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AD_ward9 · 17th November 2006, 13:47

Quote: (Originally Posted by solocavediver)

Hi,

first of all immense congratulations on the amount and depth of thought that have gone into the Open Rev project.

One question. I read that if the diver attempts to dive the Open Rev without due process, it tries to dissuade him with audible warnings, making it difficult but not impossible to breathe off it, and also by forcibly inflating the counterlungs. As a cavediver I sympathise with this last but I have my reservations - on open circuit I have noticed how little of an air leak is necessary to paste the cave "diver" to the cave ceiling, and if this feature turned itself on by accident in mid-dive (rather than at the start) there might be serious trouble (it wouldn't be necessary to be at deco depths for the trouble to be serious). No doubt jumps to random bits of code are much less frequent with this design than with - erm - other designs, but still, for me it would be a niggle to think about... I would be looking for the manual override valve before anything else got done - even filling the scrubber !!

Cheers,

Charles Read.

Thanks for the input.

We had some less than positive feedback testing this feature. Now it turns off only if the loop is not breathable, and on the surface. We deal with the issues of running trimix in an air only unit differently (not allowing the profile to be downloaded normally, advising the diver to abort continuously etc).

It never inflates the lungs automatically, except on cal, which can only happen on the surface with no-one breathing on the loop and the handsets must be dry.

There is no code to jump to that causes this "feature" to run accidentally. If the microcontroller tries doing it, due to say an internal glitch causing the program counter to skip, then the FPGA overrides it and keeps control.

Cheers,

Alex

17th November 2006, 13:47	#2 (permalink)
AD_ward9 - Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 2,007	Re: Cavediving related query. Quote: (Originally Posted by solocavediver) Hi, first of all immense congratulations on the amount and depth of thought that have gone into the Open Rev project. One question. I read that if the diver attempts to dive the Open Rev without due process, it tries to dissuade him with audible warnings, making it difficult but not impossible to breathe off it, and also by forcibly inflating the counterlungs. As a cavediver I sympathise with this last but I have my reservations - on open circuit I have noticed how little of an air leak is necessary to paste the cave "diver" to the cave ceiling, and if this feature turned itself on by accident in mid-dive (rather than at the start) there might be serious trouble (it wouldn't be necessary to be at deco depths for the trouble to be serious). No doubt jumps to random bits of code are much less frequent with this design than with - erm - other designs, but still, for me it would be a niggle to think about... I would be looking for the manual override valve before anything else got done - even filling the scrubber !! Cheers, Charles Read. Thanks for the input. We had some less than positive feedback testing this feature. Now it turns off only if the loop is not breathable, and on the surface. We deal with the issues of running trimix in an air only unit differently (not allowing the profile to be downloaded normally, advising the diver to abort continuously etc). It never inflates the lungs automatically, except on cal, which can only happen on the surface with no-one breathing on the loop and the handsets must be dry. There is no code to jump to that causes this "feature" to run accidentally. If the microcontroller tries doing it, due to say an internal glitch causing the program counter to skip, then the FPGA overrides it and keeps control. Cheers, Alex
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