Open source, I see problems. Questions.

AD_ward9

That is correct.

And being an expedition unit, there is no cert card on earth needed because no agency certifies someone for expeditions.

Cheers,
Alex

Genesis

Let me know when they're actually available and you can quote a price.

There does seem to be this problem with actual shipping dates and quoted prices "at the outset" .vs. "when actually shipped" when it comes to commercial units.....

2stoned

Alex…
The computer, assuming it will be a full deco computer…
As indicated it will read the actual gases breathed when calculating deco requirements:
a full reading of O2, He, N2 and preferably no presence of CO2.
As I understand this:
This reading is done in the plenum after the CO2 absorption.
With the Auto ShuDBoF now separated, does that mean that the ShutOf valve is positioned prior to the “sniffing electronics” so that the Diluent gas used in BailOut-SC or -OC mode is "sniffed" and included in the calculations for stops and deco?
Thus that the Computer always knows what you breathe as long as you stay on the loop (SC and OC feed through the Rebreather inhale hose and OverPressureValve is in exhale lung).

Is there an option to tell the computer that you switched to a new gas, as on separate OC, so that these gasses can be calculated for deco requirements? (Gas choice ON/BAIL/OFF) (Can you program-in gasses?)

I hope that this deco-comp will not Lock-Out the diver, when he finds himself in an emergency, like helping someone to surface, and then go down to deco.
-A safe Rebreather should never let you down. Please none of this “USE TABLES”

Alex, we are very ready for a new thread on the rev4.
These threads are getting hard to read (the info is spread out wide and I have a short memory).
When you are ready, can you start the new thread with a summery/presentation of your baby.

I need to say this:
Alex thanks for your endurance and hard work in relating and sharing this info with us.
What a place this is, this forum has lots and lots of smarts and brains.
I am very impressed.
Wow!

__________________
Sten.

The only man that always had all his work done by Friday, was Robinson Crusoe!

www.rebreatherworld.com - Is going down in silence - Staying longer in stealth and style - Diving first class, all the way!

AD_ward9

You have identified an area very worthy of debate.

The sensing is the gas going into the breathing hose, prior to the shut off valve.

What happens on deco if the user has bailed out, is that it assumes the gas is what is in that space. If the user is on O.C., then there can be quite an error. This is the reason we moved the exhale valve from the mouthpiece to the exhale bag: it means gas flows past the exhale mushroom and does get into the loop.
Correct, and an error if the user is not on the loop (ie an error in the calculation).
There is no means to do that right now, but it may be necessary.
I agree, tables is not really the solution though divers should always have them.

At the same time, we do not want divers telling the unit what gas they think they are using. Too often it is in error, especially with certain boat operators who do not seem to have the faintest idea of blending when they provide gas: we give the mix free if it is out by more than 2%, but I have bought gas at silly cost on some boats where even the O2 is out by 50% from that ordered and what the He is is anyone´s guess as there was no analyser on board and no scales to make a guess with.

At the moment, if the shut off valve closes, it will continue with the same dil gas as the diver has been using. This is not a satisfactory solution.

We are going to have to find a better solution for the deco calc in this bail out condition. We are hoping the moving the exhale valve gets enough gas into the sample area to do something. We are also trying a shut off valve which does not close entirely, but only 95%, so some gas gets around the loop: it is enough in the case of a flood to stop water in the hoses. An area needing development ...
I have the same problem. The Open Revolution area should be up soon. Very soon, with all these things separated into different threads.

Thanks again for the time to think these things out so carefully.
Cheers
Alex

2stoned

What if the "sniffer electronics" where to read from samplings.
Working something like this:
Direct the gas through a smaller tube to blow by the "sniffers".
This way, through simple valves or switch-block, (if made simple and thus "safe") you could sample from different areas, Ex.:
- Plenum (after absorbent, as now)
- Exhale Counter-Lung (diver CO2 production)
- Inhale hose (after Diluent entry)
a) Thin tube to point just prior to mouthpiece?
b) Through a hydrophobic membrane, from within the mouthpiece?
- Outside surface air (needs a self-closing seal, pull and hold to keep open)
- Outside with a small chamber (balloon?) for gas testing.
The system could default to Plenum or Inhale hose.
This gives the option for the system to check various areas for safe status.

I understand that there might be issues if the gasses are not sufficiently blended when the samples are being taken. Hence the reason of generally choosing to inject O2 early in the loop to ensure a good blend through the scrubber, before testing the ppO2.

If from all valves inducing gasses into this blend, the gas was send by a twirling tube or towards a whirled cone, a venturi effect would be created that might assist in these gasses blending.

The dream of having a computer know and calculate on the gasses the diver is actually breathing.

Idear on (ambient pressure) Valve/switch-block:
Make it a low cylinder shape with periferal connections to sampling points (starshape).
Have the sampling taken through center top or bottom.
Selecting the sampling from a revolving inner valve.
Smallest possible common area.

OK now! Go to work and make this thing happen!

__________________
Sten.

The only man that always had all his work done by Friday, was Robinson Crusoe!

www.rebreatherworld.com - Is going down in silence - Staying longer in stealth and style - Diving first class, all the way!

AD_ward9

One would need gas flow up the hose. That is quite complex because it must from from somewhere to somewhere, and be forced.

There are only two places one wants to sample: the gas the diver is breathing comes from either the scrubber or the bail out. Therefore post scrubber is fine. The bail out issue is more complex.
Why would the gas flow along the narrow tube? The main flow is a huge tube (over 1000sqmm cross sectional area).
Can you supply the detail, or the magic wand?
Cheers
Alex

divetheworld

Now that is funny!!!

__________________

Sponge-Bob

Hi,
The save the looney part also disturbs me somewhat. My experience is that most divers are looney and most over estimate their ability. Messing with their breathing rates will only increase their descent into the pit of panic! Through no fault of his own, like going to the aid of another diver for instance, a diver may find himself beyond the limits of the unit. It needs to be his saviour, not his enemy.

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AD_ward9

We received quite a lot of comment on similar lines, and have listened to that. We agree on the common distribution of loons in the dive community.

In response to the feedback, the shutoff valve and "Save the loony" features have been reconfigured as follows:

1. The shutoff valve is shut upon power up, and shuts upon power down. When shut, it blocks just over 90% of the gas in the loop. There is a manual override (pulling a cord), but unless all of the predicates needed to keep the valve open are true then it will shut as soon as the diver lets go of the cord/pull tag. The 10% bypass is needed for the loop to recover when the diver is on O.C. (from the ADV).

2. Until the checks are finished, the shutoff valve is shut, apart from the positive and neg pressure tests: the former is automatic, the latter is manual.
This means if the user has none done the checks, then the loop can't be breathed from.

3. If the unit is underwater, then the checks are skipped and the unit goes immediately into operation. Underwater means more than 3m depth and the wet contacts are active.

4. Any time the loop is not breathable, the shut off valve is shut. This is a PPO2 of less than 0.21 or more than 1.6. There is no manual O2 inject, only DIL inject via the ADV, so shutoff pulls gas from the ADV on descent.

5. The unit never allows PPO2 to fall below 0.21, even when off, so long as there is an O2 supply. Even if the unit is switched off, it checks the PPO2 level and injects gas.

6. The limits are checked now based on the last dive and a lockout period.
The lockout prevents the unit going into dive mode after predive checks.
The lockout conditions are based on the previous dive, and come into play only when the dive has finished (i.e. the unit is not being breathed from for more than 15 minutes or the unit is dry on both handset and base).
The period of the lockout depends on what is done:

• Depth limit +20%, 1 day.
• Depth limit >20%, 1 week.
• Dive greater than limit with use of He mixes on air unit, lockout until serviced.
• There is no lockout on deco breaches.

Further comments welcome.

On the 10m or 3m issue, the unit under the previous configuration was locked out, so it was just like a free dive. There is no risk of burst lungs: the path to the overpressure valve is still open - the shutoff only shuts the path before the ADV so the diver has to breath from the ADV. In the pictures we posted, you can see the ADV is connected to the mouthpiece via a large diameter hose, and can meet EN250. The issue on that is the mushroom valves. I will post the cross section of the mushrooms that are the main flow restriction to explain this: mushrooms are the main reason ADVs fail EN250.

On the Micropore EAC sealing issue in your quote, Micropore are changing the seals for these O.R. rebreathers so the cartridge itself has a disposable seal, just like an oil filter on a car. This gives around 10% more active area for the cartridge also, hence 10% more scrubber life.

Alex

Genesis

Locked out until serviced? Not because the unit detects it can't be safely used - but because it doesn't like what you did (and obviously safely returned from, or you wouldn't be in a position to use it again, would you?)

Do you really think people will buy this thing Alex with that sort of nannyism built-in? More to the point, why should anyone tolerate this sort of nonsense?

This is like a car that refuses to start until towed to the dealership if you speed while operating it but only if you actually wear a seatbelt while speeding - otherwise it won't start for a day or a week, depending how fast you were going.

So if you do something radically unsafe, then it locks you out for a day or week. But if you do something safer (by using a non-narcotic breathing mix) but haven't got your formal "nanny state" card to go with the safer practice, then the unit turns into a worthless but very expensive paperweight.

I think you can figure out what my response to this sort of stupidity is, and its not printable in polite company.

Such a product would never sell in any other product, and I suspect you're going to get a similar surprise here as well.

Oh, I hope you fully disclose all this before you take anyone's money and have a documented paper trail evidencing their full, legal consent (and no, having some instructor tell you won't cut it.) Otherwise I suspect you'll have a really serious legal problem when your kit intentionally disables itself, thereby rendering itself intentionally unfit for the purpose it was sold for!

__________________
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