Electronics on towfish

[bob]

Something to think about... Patrick's fish is very straightfoward (hence it is the first to make it into the water!!) but when we put electronics on board, things get more complicated..


I figure if we want to have a maximum depth of 300 ft, (100m) the water pressure will be about 150 psi. (sorry, don't know the metric equivalent!)


Has anyone thought about the design of a watertight compartment to hold the electronics? It would be good to think about the size of this before deciding on PCB sizes!

[Sture Hultqvist]

Re: Electronics on towfish

Hi


I did my housing in stainless steel tube 100 x 2 mm


and so far it have been on a maximum depth of


70 meters. Sorry about the metric values.


I have not done any calculations about this but


I think it could stand lot more.


Sture

[Jan]

Re: Electronics on towfish

Bob,


For me 100 meters is to deep.


Cannot dive that deep without Trimix and several hours deco.


I was planning on max 50 meters.


My fish will be rectengular shaped.


Size will be about 150x25x25 cm, which is very large.


I want the space for testing. Working with cramped spaces is to much for my otherwise friendly nature


It will be very difficult to determine fish size at present, we do not know what is going in there yet.


That is why my fish is so large...


Just as indication I could think of next parts that must fit in it:


1) Battery 12V/7Ah


2) 2x transducer array


3) PCB (+/- 6x9") transducer control


4) PCB (+/- 6x9") communication + Fish data (like depth sensing)


5) PCB (+/- 6x9") High voltage + power control.


This is assuming you do not want any depth control.


Hope this gives some indication.


Regards, Jan

[bob]

Re: Electronics on towfish

Sture,


How do you keep the water out, and yet still allow access to the electronics? Do you have a screw top or someting?


Also, if the tube is filled with air, doesn't it float?


Thanks,


-Bob

[bob]

Re: Electronics on towfish

I dobut that I'd go that deep either, but it wouldn't hurt to design it to go down that far.


Plus, I have some crazy friends that do go down that far! (Don't ask me!) There are a lot of wrecks between 70 and 100 meters here on the US East Coast. Personally, I'd be happy watching the scanner from the surface!


Regardless of size, I figure it is pretty easy to test.. Just throw it over the side in deep water and see if it comes up dry!


-Bob

[Jan]

Re: Electronics on towfish

Bob,


You are right about water test, but I meant testing of electronics.


I hate it when I cannot put scope probes etc on.


I expect that first design will have many problems, so electronics must be reached easy.


Later, when all works and I know what goes in, I might build smaller one.




Regards, Jan

[Jan]

Re: Electronics on towfish

Bob,


You are right about water test, but I meant testing of electronics.


I hate it when I cannot put scope probes etc on.


I expect that first design will have many problems, so electronics must be reached easy.


Later, when all works, I might build smaller one.




Regards, Jan

[Patrick]

Re: Electronics on towfish

Deep is good. I'd like to be able to identify wrecks up to the 350' range.


Sture,


How long is your cable?


What is the max depth you have identified wrecks with the cable out all the way?


What is the max depth are you able to identify wrecks with your SSS? Is the lmitation the "fish", the cable, or the power?


Thanks,


Patrick

[Patrick]

Re: Electronics on towfish

Jan,


Am I reading this correctly ... you are planning on putting boards in the fish that are 6"x9"?


If this is true, the fish would have to weigh quite a bit to get it negative in the water.


Patrick

[Jan]

Re: Electronics on towfish

Patrick,


The boards are what we call Euro format here.


They are about that size.


My fish will be flooded for half its length (but still needs to weighted)


Regards, Jan

[Patrick]

Re: Electronics on towfish

Jan,


How big do you estimate the "fish" is going to be when complete?


Patrick

[Jan]

Re: Electronics on towfish

Patrick,


No idea yet.


Depends very much on how much I can get into the software.


The 3 cards I mentioned before is what I etimated as maximum.


At the moment I am thinking over several ideas, and it looks like I might get the software to take over most of the hardware.


This would be good because I can then change, adjust, redesign without much hardware redesigning.


But have to wait until I get the program I ordered and do some timing tests on actual PIC's


All this might overload the PIC a bit, so I have to do multiplexing. (let several PIC's alternately do some work)


Sorry for the long reply with no answer to your question.


Regards, Jan

[Sture Hultqvist]

Re: Electronics on towfish

Bob


The rear part with the fins is removable and


sealed with a O-ring. This allows me to work


with all parts in place. In fact I can remove


the front part also and put the transducers on


a table for testing.


It is clerly visiably on my homepage.


The current building (wich I not have written


about so far) will be a tube with a cover in


the tail and will be less friendly to service


but easier and cheaper to build. The size will


also be smaller with 800x70x2 mm stainless tube.


(the other is 1400x100x2mm)


The weight I still not know, I guess 10Kg


compared to 25Kg for the user friendly one.


None of them float...


For upcoming project in mountin lakes I need


a smaller unit operatable from small rubber boats.


And also the "MyggA" against mosquitos......


Sture