Thursday, March 20, 2008

Resmed S8 Version 2

After trying out my original filter mods I found myself working harder to breathe than I did before. Under load, the filter media surface area was just too small to avoid straining the motor, and my lungs. So, I did what any other hacker would do. I multiplied the surface area by 8, and tried again. Problem solved, but, instead of a square patch, I ended up with this 6" white felt tube sticking out of the corner, and the whole thing looks rather obscene. Fortunately I'm now putting the S8 in my night stand, with plenty of ventilation, and you can't see it. What would mom think?

Monday, February 25, 2008

Modding the Resmed S8 CPAP Machine

Finally, after several overnight studies in two different sleep labs, my doctors have prescribed me a C-PAP machine. Basically, it's a bed snorkel. The mask provides pressurized air to your airways while you sleep, reducing the number of times your airways collapse and try to choke you. Now, if you just died in the middle of the night, this wouldn't be so bad. I mean, it's just death, but what actually happens is that your brain, for some odd reason, realizes you are choking, and wakes you up, so you semi-consciously start breathing again. If this happens frequently enough, instead of dying peacefully in your sleep, you wake up feeling like sleeping is very hard work. In other words, barely rested.

So, enter the CPAP machine. Keep your airways full of air, and you don't wake up before choking to death. In fact, you don't choke much at all. No dying, no waking. Just nice even sleep.

The one major problem I see with almost all CPAP machines being sold today, and the Resmed in particular, is that they really are not designed to be all that quiet, but more importantly for allergy sufferers, the filtration really stinks. They fit this tiny bit of polyester fluff in at the entrance of the machine, which basically won't filter out anything but big tufts of cat hair. Everything else in your room, you will breathe, at high pressure. Not a great way to spend the night. They do make in-line filters, but these have a chance of tricking the pressure meters into thinkign your air pressure is higher than it is. It really would have been oh so very easy for Resmed to put in a HEPA filter on the inake.

I should have taken a picture of the intake before I cleaned it for you to see. It was really dirty. Also, instead of providing you with a place to put an intake filter, or at least a place to attach one to, Remsed instead has an opening that makes it almost impossible to attach anything useful to the intake, like for instance, a muffler, or a HEPA filter. Very frustrating. And on top of everything else, my MD prescribed this particular model. Mind you, it works very well, and I understand it's very reliable, and small and portable and the integrated humidifier is pretty sweet, but they are like morticians. They really don't want you shopping around for the best casket, they want you to buy the one they tell you to buy.

So, what is a hacker like me to do? Well, it turns out that in the woodworking and industrial worlds they make these huge dust collection/air cleaning systems. Often a professional mill work or woodworking shop, and sometimes advanced hobbyists, will have large dust collectors with 4-6" ducts running around their shop, sucking up all the wood chips and keeping the shop clean and the air breathable as the craftspeople work. The air gets expelled in a variety of ways, including through these long polyester felt tubes, at the bottom of which is usually a trash bin of some sort. Anyway, the point is, the polyester felt used in these bags normally filters materials down to 1 micron, and after getting nice and packed with wood dust, they get even better, filtering down to 0.3 microns, or about. Not quite HEPA standards (0.3 microns all the time) but MUCH better than what Resmed provides.

So, my solution? Purchase a bag from Oneida Air , cut out just enough filter media to cover the intake, duct tape it in place, and voila, suddenly I can breathe easier at night. :) I've tried it at least one night, and it worked fine, with no apparent change in performance of the CPAP machine. If I was really clever, what I would do is measure the amperage while it runs to see if there's a difference in strain on the air pump with and without the felt, bur right now, my work and school are taking up too much of my time. If I had more time I would have created a felt "pocket" so that I could increase the surface area of the filter. In the next incarnation this is probably what I will do, though honestly it's hard to tell it needs it.

Tuesday, February 5, 2008

The Things We Do for Love


When you are looking at a mid-80s piece of gear the first thing you have to look at are the power supply filter caps, like the one's I pulled out of the Yammie yesterday.

They are in pretty good shape, and will probably last a while longer, but let's face it, these caps are 20 years old. They aren't fresh anymore, and if they go, you risk loosing everything else in the component. As it turns out, the Yamaha, Sumo Polaris and other amplifiers from this era shared the same filter caps.

Today, unfortunately, these caps are extremely difficult to come by. What makes them so special is the 80V rating. You can buy 15,000uF 100V caps right off the shelf, without any problem however they tend to be 120mm long. About 30 mm longer than the originals. The only manufacturer I could find that still makes them is Nippon Chemi-Con, so as a result of this it looks like I'm going to be forced to purchase a small lot of them, and then try to resell any I don't use. Not exactly how I planned on making extra cash this year.

However, if you find yourself in the same boat as I am, and need these caps, send me a yell, I'll be happy to sell you what I don't use. :)

Saturday, February 2, 2008

The Yamaha P2100 Amplifier

The P2100 was introduced in 1977, about 10 years before the P2075, and it's interesting to look at the differences that there are in the circuits of these two amplifiers.

The 2075 is about a 50 W/Channel stereo amplifier. It includes fully balanced inputs thanks to a pair of JRC op-amps, as well as monolithic chip driver and amplifier stages. While you may sniff at the chip amp design, they did a lot of things better in the 2075 than in the 2100. The inputs are truly balanced, many of the audio signal resistors are metal film, copious amounts of bypass capacitors are used throughout the design, and the output stage is heavily protected. Also, the 2075 relies on a lot of ceramic capacitors used as bypass caps.

On the other hand the P2100, while it has a completely discrete audio path, has a single ended input, and almost no bypass capacitors to speak of. The power supply rails go through three different boards with no local capacitor storage at all. While the resistors are mostly cheap carbon composite the capacitors are all polystyrene or tantalum. There's also almost no output protection to speak of. A couple of thermal cut off switches attached to the heat sinks are all you get.

Both amps use several cemented resistors especially near the output stages.

So, the question is what to do, what to do. First, the 15,000uF/86V screw terminal storage caps in the power supply are completely unavailable today. I'm going to have to find suitable substitutes. This probably means designing a new power supply board. If I'm going to do that, I might as well throw in some discrete, zero-recovery diodes, and large value bypass caps.

Next, the cement and carbon comp. resistors will have to go. So will every single electrolytic in the unit.

Last, if I get really ambitious, I'll design a new input driver board to turn the input into a truly balanced design. I'll probably use the design from the 2075 to stay true to the Yamaha spirit.

More when I start ordering parts. :)

Saturday, September 8, 2007

Being a Harvard Extension School Student

It may be obvious if you think of it, but in your life, the most important upgrades you can make is to yourself. That is, to upgrade your capabilities mentally or physically. As a result of this kind of thinking I have begun taking courses at the Harvard Extension School (HES).

One of the most frequent difficulties I have is explaining to others what it means to be a student of HES, compared to a "real Harvard student." I'll try to answer this for students, potential students, parents and anyone who wants a quick overview of how the two schools are different.

As the HES website notes, of all the colleges that make up Harvard University, only two grant undergraduate degrees, HES and the Harvard Faculty of Arts and Sciences (FAS).


We can divide the differences between HES and FAS in the following broad categories:
  • Admissions
  • Size
  • Course selection
  • Price
  • Community
  • Props
Admissions
HES is easy to get into compared to FAS. This is one major reason HES students just don't get the respect. More below. Harvard keeps a severe boundary between admissions to HES and FAS. The only legitimate way to get into FAS is to go through the FAS admissions process. There is no transfer of students between the two schools.

Size
Harvard FAS has approximately 6,000 undergraduate students enrolled in any given year, while HES has about 600. Also, according to my calculations, HES accepts around 120-180 degree applicants per year. So one way to look at it is that HES is a very small college in a huge university. As a student, the relationship you have to the undergraduate office is really intimate. They know you. Your not going to get away with much, so be careful who you flip off while driving or walking through Cambridge, it could have an immediate effect on your academic progress.

Course Selection
Academically, the biggest difference is not in quality, but in quantity. If you look at the picture above you'll see the Harvard Faculty of Arts and Sciences course catalog on the top, with the HES course catalog on the bottom. The difference is HUGE. FAS offers many more courses, and many more degree specialties. While HES offers many areas of "serious" academic study, it offers no practical art class and only 5 music classes, with only one touching on western art music (i.e. classical). If I may launch from the words of Professor Robert Levine, with apologies, who argues that classical music is essential to the educated mind, if not soul, this lack of potential for a classical musical education is a place where I really wish FAS would improve and then promote. It would give the school a richness I think is missing.

As far as academic quality and rigor of study, HES shares many of the professors from other Harvard colleges, including not only FAS but Harvard Medical School as well, and some classes are identical, given by the same teachers, using the same materials and grading. Indeed, in order to get an HES degree, you must complete at least 52 units with Harvard faculty.

There is however a very bright side to all of this. Keep your GPA over 3.33 and you can apply for special student status, allowing you to take courses through FAS (at full FAS prices!) during the day. A major incentive not to ever get an F.

Price
The prices for courses at HES are very reasonable, it's like an expensive community college. Undergraduate, for credit courses are around $700-$900 each.

Community
The other big way in which HES is different than FAS is the sense of community. There are student organizations and student led activities but with the average student working full time and not living on campus it doesn't feel like a college experience to me, and that is a sad thing. I regret not only not having finished my undergrad when I was young but also not having made the lifelong friends people make in college.

Props
What the social standing / pecking order is of HES students compared to FAS students is a huge and real issue. It is too big a topic for this entry but I am going to spend some time researching it and writing on each aspect of it in the future. But, the quick answer is, right now there isn't much consensus even within the university. Students from FAS and HES don't actually know how to act around each other. It's pretty funny sometimes, sometimes it's sad. Do FAS students say they go to Harvard or FAS? Should extension school students say they go to Harvard or HES? Is that discriminatory or honest? See how messy this is? It's like a bad joke that begins:

"Two Harvard students walk into a bar, the bartender looks up and says ......... "

Works Cited
Even though this IS just a blog, Harvard (FAS and HES) takes plagiarism very seriously, so to avoid being accused of not citing sources 50 years from now as I'm about to accept my Ph.D. (hah!) I would like to note my sources. Much of the materials here are from the HES and FAS websites, and catalogs, especially the Harvard Fact Book, and the Harvard at a Glance web page.

Tuesday, June 19, 2007

There's no Such Thing as a Good Remote

My perfect remote control is an old Marantz RC2000. It was a hungry beast when it came to batteries, but it was an awesome remote when it came to behaving just like you wanted it to, visibility and reliability.

The Logitech Harmony 520 remote, by comparison, was svelte, a battery miser, and an absolutely selfish, manipulative bitch of an appliance. I took particular glee in recycling it's innards when it froze up on me and no amount of replacing the batteries would work. About a week after I had thrown it out, Logitech sent me a very nice e-mail informing me about the remote's "safe mode" boot process. Sorry, too late. I've moved on. Damned if I want an appliance in my life which needs a "safe mode" to boot. Damnit, would it have cost them that much to include a reset button underneath?

I purchased a new Marantz 1400 from Accessories4Less which made it a bargain, and it arrived promptly, with no fuss.

The good news:

  1. Easy programmability, not only text, and buttons but especially, the MACROS are a breeze compared to the lame ass browser/wizard based interface Logitech uses.
  2. Most devices were built in.
The bad news:
  1. Really poor visibility of the LCD
  2. Won't learn new Samsung TV commands (but built in Samsung codes work), leaving me without the compass buttons.
  3. Theta commands not built in.
Am I happier than I was with the Logitech? Yes! Am I completely satisfied? No.

For those of you out there with remotes which do everything you need, tonight, when you are watching Stargate SG-1 re-runs in Dolby Surround, hold the remote close to your breast, and tell it how lucky you really are.

Sunday, June 10, 2007

The New Era of Low Quality Appliances

You know, I hate to say this, but my experience lately with high technology gadgets has been really terrible.

Let me explain. Over the last two years I've invested in the following:

  • Samsung 50" 1080p DLP TV
  • HP PC
  • New NVidia 7600 video card
  • Hauppague WinTV-PVR USB2 TV recorder
  • Logitech Harmony 520 remote.
  • Netgear USB Wireless adapter
  • Netgear WGR614v4 Router (not so new)
  • Pentax Optio pocket digital camera
  • Lumix Digital camera
  • Panasonic 3 station phone system
In almost every case, there was some disappointment involved.

First, I really didn't want a 50" TV, but my GF complained about the 37" TVs we saw being too pixilated, and Samsung was really the only brand she liked. So four hours of arguing later, she sees the latest 50" DLP and says "Oh, that's nice" and I'm so frustrated I say "DONE!" and we buy it, for our tiny living room with the couch 5' away from it! Take it home, lug it up the stairs myself, turn it on, and after it's finished scanning all the cable channels, it's working perfectly. For 6 hours. Call up Samsung on 6/2. 6/9 they call me and tell me that the parts they ordered aren't in yet, will have to wait until 6/15 or so to get the repair person out. I'm out $2k for six hours of TV. Also, now that the TV is in, my GF says she doesn't care if I get a small TV or not. The she tells me in the same breath they aren't as good. Lesson learned: Pay for the delivery, so that if the thing breaks you can have them haul it out and exchange it for you.

The HP PC which I am typing this on was sold to me as having half a gig of memory, expandable to 4. Well, the truth is, it had less than 512 Megs usable because part of that was used by the on-board graphics card. And despite the Staple's salesperson's confident assurance that it would take 4 Gigs, it won't. On the plus side, (probably thanks in part to the diligent work of US Attorney's before the Bush purge) the $50 rebate offer was actually paid in a timely manner.

The WinTV-PVR/USB2 appliance stops working if the CPU gets too hot, which is often unless you add a heatsink and fan.

For better performance with Half-Life 2 I purchased a new NVidia 7600 card at Best Buy. The NVidia card keeps having random stuck thread issues when replaying things recorded in Windows Media Player, it's especially bad if I have other windows open.

The Logitech Harmony 520 remote control is now sitting in the trash, because after having to change a configuration again through the stinking Hell Hole of a web site they use to manage your remote, it froze up on me and there's no way to reset it to the original factory conditions. No real "reset" button on the bleeding thing.

Both networking devices purchased from Netgear also are also having reliability problems. I know for a fact that the router overheats, and suspect the USB adapter does as well. How do I know? Well, after adding heat sinks and fan to the WGR614v4 router, the thing ONLY breaks down when the fan stops working. I would totally throw it out if the Linksys routers worked with my VPN software which I use to teleconference from work. But guess what? Even though Linksys and my VPN software are made by different divisions of Cysco, they actually don't work right. Also, I find Linksys installation software to be buggy, and din't integrate well with Windows XP on my previous PC. So I'm basically F*d.

The funny thing is, the Netgear wireless router appliance is about the same size, shape and has the same basic layout as the Hauppauge! WinTV-PVR appliance. Makes me wonder if they share the same industrial design house. Also, I've been really tempted to buy the new Netgear wireless media devices, so I can hook it up to my new Samsung DLP TV (if it's ever working again) but I read a couple of reviews online that complained about it inexplicably dropping out just like the problems I've had with their router and USB wireless adapter. Makes me want to stay away from it unless I can get an Ethernet cable run to the living room.

The Pentax Optio camera froze during a download and wouldn't come back until after I threw it into the trash. My GF rescued it so it's hers. The Lumix camera on the other hand has worked great, but it's sure bulky by comparison.

The Panasonic wireless phone works fine, but if the power is out for too long the base station forgets what time it is. Crap, it's 2007, don't they have that figured out yet?

So, I guess the point to all of this is, I used to like improvements and upgrades, but damn, with the low reliability of electronics being sold these days, I really am put off on ever upgrading anything again. I don't care if they release 100 Gbyte wireless routers. So long as the one I have works, I'm leaving them alone, because it seems to me that I'm going to have to buy 2 of anything in order to get 1 that works. So from now on, I'll double the price of anything I buy before I decide to purchase a new one or not.

Is it wrong of me to want things that are simple, and reliable? I don't want Microsoft running my refrigerator, I don't want a USB adapter in my car, I don't want an operating system in my camera, and I don't ever, ever want to wait for my phone to boot up. I press the button, and it is waiting for me to dial. End of story! No flashing lights, no slide shows as it figures out that it's a phone, nothing.

Based on all of this, go ahead and ask me how many years it's going to be before I give up my landline telephone.