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by perfo
Fri Jan 23, 2015 7:49 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

I should start another thread really as this has gone way out of the hdmi to laser area. My latest idea is something completely different. As I can't have a tether to the cameras I'm thinking of a drone instead. I didn't go up the path of using a ROV to mount the camera on due to it needing a skille...
by perfo
Wed Jan 21, 2015 1:26 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

ha yep... The carrier may be a simple sine wave or something but I agree there could be nothing else simple about it... I shall continue my search for knowledge on it...
by perfo
Wed Jan 21, 2015 9:54 am
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Good idea, I have done a little search to see if anyone has done exactly that..but can't seem to find any. Does this mean it's not easy to do ? I thought (as you did) it will be a simple carrier sent to a transducer and if so it should be able to be modulated. They do appear to be a little sensitive...
by perfo
Tue Jan 20, 2015 11:23 am
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Interesting read, I shall probably have to read it several times before fully understanding it :) It does seem to prove (not theoretically suggest) that 10's cm are possible with 2.4ghz... So all I need to do it to come up with a wave guide to get that signal to the surface and I'm on to a winner. I...
by perfo
Tue Jan 20, 2015 10:05 am
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

PIGraham, if you scroll down in the doc I sent you'll see they also do calculations for 2.4Ghz and state for average fresh water the theoretical penetration depth is just over 16cm which maybe enough for me... I haven't got access to many 5Ghz gear but borrowed some and then threw them in a lake :) ...
by perfo
Mon Jan 19, 2015 8:56 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Some interesting stuff, I’ve been digging in to the physics of it all just to try and get my noggin around what the problems with Wifi and frequency are ( I didn’t manage). However after a bit of research I came across a paper calculating the penetration depth of electromagnetic waves in water. If u...
by perfo
Sat Jan 17, 2015 12:13 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

I've been chatting to a fellow that can supply a leaky feeder for 30m . Again it would have have to be tested to see if the coax can survive in 30m depth due to it containing air voids in it's structure. But the losses over 30m of Leaky feeder antennae isn't fantastic so as long as I can aim the Yag...
by perfo
Sat Jan 17, 2015 10:49 am
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

The 15 cm mentioned in the paper is also in salt water which I'm guessing is a worse medium than fresh water it does look promising. There are a minimum of four places in the pit on each side where i'd need to see the latches. So if I were to have AP's under water then I'd need eight per pit , unles...
by perfo
Fri Jan 16, 2015 5:12 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

just trolling the eBay I can get a Yagi 25dbi antennae (item 251370446239) for £5.00 I would have to mount this in a pipe or something to keep it in air I guess.. I can also get a 2000mW USB WiFi adapter for £9 (item 151460450701) .... Could any clever fellow assist me in working out what difference...
by perfo
Fri Jan 16, 2015 4:59 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

As I'm back to WiFi I'm going to try another experiment. I'm going to put a bit of cable inside a pipe (as explained before) this cable wouldn't be connected to anything it will simply be floating (electrically speaking. Putting it inside a pipe will keep it dry and thus not earthed by the water. A ...
by perfo
Fri Jan 16, 2015 4:53 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Just one last suggestion for now. Forget about the Pi and find something that is capable of transmitting a video signal underwater. Like this: http://www.japantrendshop.com/rc-12-wireless-mini-waterproof-video-camera-p-225.html I've just had the reply about this item and unfortunately they state it...
by perfo
Thu Jan 15, 2015 9:24 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Since you know a tether will be broken eventually you can account for that by using a sacrificial tether. Something as simple as a waterproof RJ45 connector on the camera and a 30m ethernet patch lead. Every time the patch lead gets torn or chopped, clip another one in. It simply becomes a consumab...
by perfo
Thu Jan 15, 2015 9:21 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

I think it will be easier to devise a reliable latch & sensor to confirm the latch is good than to feed images wirelessly from 30m underwater. Does the beam travel with the crane? Is this one beam that is lowered in every case? Can't you run cable down from the beam to the hook? Sounds like a job f...
by perfo
Thu Jan 15, 2015 9:10 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Just a thought: what you are interested in isn't the camera output but whether or not the latches have engaged. Could you use an optical recognition pattern to identify the latch engagement, then send you a single jpg as confirmation? Yes indeed that could be an option..a smart idea ,, thanks.. As ...
by perfo
Thu Jan 15, 2015 9:08 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Couple of quick remarks: 1) You may find Ronja, optical point-to-point data link interesting, see http://ronja.twibright.com/ for details. 2) LEDs can be pulsed fairly fast (FWHM down to ~10ns) with reasonable efforts, the power in single pulses is not very high. As you seem to have the possibility...
by perfo
Thu Jan 15, 2015 6:15 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Just one last suggestion for now. Forget about the Pi and find something that is capable of transmitting a video signal underwater. Like this: http://www.japantrendshop.com/rc-12-wireless-mini-waterproof-video-camera-p-225.html wow. Its not clear form the description if this will actually transmit ...
by perfo
Thu Jan 15, 2015 6:13 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Is the pole hollow? Can you run a cable down the pole? Can you run a cable behind the pole, where it is away from the beam and screens? If the pole is hollow, can you put the camera inside? Why can't you attach cameras to the beam and run the cable up alongside the crane cable? No more ideas for no...
by perfo
Wed Jan 14, 2015 5:28 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

yep all understandable comments thanks Back to WiFi for a minute then as the optical thing seems tricky. Ah something I forgot , when I said I got about 5 cm in my first low power normal WiFi tests I meant I could transmit data from one device to another over 5cm gap in the water the signal may have...
by perfo
Wed Jan 14, 2015 4:46 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

what data are you wanting to send ? HDMI is never going to work and why are teathers not usable , how is the RPi powered , Pictures from the PI cam even 1 FPS would be ok and doesn't have to be full HD a 640 X 320 would be ok... It is difficult to explain why tethers and such wont be practical. but...
by perfo
Wed Jan 14, 2015 4:40 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

are you suggesting that lasers or LEDs just wouldn't go fast enough? Is it not just a driver circuit stuck on the TX cable of the Ethernet port ? The experiments that a colleague and I conducted showed that we weren't able to switch high power LEDs fast enough to send data at a decent rate. Lower p...
by perfo
Wed Jan 14, 2015 4:01 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Is it possible to have loads of parallel circuits with ultra sound? Multiple RX TX pairs with slightly different frequency. I don't know what frequency separation they'd need but I guess the big downside would be the waves will interfere with each other and reflect compound / destroy etc etc...
by perfo
Wed Jan 14, 2015 3:54 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

thanks for your comments gent, Yep ultra sound does work and works well but far too slow to give any sort of decent live pictures. even if I only send one pic at a time it still takes tooo long for any sort of resolution but I did try it to see if I could communicate over the 30m and I could fairly ...
by perfo
Wed Jan 14, 2015 12:14 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

The transmitter will be under water at 30m deep , the receiver can be underwater or out of water. Interesting links you gave me PiGraham I have been searching the net and have give those a read. I was particularly interested in the network over white LEDs and this is the kind of thing I'm thinking m...
by perfo
Tue Jan 13, 2015 9:45 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Sorry I forgot to mention I did look at boys tethered to the rpi thing but it wouldn't really work. I could do an auto paying out/ reeling in thing on the body but it's not ideal.
by perfo
Tue Jan 13, 2015 9:42 pm
Forum: Other projects
Topic: HDMI to laser
Replies: 49
Views: 5239

Re: HDMI to laser

Thanks for the reply. I manged to get up to 5cm with 2.4ghz and not quite doubled this with special antennae and as much power as I could get out of a high power WiFi. So I was disappointed but it became clear I was never going to get WiFi to work over this distance. If anyone could help me with a c...

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