03, 2012 4:42 pm

Thanks guys!
Yes I am familar with the Eagletree pitot tube. The questions would be how much pressure, and more importantly how would you mount it in a Typhoon? Eagletree says the tube must stick out in front and is designed for speed boats.

Best, Ed
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Re: Does anyone have a working speed sensor?

Postby Sub culture » Fri May 04, 2012 5:39 am

I would think stick it under the hull, but not on the nose (area of high pressure). Would require some experiementation. I've used Eagletree loggers for about three years now in model aeroplanes, the pseed sensor works great. Only used RPM volts and amps in boats/subs though.

Why not have a word with Eagletree, I've found them very helpful in the past.
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Re: Does anyone have a working speed sensor?

Postby Ramius-II » Fri May 04, 2012 8:01 am

Thanks Sub Culture!
I did have "speaks" with Eagletree some years back and they were not certain it would work. Typically the Pitot tube has to be free of any flow disturbances which is why they mount the tube in front of the wing on airplanes. Just to give you a smile, some of the airplane guys have mounted the sensor almost behind the airplanes prop which gives a much higher indicated air speed! If I understand the physics involved, speed is a function of incomming pressure on a sensor compared to static pressure? It would seem to me that if you have your depth sensor in an area where there is no "flow" (static water pressure) and then compare this to incomming pressure you should be able to calculate the speed? Again I do not know enough about fluid flow characteristics. I did build a "venturi" type sensor however there did not seem to be enough pressure to get any readings. At http://www.flowmeters.com/ they show various types of flow meters. Maybe my research abilties with Google are not very good as I would think with all the RC speed boats someone would have built a speed sensor? I very much appreciate being able to discuss this with all the wonderful people here.

Best, Ed
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Re: Does anyone have a working speed sensor?

Postby Sub culture » Fri May 04, 2012 8:39 am

One of the most knowledgable people I've seen on sensing parameters on a model submarine is John Robinson, he posts quite a lot over on Model boat Mayhem, have a look at his 12 foot Gato post in the submarine section to see what he has done with that behemoth.

http://www.modelboatmayhem.co.uk/forum/ ... ic=32161.0



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Re: Does anyone have a working speed sensor?

Postby salmon » Fri May 04, 2012 2:37 pm

Ed,
That is a good tip from sub culture, John's electronics are very impressive. I think you are the trail blazer on this one! To go where no submariner has gone before....
May the Fourth be with you!
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Re: Does anyone have a working speed sensor?

Postby Sub culture » Fri May 04, 2012 5:08 pm

Another possibility was to mount an axial blade e.g. a propeller, free running hooked up to a magentic encoder- count the revolutions. Bound to have quite a lot of slip, not to mention non-linearity, so would need calibrating and probably linking to a map/control table.
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Re: Does anyone have a working speed sensor?

Postby Ramius-II » Fri May 04, 2012 5:38 pm

Yes and it seems most people are using a "paddle wheel" system. The "fun" part is that just when you think you have found a solution such as the information contained in Maxim app note AN-884, you find that all you wind up with is the "theory" and no real hardware! It certainly is a "challenge" :o Best, Ed
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Re: Does anyone have a working speed sensor?

Postby Scott T » Fri May 04, 2012 6:15 pm

What about one of the sports device that tracks your mileage and route for runners. Maybe it also logs
running speed. If it does calculate speed it would have to be checked to see if it operated submerged in
water. Or maybe make a cell phone app that tracks location and speed. I read somewhere that the traffic
flow speed reports they show on the news are the cell phone towers indicating the cell phones moving up and down
the highway trying to get a signal from the cell towers. Then your phone could do double duty if works
submerged.

Scott T

edit Did anybody watch where they sent the I-phone up on a ballon? It videoed and logged the route with GPS.
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