[PSUBS-MAILIST] Mechanical Depth Gauges

Mon Jul 30 19:16:46 EDT 2018

Doug,
arduino is the big thing in hobby electronics. It's a tiny computer board
that is designed to interact with the environment. Ie. you might have various 
sensors like pressure, motion, light, or a switch etc that send a signal into the 
arduino & the arduino outputs some action depending on the program you
write & the outputs you add to it. It is used a lot in robotics. The programming 
language is reasonably simple & designed for beginners & hobbyists. 
My local electronics store has a couple of stands full of sensors etc for it. 
There are a number of arduino boards, uno, mega, duo etc.
It is like the raspberry pi but not as powerful. There are other more powerful
boards than raspberry pi on the market.
   If you bought a pressure sensor with a 4-20ma or 0-5V output you could
wire it to the arduino board & calibrate that signal into a depth range that is
outputed to an led screen, and also sets off an alarm at a certain depth.
There are good on line courses on it on UDEMY. 
I was going to buy a plc ( industrial computer) but are now going to do 
everything with arduino, raspberry pi etc. 
Jon, Cliff & others are a lot more competent than I am with this, so there
would be plenty of help if you wanted to go that route.
Alan

Sent from my iPad

> On 31/07/2018, at 9:56 AM, Douglas Suhr via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Ah, I think that would be great (to oil compensate the gauge).
> 
> It would be very cool to have a digital display that could be switched
> from fresh to salt water. And though you are correct that I am young
> Alan, I'm not too tech savvy. I've never even heard of Arduino before
> - is that like Raspberry pie? 'Cause I've heard of this pie computer
> and all I can think is, 'Yeah, I'll take a slice with some vanilla ice
> cream please.' :) ~ Doug
> 
> On 7/30/18, Alan via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>> Doug,
>> I am not sure how Snoopy's pressure gauge is set up but
>> I know of at least one person that has a rubber solder sucker filled
>> with oil screwed ( or attached) to the outside of the gauge port.
>> The gauge then only sees oil not sea water.
>> Gauges with electronic displays & the ability to flick between metric,
>> imperial, psi, mpa etc are pretty cheap. I have a dwyer gauge ( somewhere).
>>   Being a young person you may want to go down the route of buying
>> a gauge that you can attach to an arduino, then electronically display on a
>> 
>> board as big as you like! With a bit of code at the push of a button you
>> could get it to display fresh or salt water depth.
>> Cheers Alan
>> 
>> 
>> 
>> Sent from my iPad
>> 
>>> On 31/07/2018, at 6:36 AM, Douglas Suhr via Personal_Submersibles
>>> <personal_submersibles at psubs.org> wrote:
>>> 
>>> Ah, I think you're right Jon... because the gauge plate would not be
>>> pressured anyway, huh. Never thought of that.
>>> 
>>> No there was no gasket or anything, so I guess any moisture in the
>>> viewing portion of the gauge would just come from moisture inside the
>>> hull of the sub.
>>> 
>>> And thank you for the pressures... not a huge difference but I suppose
>>> at deep depths it could work out to be somewhat of an error.
>>> 
>>> I wonder how Alec printed such a nice looking label(?). ~ Doug
>>> 
>>> On 7/30/18, Jon Wallace via Personal_Submersibles
>>> <personal_submersibles at psubs.org> wrote:
>>>> Fresh water: .433psi per footSalt water: .445 psi per foot
>>>> If there was no gasket sealing the acrylic/glass cover and bezel then
>>>> it's
>>>> likely condensation caused the wrinkling of the label.
>>>> Jon
>>>> 
>>>>     From: Douglas Suhr via Personal_Submersibles
>>>> <personal_submersibles at psubs.org>
>>>> To: Personal Submersibles General Discussion
>>>> <personal_submersibles at psubs.org>
>>>> Sent: Monday, July 30, 2018 1:16 PM
>>>> Subject: [PSUBS-MAILIST] Mechanical Depth Gauges
>>>> 
>>>> All, as you may've been aware, in late 2015 I purchased Snoopy (a
>>>> K-250) from Alec Smyth. Regrettably I have been quite neglectful of
>>>> performing much upkeep on the sub, save for keeping the batteries
>>>> topped off. My schedule is finally allowing me to spend some real time
>>>> working on the sub and getting to know the specifics of each system.
>>>> 
>>>> As you can imagine, I've been bugging Alec with a question here and
>>>> there, but thought with this topic I should start a discussion here on
>>>> the list for the benefit of anyone else who might have questions /
>>>> curiosities about mechanical depth gauges.
>>>> 
>>>> Snoopy's depth gauge is nice and large (about 5" in diameter) so it's
>>>> easy to read. Alec created a nice label for the gauge face which reads
>>>> from 0 to 300 (in feet) with the last fifty feet being marked in red
>>>> to indicate 'too deep.'
>>>> 
>>>> Problem is, when I looked at the depth gauge the other day, I noticed
>>>> that the transparent cover plate on the gauge looked to be quite
>>>> opaque (to the point where I couldn't quite read the numbers or count
>>>> the hash marks). I assumed that there was some moisture trapped in the
>>>> gauge, causing the obscuration. I decided to remove the gauge from the
>>>> sub and open it up to let it dry out.
>>>> 
>>>> After removing the gauge from the sub, I unscrewed three small screws
>>>> around the bezel and popped off the transparent cover plate. It was
>>>> only then that I realized the opaqueness was not caused by moisture
>>>> but a distortion in the clear plastic. The distortion (like super fine
>>>> scratches) appears to be on the outside of the cover, as though it was
>>>> cleaned by something that started to melt the plastic or was left out
>>>> in the sun too long. I don't think either of these explanations make
>>>> sense, but I'm puzzled as to what might have caused it. I might try to
>>>> buff / polish the plastic, or perhaps just replace it with glass.
>>>> 
>>>> I think it's a good idea to stick a dive computer in viewing range of
>>>> a viewport for a depth reading, but I like the idea of having a
>>>> mechanical gauge in the sub as well. A couple of questions that come
>>>> to mind: what is the pressure variation between salt water and fresh
>>>> water? Also, although I didn't find moisture in the gauge, The label
>>>> on the face is wrinkled a bit as though it has seen moisture. Although
>>>> water should never actually reach the gauge, I can see how moisture
>>>> from the inlet tube could find its way up into the gauge body. Should
>>>> I be concerned about drying it out somehow after a dive (especially in
>>>> salt water)? If so, how should I go about it? ~ Doug S.
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