Path: Newsgroups: alt.sport.dive.rebreather Distribution: world Followup-To: References: From: Charles Read Organization: Subject: Home Building. Keywords: Hi, I am trying to do a homebuild. It has just passed its Order of the Bath (i.e. I put it in nice warm bathwater & it doesn't leak & I can breathe it). OK if I try out some ideas for it on this NG and get some feedback?? Question 1: when it's been tested in real water, next step is to give this baby some electronics. I have a couple of O2 sensors and am thinking of ways to rig them up. I THINK the best way is to have a single display that usually displays the main O2 sensor reading, but you press a button and it gives you a backup reading instead (or one of 2 or more buttons for multiple backups). That way you have instant access to what the other sensors are saying, but not too much clutter. And some kind of buzzer that goes off if ANY sensor thinks things are going wrong. Question 2: I have written a dive computer program using Buhlmann but I understand this is not exactly state of the art. I have read up a bit on the VPM method but info is scarce - I tend to have to reverse engineer other people's computer programs to work out what constants they're using - so help with this would be greatly appreciated. Lots more questions but those'll do for starters. Cheers, Charles Read. Path: Newsgroups: alt.sport.dive.rebreather Distribution: world Followup-To: References: <3944a035.84667447@news.cis.dfn.de> <8hrgld$lgv$1@pegasus.csx.cam.ac.uk> From: Charles Read Organization: Subject: Re: Home Building. Keywords: Karl wrote: > Ok, for that I would suggest to show all 3 Sensor-Readings >at one time, because the speed of changing the readings >can differ between the sensor-cells. >If you could not see the 3 values at the same moment, >there migt be spooky situations where the alarm is on >and you can not find a reason. Yes, but on the other hand, ONE display of PPO2 might be clearer and easier to read in a hurry. In the same way, I'm wondering about maybe an analogue display - you remember when the Americans introduced digital speedometers on their luxury cars? I think it was BMW that pointed out this slows the reaction time of the driver. They have not become popular. Yet everyone seems to go for digital meters to display PPO2. I'm still thinking about it, hence these postings. Maybe, like this (thinking as I write): an analogue display of the master sensor that is controlling the solenoid. Three red l.e.d s that mean "Sensor 1,2 or 3 thinks you're hypoxic". Three green l.e.d s that mean "Sensor 1,2 or 3 thinks you're hyperoxic". Three yellow l.e.ds, meaning "Sensor 1,2 or 3 is the master sensor". A switch to control which sensor is master. 3 pushbuttons that temporarily cause the analogue display to show a reading for one of the non-master sensors (for 10 seconds or so). 220 588 article Path: pegasus.csx.cam.ac.uk!server1.netnews.ja.net!fu-berlin.de!newsfeed.direct.ca!btnet-peer0!btnet!landlord!stones.POSTED!not-for-mail From: "ww" Newsgroups: alt.sport.dive.rebreather References: <3944a035.84667447@news.cis.dfn.de> <8hrgld$lgv$1@pegasus.csx.cam.ac.uk> <8i4p9r$b5j$1@pegasus.csx.cam.ac.uk> Subject: Re: Home Building/Engineering Project. Lines: 81 X-Newsreader: Microsoft Outlook Express 4.72.3110.1 X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 Message-ID: Date: Thu, 15 Jun 2000 22:06:39 +0100 NNTP-Posting-Host: 212.159.23.103 X-Complaints-To: abuse@plus.net.uk X-Trace: stones 961104231 212.159.23.103 (Thu, 15 Jun 2000 22:23:51 BST) NNTP-Posting-Date: Thu, 15 Jun 2000 22:23:51 BST Xref: pegasus.csx.cam.ac.uk alt.sport.dive.rebreather:588 www.pendant.free-online.co.uk its worth a look at this display for the ccr 2000 for some very good ideas. Charles Read wrote in message <8i4p9r$b5j$1@pegasus.csx.cam.ac.uk>... >Karl wrote: > >> Ok, for that I would suggest to show all 3 Sensor-Readings >>at one time, because the speed of changing the readings >>can differ between the sensor-cells. >>If you could not see the 3 values at the same moment, >>there migt be spooky situations where the alarm is on >>and you can not find a reason. > > > Yes, but on the other hand, ONE display of PPO2 might be clearer >and easier to read in a hurry. In the same way, I'm wondering >about maybe an analogue display - you remember when the Americans >introduced digital speedometers on their luxury cars? I think it >was BMW that pointed out this slows the reaction time of the driver. >They have not become popular. > Yet everyone seems to go for digital meters to display PPO2. >I'm still thinking about it, hence these postings. Maybe, >like this (thinking as I write): > >an analogue display of the master sensor that is controlling the solenoid. > (well lit, situated on left wrist where you can read it!) >Three red l.e.d s that mean "Sensor 1,2 or 3 thinks you're hypoxic". >Three green l.e.d s that mean "Sensor 1,2 or 3 thinks you're hyperoxic". >A switch to control which sensor is master. >3 pushbuttons that temporarily cause the analogue display to show > a reading for one of the non-master sensors (for 10 seconds or so). >Three yellow l.e.ds, meaning "Sensor 1,2 or 3 is on display". >A buzzer that goes off if any red or green l.e.d. is lit. > >>You should also think about the hypothetical case there 2 cells >>show the same but wrong reading only the 3rd call is good. > >Thanks Karl, an excellent suggestion I hadn't thought of. How about this. > >Rule 1: if any serious sensor disagreement occurs, you "turn" the dive. > >Rule 2: The place where >breathing gas enters the loop is RIGHT NEXT to the sensors, in a >cavity with a non-return valve. By twisting a lever one can cause the sensors >to read PPO2 in the cavity instead of in the loop. Since one knows the FO2 >in the cavity, the faulty sensor can be detected. Too complicated? >Maybe. If so, breathe open circuit for a bit and simply flood the >whole loop with fresh breathing gas. One has a depth = PPO2 table for ones >chosen breathing gas strapped somewhere conspicuous, if one doesn't >know it by heart. BTW, reason I only got 2 sensors is I want to postpone >some expensive purchases 'til I'm sure this engineering project >will work. > > >>I prefer engineering, as homebrew does not sound that good when >>talking about live-support systems. > >Yes the British are funny about that sort of thing. When you see >the soldiers of the British SAS, very tough dudes, remember that >as of a few years ago bits of their kit (buckles, ammunition clips, >belts etc) were partly homemade because the quality of the official >ones provided was appalling (they fell apart!). We continue to >be "Lions led by Donkeys" (French observer of Charge of light brigade). > >Cheers, > > Charles Read. > > >Charles J. Read (Dr.); C.J.Read@dpmms.cam.ac.uk, web http://read.trin.cam.ac.uk >phone 01223-338440 or from abroad (Int'l access)+ 44-1223-338440. Snail Mail: >Dr. C.J.Read, Trinity College, Cambridge, CB2 1TQ, UK. > > Path: Newsgroups: alt.sport.dive.rebreather Distribution: world Followup-To: References: <3944a035.84667447@news.cis.dfn.de> <8hrgld$lgv$1@pegasus.csx.cam.ac.uk> <8i4p9r$b5j$1@pegasus.csx.cam.ac.uk> From: Charles Read Organization: Subject: Re: Engineering Project - I dived it! (to 10 feet). Keywords: "ww" wrote: >www.pendant.free-online.co.uk its worth a look at this display for the ccr >2000 for some very good ideas. Right. Digitally calibrated O2 sensors are another tradeoff aren't they; the linear correction can be perfectly linear, calculated to N decimal places by the onboard computer, whereas an analogue circuit will never be quite linear, especially when compensating for temperature changes. But, if the computer should fail, ones analogue backup (if any) then won't be calibrated at all... I've been making an O2 sensor circuit and I note that the temperature dependence of the sensor is not vast - 0.21 atm at warm room temp becomes 0.224 in the fridge - but just enough to need correction. But back to fundamentals, this weekend I took my first ever dives with the EP (engineering project). "Dive" 1: found out quite how positively buoyant the EP was. Could not submerge! Took 16 pounds of extra weight to (nearly) compensate. EP is about 17 pounds positive, mainly due to the largeish counterlung. Dive 2: submerged to the mighty depth of 10 feet and, while noting that it still didn't leak and was still breathable (I refilled manually with fresh air one breath in two), nonetheless it is very cumbersome and gets in the way of nearly every other piece of kit I want to reach. (this was the simplest design I could find on the Net, the TP2000 (see http://www.nwdesigns.com/rebreathers/TP2000/Default.htm), which mounts at the front not the back). I shall rethink the layout and fit an O2 sensor before returning to the water. cheers, CJR 220 593 <8iqogt$5h8j0$1@fu-berlin.de> article Path: pegasus.csx.cam.ac.uk!server1.netnews.ja.net!fu-berlin.de!uni-berlin.de!max4-99.hrz.uni-giessen.DE!not-for-mail From: Karl.W.Kramer@physik.uni-giessen.de (Karl Kramer) Newsgroups: alt.sport.dive.rebreather Subject: Re: Engineering Project - I dived it! (to 10 feet). Date: Wed, 21 Jun 2000 15:55:09 GMT Organization: http://rebreather.de Lines: 25 Message-ID: <8iqogt$5h8j0$1@fu-berlin.de> References: <3944a035.84667447@news.cis.dfn.de> <8hrgld$lgv$1@pegasus.csx.cam.ac.uk> <8i4p9r$b5j$1@pegasus.csx.cam.ac.uk> <8intor$6j5$1@pegasus.csx.cam.ac.uk> NNTP-Posting-Host: max4-99.hrz.uni-giessen.de (134.176.249.99) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: fu-berlin.de 961602910 5808736 134.176.249.99 (16 [2394]) X-Newsreader: Forte Agent 1.5/32.451 Xref: pegasus.csx.cam.ac.uk alt.sport.dive.rebreather:593 On 20 Jun 2000 14:06:19 GMT, Charles Read wrote: > EP is about 17 pounds positive, mainly due to the >largeish counterlung. Hi Charles, it might be a good idea to dive with "empty" conterlungs. This means: when (assuming an LungAutomaticRegeneator) you nomally inhale the counterlungs bottom out, then you inhale more than normal the regulator adds extra gas. You can use this as some sort of fine-BC, with access gas is remouved trough your nose. A too big counterlung in this concept still means a "rocked out of the water" risk. p.s. sorry, I have not enought time at the moment to answer the set of threades you launched in your last bulletin. 42, thanX for the fish, Karl http://rebreather.de (Rebreater Diving) (plus more than 1800 SCUBA-Links) news:alt.sport.dive.rebreather (is my favorite Newsgroup ) mailto:KarlXXX@Rebreather.de (Delete the XXX to reach me!) . Received: from emu.dpmms.cam.ac.uk (cr25@emu.dpmms.cam.ac.uk [131.111.24.1]) by read.trin.cam.ac.uk (8.9.3/8.8.7) id SAA01365 for root; Sun, 25 Jun 2000 18:00:32 +0100 Received: from [131.111.8.40] (helo=puce.csi.cam.ac.uk ident=exim) by emu.dpmms.cam.ac.uk with esmtp (Exim 3.01 #5) id 136Ghq-0002SM-00 for C.J.Read@dpmms.cam.ac.uk; Sun, 25 Jun 2000 19:00:30 +0100 Received: from [212.139.128.4] (helo=pdbs0-uk0.x-stream.co.uk) by puce.csi.cam.ac.uk with smtp (Exim 3.13 #1) id 136Ghp-0000n1-00 for C.J.Read@dpmms.cam.ac.uk; Sun, 25 Jun 2000 19:00:29 +0100 Received: (qmail 29344 invoked from network); 25 Jun 2000 18:00:26 -0000 Received: from unknown (HELO colin) (212.139.190.184) by pmail0-uk0.x-stream.co.uk with SMTP; 25 Jun 2000 18:00:26 -0000 Message-ID: <000b01bfdecf$7059e7c0$b8be8bd4@colin> From: "John Wych" To: Subject: Diy Rebreathers Date: Sun, 25 Jun 2000 19:01:50 +0100 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0006_01BFDED7.D165AE20" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2919.6600 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6600 This is a multi-part message in MIME format. ------=_NextPart_000_0006_01BFDED7.D165AE20 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hi Charles , I hope you don't mind me sending you an e mail , out of the blue as it = were. I found your enquiries on the deja rebreather site when you were = discussing the broad points about electronics in rebreathers. That is just what myself and a friend are in the middle of doing , at = present we have a complete closed circuit rebreather with 3 sensors = directly displayed on 3 lcd displays , this alone can be used to fly = the unit manually coupled with this is a secondary bar graph display , = totally seperate to the lcd displays and a set point injection circuit = also driven by the sensors. We started off with the equilivent of 3 nitrox analyers which were put = in a waterproof housing , hence a basic closed circut control system , = as the AARG one is . We are noe also looking into the addition of a CO2 detection device that = can be put into the loop as an alarm for scrubber failure before you = lapse into unconsousness!. I see you have an interesting article on an IR chip that will do this , = do you know any more details ? The best solution as far as the easy answer is Three sensors with three = displays either bar graph , led or lcd digital , , it must be 3 as if = one sensor fails you can then decide which it is from the other one, if = 2 go down at the same time you are very very unlucky!! Hope this is of some help,by the way I enginnered my rebreather using a = drill, jigsaw, hot glue gun in my garage, if it works why not !! John Wych Chorley Lancashire To: "John Wych" From: Charles Read Subject: Diy Rebreathers Cc: Bcc: Dear John, it seems clear I should meet you and your friend and we should pool information resources (without necessarily drawing the same conclusions). I don't know where you can buy the IR CO2 sensors or how much they cost. I might chat up someone in the University physics department - or even a medic, they're interested in CO2 same reasons as us - about this. My construction efforts are well behind yours. Now I come up to Lancashire quite frequently, as you'll have seen from my webpage my favourite cavedives are around Ingleton, also I like Wastwater as a general open water dive. So if that's OK I'll let you know when I next come up there with the RB and we can get together with a bit of luck. My engineering materials have been: rubber, plastic tubing, fibreglass, duck tape (to hold the metal gauze in place at the ends of the scrubber canister), hose clamps, "stop washers" from B&Q to make the valves, plastic washing up scourers to further discourage the sodalime from making a bid for freedom, (yes you can breathe quite freely through a plastic washing up scourer) bungee cord, weights. My sodalime has been home made from calcium hydroxide, sodium hydroxide amd a little water mixed in a food processor - I kind of assumed people wouldn't sell me the ready made stuff if I hadn't taken a course! I'll let you know when I'm next coming up there. All the best, Charles Read.