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Author Topic: possibilities  (Read 19031 times)

Patrick Henry

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Re: possibilities
« Reply #25 on: July 19, 2011, 09:54:33 AM »

I've just been in touch with John, and I can confirm that he is using his own test facility for this, so wildlife is safe and unharmed.

There have been instances though, of whales and dolphins suffering brain damage which has been attributed to the USN testing high power sonar in their warships, I believe off the coast of Hawaii in the deep water areas...these reports are as yet unconfirmed, as the equipment is still under wraps.
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MikeA

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Re: possibilities
« Reply #26 on: July 19, 2011, 04:12:37 PM »

How many boating lakes have you been to with whales and dolphins innit  {:- :o {-)
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Big Ada

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Re: possibilities
« Reply #27 on: July 19, 2011, 04:52:27 PM »

So we could be catching fried fish then!.

Len :-)
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Subculture

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Re: possibilities
« Reply #28 on: July 19, 2011, 07:14:40 PM »

Battered too, if you hit them!

sub john

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Re: possibilities
« Reply #29 on: July 19, 2011, 10:12:08 PM »

HI to everybody on the forum
      I have been playing about with piezo sensors on low frequencys have managed to send out real time data as what would come out of your buddy lead on your standard rc tx unit there is a few people on hear who have said that could the piezo sensors harm the pond life but if we look at pond misters that they use in ponds in gardens i think i am right in saying that they use these where there is gold fish in the pond, so it cannot be that harmfull. Problem with this is if you go to a lower frequency you don't have the band width to send fast data, every thing has to be compromise as i have said some where before you have to look out of the box some times to find the answer
             john robinson G7SCL 
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MikeA

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Re: possibilities
« Reply #30 on: July 19, 2011, 10:31:38 PM »

its all clever stuff. i was telling ur m8 if ya came up with a good solution you could market it. i found this the other day its a underwater accoustic modem i think with a range of 5km if i read correctly. i read on another forum how someone had allready come up with an idea of using it. here it is:
http://www.tritech.co.uk/products/products-micron_modem.htm

i was wonderding if this technology could be applied to model subs. i think its allready used for ROV's
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MikeA

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Re: possibilities
« Reply #31 on: July 19, 2011, 10:34:56 PM »

it transmits at 40bits per second i dont know if thats good or not.  and its 1km not 5 lol
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Subculture

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Re: possibilities
« Reply #32 on: July 19, 2011, 11:28:58 PM »

That's very slow. No way you could use standard PPM with that data rate.

I was thinking along the lines of 160 bits per second (two bytes of data sent every 100ms) using infra-red commands instead of ppm signals.

Getting my head around CRC checks, and how to implment that in BASIC in a Picaxe processor.

MikeA

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Re: possibilities
« Reply #33 on: July 20, 2011, 08:42:35 AM »

 can each command be sent by different tone? then could the servo positioning rate be sent via pulses? like the faster forward you want to go the faster the pulses are sent down in the water and then the faster the sub?
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dreadnought72

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Re: possibilities
« Reply #34 on: July 20, 2011, 10:43:29 AM »

I was thinking along the lines of 160 bits per second (two bytes of data sent every 100ms) using infra-red commands instead of ppm signals.

Getting my head around CRC checks, and how to implment that in BASIC in a Picaxe processor.

Isn't that a bit overkill?

Given the limit on the amount of data sent, might this be a better approach...

1/ Send a single digit parity bit per burst, just to check the general validity of the data. Easy

2/ On the sub, disregard that burst if the bit doesn't match. Easy

3/ If the bit does match, use the Picaxe to compare the current status of a servo/esc (however you encode it) with the newly sent value.

4/ If the difference is less than X%, assume the new value is true. You're moving the sticks a little

5/ If the difference is greater than X%, store the new value and check this against a future value. You've moved the sticks a lot, and this allows confirmation of the move

6/ If the next values match (within X%) of the "suspicious" value, assume this command is true.

Andy
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Patrick Henry

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Re: possibilities
« Reply #35 on: July 20, 2011, 02:27:55 PM »

I'd put the Pickaxe right through the whole lot...
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sub john

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Re: possibilities
« Reply #36 on: July 20, 2011, 07:48:08 PM »

HI Mad Mike
 In reply to#30 you said that there could be a market for this the idea is Mike that if you could build a system for low frequency what ever it is and be able to use your standard transmitter that you are using now 27MHz or 40MHz or even 2.4Hz DC7 if you can use the buddy lead on TX to use code to transmit data to low frequency link to sub it starts to get cost effective because you already have a transmitter. Other point i would like to bring up is because most of you have aerials on your TX unit it is not the way to get through the water, because most of your looses happen when the signal from the aerial skips off the surfaces of the water like skipping a pebble across the water, but if you was to put your antennae in the water from TX transmitter now its a hole new ball game as i have been playing about with again with aerials which transmit but are in the water, a full wave aerial would be in air 33feet long at 27MHz but if aerial was put in the water it would become many times smaller and what you can do is put aerial on a float point vertical downwards other point is because of aerials becoming smaller in water your Rx aerial in your sub is completely out of tune on the front end of Rx unit but what you can do is make front end on Rx auto tune it self, and again this can be made to work because i have done it but some of these things have taken a long time to work out
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Subculture

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Re: possibilities
« Reply #37 on: July 20, 2011, 07:55:51 PM »

Is the smaller aerial owing to waters greater density than air?

sub john

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Re: possibilities
« Reply #38 on: July 20, 2011, 08:06:20 PM »

Hi subculture #37
      Yes it is but it does change worst case salt water, swimming pool next, the normal pond water just to give you some idear of size of Aeriel in air at 1.8MHZ would be 167meters long which is a big Ariel which is a full wave but in water it would be about 10.1meters as you can see it is a lot smaller it does get interesting
             John G7SCL
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admiral donuts

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Re: possibilities
« Reply #39 on: July 20, 2011, 08:33:49 PM »

I have been told (unofficially)that Stepen Hawkings is looking into this topic with a view to using the technology in his exploration of black holes and neutron stars,as for me I think I will stick to Futaba and a short aerial.No dead fish and no worries about lightening bolts with that long mast in the air

Just kidding guys

A very confused Donuts
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Patrick Henry

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Re: possibilities
« Reply #40 on: July 20, 2011, 08:50:46 PM »

You're confused, Donuts? I haven't had a clue what they have been talking about all the way through!
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roedj

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Re: possibilities
« Reply #41 on: July 20, 2011, 09:43:19 PM »

Hi subculture #37
      Yes it is but it does change worst case salt water, swimming pool next, the normal pond water just to give you some idear of size of Aeriel in air at 1.8MHZ would be 167meters long which is a big Ariel which is a full wave but in water it would be about 10.1meters as you can see it is a lot smaller it does get interesting
             John G7SCL

The word that covers all of this is 'velocity factor'. All of these great formulas for calculating the lengths of antennas are only valid in a vacuum - speed of light and all that. When you're talking about any other medium - water, for instance - the speed of light or any other electromagnetic radiation, i.e., our radio waves, slows way down. I always get a private chuckle over all these people who worry about the length of the antenna in their sub when once they put it in water all the calculations go out the window.

Over the years I've read many different ideas on how to communicate with model subs under water by sound waves. I've yet to see one work. In almost all cases it's the slow data rate that foils them.

Best of luck with your endeavors,

Dan K8XW
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Patrick Henry

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Re: possibilities
« Reply #42 on: July 20, 2011, 10:27:22 PM »

So does that mean that rx aerial length isn't important in a sub?
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MikeA

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Re: possibilities
« Reply #43 on: July 20, 2011, 10:50:32 PM »

its great to see such an interest and the people who have the ability to comprehend a method of my ''what if imagination''. I have no idea half the time what your even talkin about ive only just got my head around what amps in relation to voltage is lol. if you were to need such a long antenna couldnt if be done with a coil of wire? it doesnt need to stick up in the air does it.  The point is john that if you were to produce a successful and practical system to install in subs people would be interested. Even if it is currently an expensive thing to do. People with deep pockets are more than willing to fork out 5k on a jet engine and 1500 quid on an fpv system for planes, im sure there are sub builders who would like to be able to go 100 ft out 100ft down with there sub, and sum people would be more than willing to remortgage there house to do so. cheapness comes with development. And by that point china will have got hold of it and theyll be selling them on ebay for ten a penny.

do you have a functional system yet?
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roedj

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Re: possibilities
« Reply #44 on: July 20, 2011, 11:16:13 PM »

So does that mean that rx aerial length isn't important in a sub?

Beyond there being a necessity for 'something' of an antenna to sense the signal, pretty much - no.

All of these finely tuned antenna lengths are OK for planes and surface vehicles where the antenna is out in the air (more or less) because in that case the speed of light is close to that of the speed in a vacuum. That being the case, the length as determined by the receiver manufacturer is 'sorta' important. But put that sucka under water - you're on your own, Sport.

Regards,

Dan
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Subculture

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Re: possibilities
« Reply #45 on: July 21, 2011, 03:22:27 AM »

This is all very interesting dialogue. Apologies if it's cooking some folks amino acids, but it makes a refreshing change from discussing hacking at fibreglass etc.

Commericalising a system like this is a tall order indeed. I'm thinking along the lines of starting very simple at first, maybe try it out on something extremely basic like making an LED flash in different ways depending on the command sent, and sending this data using audible frequencies.
That should give me a good idea of range, and whether the signal suffers from corruption etc.

For what I had in mind I don't really require the frequency rate of normal R/C, and wasn't intending on using the conventional gimballed sticks, instead I was looking at dedicated buttons like a TV remote. I was considering the use of piezo transducers as an 'aerial' attached to hull of the boat, so it acts like a large sonar array to pick up the sound signals.

MikeA

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Re: possibilities
« Reply #46 on: July 21, 2011, 09:53:26 AM »

one of the features of that modem i put up was the fact it isolate and home in on the signal and cancel out the unwanted crap. like fish noises and echo etc. Even if the sub was controlled by ''hydrophonic tranmission'' you still need a live visual feed back. which in the end i feel is the Achilles heel. dont know how you would do that mind  %%
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MikeA

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Re: possibilities
« Reply #47 on: July 21, 2011, 10:08:51 AM »

i dont understand the thing with the lenght or aerials. is john saying that on a typical open air anntenna it has to be 180meters long but if you put it in water it only has to be 10 metres long  :o
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sub john

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Re: possibilities
« Reply #48 on: July 21, 2011, 11:02:42 AM »

HI MAD MIKE

yes anntena in water is 10.1 metres long at 1.8 mhz yes i have a functonal systtem on LF band ppm data

JOHN G7SCL
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MikeA

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Re: possibilities
« Reply #49 on: July 21, 2011, 02:38:03 PM »

got any youtube footage  :}

cheers
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