[PSUBS-MAILIST] Compass Choice

[Smyth, Alec]

Hi Alan,

I think Triton use a PLC, because I spied a switch labeled "PLC Off" on their control panel. Years ago I got a PLC, a touch screen, and all the associated sensors together, and wrote the code for it. Cliff and I picked the same equipment and shared our code, and you may have seen his R-300 runs everything off a touch screen. It's a very neat approach because you can let the PLC concentrate on background monitoring (e.g. O2 levels, pressures) while letting the pilot concentrate on the driving. Personally, I'm headed in the opposite direction nowadays, designing my new boat to have minimal electronics for reliability and ease of maintenance. But I still have a box full of all this hardware, and if anyone is interested in installing it on their sub they can have it for a tiny fraction of what it would cost new.

A PLC is a sort of industrial computer, much simpler and more rugged than a PC. It has no hard drive to fail, and you won't get the "blue screen of death" like on a PC. The logic runs in a continuous loop, monitoring parameters and taking action when conditions you specify are met. For instance, for life support you can say if cabin pressure drops below X, then open a valve to inject O2. Later in the loop, a similar clause would close the valve if cabin pressure rises above Y. The scrubber would remove CO2 continuously, and the PLC add O2 to keep the cabin pressure between X and Y. Other alarms would go off if tank pressures are getting too low, if max depth is exceeded, etc. etc.


Best,

Alec



From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Alan James
Sent: Tuesday, January 14, 2014 2:02 AM
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] Compass Choice

Hi Douglas,
I'll do a bit of homework on this.
I had a look at the Triton 3000 when it visited N.Z. & it was monitoring
just about everything off a computer. They were talking of moving to
smaller computers & maybe strapping them to their thighs, so that the screen
didn't impinge on their view. Other submersibles I've seen similarly monitor
a lot of functions off the computer.
I like this little computer with a 4.8" screen.
http://www.dynamism.com/top-notebooks/viliv-s5-premium.shtml
It runs windows so would be compatable with the Ocean Server compass.
Cheers, Alan


________________________________
From: Douglas Suhr <spiritofcalypso at gmail.com<mailto:spiritofcalypso at gmail.com>>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org<mailto:personal_submersibles at psubs.org>>
Sent: Tuesday, January 14, 2014 4:59 PM
Subject: Re: [PSUBS-MAILIST] Compass Choice

Nice find Alan. I'm going to spend some time looking over that site. I have to admit though, I feel the same as you in terms of not wanting to run my compass off a computer. To me, computers should be benefitted from but not relied upon unconditionally. ~ Douglas S.

On Mon, Jan 13, 2014 at 10:45 PM, Alan James <alanlindsayjames at yahoo.com<mailto:alanlindsayjames at yahoo.com>> wrote:
Hi Jon,
I found this off the shelf unit for $250- (made in USA) It is designed for marine applications
& has yaw, pitch & roll which is a G.L. requirement. So it's looking attractive.
http://www.ocean-server.com/compass.html
It looks like I would have to run it off a computer though, which I didn't want to do,
but may be forced down this path.
Alan


________________________________
From: Jon Wallace <jonw at psubs.org<mailto:jonw at psubs.org>>

To: Personal Submersibles General Discussion <personal_submersibles at psubs.org<mailto:personal_submersibles at psubs.org>>
Sent: Tuesday, January 14, 2014 2:09 PM

Subject: Re: [PSUBS-MAILIST] Compass Choice


A tilt-compensated electronic compass (three axis, plus three axis
accelerometer) would work connected to a small microcontroller like the
Arduino UNO.  The HMC6352 was the standard but Honeywell stopped
producing them.  There are others however but probably more expensive.
The display could be a nice four digit LED (under two inches).

Jon


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