Thanks Pierre a diagram would be great. Yes wax is not to bad to remove, but you also have to make sure to keep it out of the sun, and the curcit can't have heat sinks of course, or the wax melts. I melt plastic into wax which raises the melting point to avoid the problem. --Doug J
In a message dated 6/6/2005 5:45:49 AM Central Daylight Time, poulin.carrier@videotron.ca writes:
Thanks for the many cheers guys.
Doug, very good idea with the wax/epoxy on the board. I think wax is less violent and can be removed if a small repair is needed?
The sensors are just plain copper wires put inside a 90 deg 3/8 fitting. I then filled the fitting with metal epoxy. Then I cut the wires flush (don't do that) with the end of the fitting. But I think i will redo them and leave a lent of stripped wires. The reason for that is when the wires are cut flush, water can stick to the end of the fitting and make contact forever. If the wires have a small lenght and are enough far from each other, then then water can stay between them forever.
My friend said that he is mesuring the resistance between the 2 wires. I will try to post a circuit diagram on moki later on.
Later friends!
Pierre Poulin
----- Original Message -----
Sent: Sunday, June 05, 2005 12:58 PM
Subject: Re: [PSUBS-MAILIST] BIG is now a p-sub...
Pierre
Thanks, and your English is fine. I have had problems with humidity on circuit boards before that was fixed by potting the board in epoxy or wax. You might consider it once you are sure you don't want to make any changes.
Are the sensors just bare copper wire that allows the water to complete the circuit, or is it something more complicated? What do you read from the sensor? Is it just a TTL open or closed are is there a voltage comparator? Maybe you have a circuit diagram you could share?
...and I understand that none of it is tested, very little about my boat is. :)
Thanks again
Doug J
In a message dated 6/5/2005 7:15:44 AM Central Daylight Time, poulin.carrier@videotron.ca writes:
Hi Doug, thanks.
What do the water level sensors control?
The water sensors control the air pressure inside the sub. The sensors are connected to an electronic board that then control a electric selenoid-controled pneumatic valve. That valve i letting air inside the cabine. Pressure build inside the cabine and force water out of the "sensor tube". Remember that BIG is a (almost) dry ambient sub.The pressure inside the sub is the same as the pressure at the bottom sensor. So about 1 to 1.5 psi more at the hatch inside then outside. On the surface, as soon as the hatch is closed, i have to let air in to build that 1.5 psi before I do anything else. When I open the hatch it make a big "pouf". The divers said that there was always some small bubbles leaking for the hatch and no water came in from the hatch.
Can you describe the parts between the sensors and the air tank?
As I said, sensors control an electric air valve that let out air inside cabine.
And are you using a first stage scuba regulator or something else?
I am using 2 first stage scuba regulators. I have a 5000 psi hose that connect the 2 together and one of them have a 3/8 NPT fitting in it. (my father made that modification on the regulator before I was born and for some obscure reasons...) I start a 225 psi braided hose on that fitting to the main alimentation of the sub. The regulated pressure I have is 140 psi. So the 2 scuba tanks empty at the same time. And I can't use just 1.
I'm sorry if the explanation is not so good. I have problem using english to such a very specific technical thing. I will try to take pictures of the pressure equalisation system. It will help everybody to understand. But then again, the system was not tested. Not the electric part anyway. If it works ok it will be fun because it is not very expansive to make. My friend will be glad to share the electronic blueprint also.
I hope I helped a bit :)
Pierre "looking for new ballast" Poulin
----- Original Message -----
Sent: Sunday, June 05, 2005 7:36 AM
Subject: Re: [PSUBS-MAILIST] BIG is now a p-sub...
Congratulations Pierre. A dry ambient sub for $2000 US! That is a great example for everyone that is turned away because they think it building will cost too much.
Do you have any photos of the dive?
About your air regular system you described to Silkyn. What do the water level sensors control? Can you describe the parts between the sensors and the air tank. And are you using a first stage scuba regulator or something else?
Thanks
Doug J
In a message dated 6/4/2005 10:11:28 PM Central Daylight Time, poulin.carrier@videotron.ca writes:
Hi guys,
Today we launched BIG.
After 2.5 years of design and building, moving to 4 different workshops,
investing 2500 $ (canadian, but still...) I finaly put BIG in the water!
What a trill!!!!
When it went down the boat ramp, on it's own tiny wheels, I could not
refrain myself to think that it would leak so bad, crash, explode or else.
But nothing happened. I had 2 very small leaks. Nothing a good scott-towell
could not handle.
I had 2 friends in divers outfits ready to dive so I said BIg was ready for
next step; Getting me inside it.
At first, the water-line was way lower then I though. We had to use 80
pounds of additional weight to make it as low as it was supposed to be.
So I jumped inside it, secured the hatch. Everything was still ok. I engaged
the auto ambient pressure system and... nada... The electronic circuit
didn't worked (too much humidity i think). So I had to rely on my manual
back-up to equalize pressure.
The depth where i was was 10 feet. Relaxing my breath and my hearthbeat, I
made a sign to my divers and opened the ballast vent valve. Nothing
happened. I waited for about 30 secondes and could not tell if I was going
down. I asked a diver to look if air was going out of the vent and he said
yes so i waited still longer. It tooked about 2 minutes to get the sub to go
below the water-line. What a trill!!!! oh my god! I was soooo nervous!
Looking in the top windows and seeing like 2 inches of water over the hatch!
I was finaly under-water! I made it! And was still alive!
Some seconds later I hit the bottom and rested there for a couple of minutes
ajusting the pressure, tripple checking everything. All was good. So I
decided to make BIG slightly positive. I opened up just a bit the air valve
for the ballast and I went rocket to the surface! had to wait 2 minutes to
vent the tanks, and back to the bottom I was... That time I was very gentle
with the valve and managed to get it under control. I was ready to try those
2 engines. I was very suprised how fast it was! I can easyly go faster then
a diver.
What a great day!
What was great: BIG is operationnal, it goes very fast! once you get used to
it, you can adjust bouyancy easyly. Also, very manuverable with the 2
engines set-up. more then i though it was going to be. i can almost turn on
the spot. Going up or down with motors is also very good.
What must be better: Main thing to check, It is very slow to blow the 2 back
ballast tank. I think that the holes i made are too small. Also, trim is not
good. always nose up. I also need to install propeler protection. One of my
friend fin cough in it with some minor damage to it but it is not very safe
since I plan to always use BIG with at least 1 diver.
So in all. a very good experience. What a trill! My 2 friends hang on BIG
and it was going fast. We had a wonderfull time! Even if we only been to 10
feet deep. I can't wait to put it back in the water again!
I would like to thank you all for your help in helping me realise a dream!
Special thank to Jon and Ray for making the site in the first place.
With-out you guys, BIG would still be a dream...
Thank you!
Pierre "official owner of a working p-sub" Poulin
P.S. I have a zillion pictures + video. i will post some tomorrow. Need bed
now :)
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