โJul-13-2017 08:02 AM
โJul-24-2017 08:52 AM
ktmrfs wrote:
... for the resmed you can buy a complete ready to use 12-24 DC to DC converter either from resmed, or from battery power solutions. BPS converter when I bought it was just over $50. works on the airsense 9 or airsense 10. comes complete with the correct plug.
โJul-24-2017 08:12 AM
JimK-NY wrote:
I have my own tales of incompetence and ignorance by sleep study physicians. I had a sleep study immediately after seeing a dentist. I was uncomfortable all night and could not sleep. Finally I dozed off for a few minutes. The study should have been repeated. Instead the physician was elated since I had an AHI of 7. Anything above 5 qualifies for a CPAP. Of course, I also had no snoring, no apnea and O2 levels that were perfectly normal. I visited another specialist physician to have the results reviewed. He decided I had a severe breathing disorder that needed to be looked at by a Pulmonologist. The Pulmonologist told me the second expert did not know what he was talking about and nothing was wrong. Another physician told my wife, that since I had shallow breathing, I might die in my sleep. She was greatly alarmed and woke me up frequently during the night. Of course, months later that ignorant theory was debunked. By then I had bruised ribs. Finally a year later, a second sleep study was done with a home testing unit. The results were as close to perfect as possible. During the process I did a lot of research trying to understand sleep apnea and other related disorders. The whole field is more black magic than science. Clearly there are individuals with severe levels of sleep apnea who really can benefit from a CPAP. Then there are countless others like myself who are prescribed a CPAP needlessly.
โJul-23-2017 05:13 PM
โJul-23-2017 04:38 PM
โJul-23-2017 02:46 PM
rickst29 wrote:
You guys are in luck - me and the DW own both of the machines, Respironics and Resmed. And I'm pretty capable with electric things. ๐
- - - The efficiency issue - - -
Using a 12V regulator (Phillips "Respironics") or 24V converter (Resmed "Airsense") creates a big advantage over using the "120V Brick" with an Inverter: Efficiency!
With a typical "cheapo" Inverter, you will only get about 70% "output power" on 120V, in comparison to the 12VDC input power consumed. Following that power loss, the brick itself is only about 85% efficient. About 40% of your Trailer battery power gets wasted (85% times 70% = 59.5% efficient). In other words, you consume 40% more battery capacity to run the Inverter --> Power Brick Combination. That's why Inverters have fans on them: they're inefficient, creating a lot of waste heat.
In contrast, the DC-to-DC power supplies described here are about 93% efficient. No fans, maybe just a few small air holes. (My own Respironics power supply/regulator doesn't have any holes and stays cool - but I built it differently from my recommendation. It uses a "salvage" Vicor regulator module, list price > $200.)
- - - Respironics - - -
Running Respironcs "12V" from the 12V electrical system is fairly easy, and operates at 92-100% efficiency. You just need a much better plug and socket (instead of the "cigarette lighter" connectors). I use 15A twist locks, type ML1. They have the advantage of not pulling out when the sleeper rolls over. ๐
But you should probably use a Voltage Regulator as well. I did. (Trailer power varies from 11.9V up to 14.4V, depending on both the State-of-Charge and the operating mode of any active Converter/Charger device.) The CPAP machine doesn't face that much variance when running through the at-home "Brick"cConverter, and I feel that you should improve the regulation to meet or exceed the quality of the 120VAC Brick converter.
I'll SWAG this one to be suitable, although the seller's description doesn't make sense: http://www.ebay.com/itm/Waterproof-DC-8V-40V-To-DC-12V-10A-120W-Step-Down-Converter-Power-Regulator-.... (He says that it's "Step Down" Buck Converter, but I note that the Voltage Specification describes both "Boost" operation, 8-12V, and "Buck" operation, 13V-40V. You DO need both functions.)
Worst case - If this device isn't actually a dual function converter/regulator, you can use separate "Boost" and "Buck" Converters back to back, within your power supply project box: The first unit does "Boost" conversion to 24V (same as the Resmed converter/regulator), and the second unit does "Buck Conversion" back to regulated 12V. Efficiency will be a bit less, wasting 8-15% of the input power.
- - - Resmed - - -
This one is a lot more complicated than you might expect: Resmed uses a three-pin connector, with a specific requirement for Voltage and Resistance on the tiny pin "in the middle". Your first step, therefore, is to buy a cheap Resmed "Airsense-Compatible" 120VAC power supply from EBay, Amazon, or elsewhere: You're going to remove and use the output cord, throwing the rest of the power brick away.
You need 3 other parts (and a "project box" to hold the parts): A Regulating Boost Converter: 9V-12V in, 24V out, at least 120W (so it runs at half power or less, staying cool). We will use this one: http://www.ebay.com/itm/Waterproof-DC-12V-to-24V-10A-240W-Step-up-DC-DC-Converter-Regulator-Boost-in...
You also need a tiny step-down converter to create a 3.3V supply on Resmed's weird test wire. If you want to do surface-mount on a board, you can buy an individual chip to perform this job. I chose a cheap "tunable" Buck Converter with an input/output Voltage Display built-in (to help with tuning it properly), this one: http://www.ebay.com/itm/NEW-BUCK-STEP-DOWN-LM2596-POWER-CONVERTER-MODULE-DC-4-0-40-TO-1-3-37V-VOLTME...
+12V comes into the Converter from your high-current plug, creating 24V output. The 24V output goes into a "Y", with a "thicker" wire going into the +24V wire of the Resmed cord, and a thin +24V wire going into the small Buck Converter. Buck Converter Output must be routed through a 2.7K Ohm resistor, and then into the Resmed Sensor wire. (For example, the one I bought: http://www.ebay.com/itm/2-7K-Ohm-2w-2-Watts-1-Tolerance-Metal-Film-Resistor-10-Pieces/282286525128 The 24V ground is wired to the Resmed ground wire, and the 12V input ground wire goes back to your high-current plug.
As with Phillips/Respironics, this one should operate around 93% efficient, and it won't require require a fan. I'm waiting on parts and haven't actually built it yet, but I have high confidence that it will work great.
โJul-23-2017 10:23 AM
โJul-23-2017 09:53 AM
โJul-23-2017 07:54 AM
JimK-NY wrote:
It seems the entire sleep therapy industry is really just a sham.
I wonder if anyone has a sleep study and does not receive a recommendation for a CPAP.
โJul-23-2017 07:50 AM
Winnipeg wrote:
I used my CPAP as a good excuse to buy a Yamaha 1000 watt inverter.
โJul-23-2017 04:31 AM
โJul-22-2017 11:10 PM
ktmrfs wrote:MEXICOWANDERER wrote:
Even the $4,000.00 Respironics Dream Machine?
no, the respironics weren't a dream machine, resmed is the airsense and I love it.
But, from my experience, it's like so many things, use what works best for YOU.
the airsense 10 is working great for me, so I'm willing to accomidate the 24V supply wierdness.
โJul-22-2017 09:57 PM
โJul-20-2017 09:13 AM
MEXICOWANDERER wrote:Would that word be "OK"?
If my insurance tried to pawn off a 24 volt machine on me, my response would be simple the sole use of a two-letter word.
โJul-20-2017 08:30 AM
MEXICOWANDERER wrote:
Even the $4,000.00 Respironics Dream Machine?
โJul-19-2017 09:05 PM