CPAP on a battery

[LoBattery]

I'll have those answers soon for a Autosense 10. My cable just came in. But, I'm down to one machine right now and will get a backup in a week to be safe. Stuff happens. At the very least you will need a 3.3V regulator and a 2.7K resistor to drive that third center pin. It seems pretty likely there is communication between the units. Believe I have an easy work around for that.

wolfnrose..... I'm glad you are taking all this shit and not me. I run my cpap on solar and it even shuts off in the morning automatically. I'm the king of inverters . I got a little 100W RIDGID and it won't even power the cpap when it is turned off. It just continuously goes on an off. Many small inverters do that on this type of load. I use a 400W inverter with fans disconnected for lower power use. This actually uses less power than a 200W unit. MSW won't hurt this. I buy my inverters broken and actually remove the H bridge section that makes the MSW. I run almost all of my electronics on straight 140V DC. That is all the switching power supplies care about anyway.

[wolfnrose]

Thanks for the information... do you have the link to the apnea board posting regarding prototype? Also, was this attempted by people who have electronic knowledge, or folks just hacking at it? From what I can tell it strongly looks like it's a simple voltage splitter to represent supply capacity, but even adding a $1 Arduino for digital signaling would not be a big issue...

Beyond academic interest (not to be ignored), I also just find a 17 x markup offensive on principle... I'm happy to support reasonable pricings but $200 plastic masks and $90 power supplies is just being abusive of people who need CPAP...

[palerider]

FYI, for other crazy people wanting to experiment with DIY 12V to 24V adapter: ...

There was a recent thread here with someone who wanted to build a converter, including figuring out the third pin characteristics. After getting a disheartening response, he deleted his posts and moved the discussion to apneaboard where a few others helped design a board.

the idiot and his hugely complicated bizzare setup was supplanted by a resistor.

[LoBattery]

Look this patent up, Pub. No.: US 2014/0366876 A1. It can communicate other than sensing the pullup resistor. Amazed the actually specify the 2.7K resistor from 3.3V in the patent, confirmed with testing. Whether it has to is another question. If communication is necessary with the power pack, powering the power pack on the DC side ( splice or extend the power cable) will likely do it. Agree it wouldn't be hard to decipher the onewire communications. Actually, the power pack is a deal for $90 considering it can drop the battery requirements in half vs the double conversion. I hate batteries.

Proprietary? There is nothing proprietary in China. I went to a Beijing trade show and was going to import a product. They sent me three samples and I found a software bug. They had me contact the software developer in Hong Kong. They at least knew who buttered the bread. Turned out that company was already partially owned by a US firm. Nasty letters ensued. Everything is for sale in China, they make copies of copies.

Never assume anything.

[wolfnrose]

I've heard different resistive values for the signal pin tossed around (47K above, 3.9K elsewhere), but in the interests of making this crazy-simple... assuming we trust the 24V supply, could the "signal" lead be handled by a simple resistor splitter feeding a "sense" resistor? I'm more hacker than serious electronic designer, so... is this "magic" or just "magic smoke"???

(Can't figure out how to attach images here, so pardon my ASCII art...)

G 3.3V 24V outputs
| | |
| < |
| > 3.9K |
| < |
| | |
| 1.5K | 100K |
|---v^v^v--|---v^v^v-|
| |
| |
G in 24V in

[palerider]

I've heard different resistive values for the signal pin tossed around (47K above, 3.9K elsewhere), but in the interests of making this crazy-simple... assuming we trust the 24V supply, could the "signal" lead be handled by a simple resistor splitter feeding a "sense" resistor? I'm more hacker than serious electronic designer, so... is this "magic" or just "magic smoke"???

(Can't figure out how to attach images here, so pardon my ASCII art...)

Code: Select all

G      3.3V   24V   outputs
|               |            |
|               <            |
|               > 3.9K     |
|               <             |
|               |             |
|    1.5K    |   100K   |
|---v^v^v--|---v^v^v-|
|                             |
|                             |
G in                      24V in

you have to put stuff like that in a code block to have even a chance of readability.

and yes, a 47k resistor to 24v is said to work just fine.

[LoBattery]

voltage value may be detected by the analog to digital con
verter 608 . A protection resistor 612 may be utilized to protect
the A-D converter.
[0055] For example, if the pull-up resistor represents the
type of power supply, a detection of 3.9 K ohms may be
interpreted by a master controller that the power supply is an
in?nite supply (mains). A detection of 2.7K ohms may be
interpreted as a 90 Watt power supply. A detection of 1.8K
ohms may be interpreted as a 60 Watt power supply. A detec
tion of 1.0K ohms may be interpreted as a 30 Watt power
supply. Other voltage levels and coding schemes may also be
utilized to code information about the power supply unit in
this analog manner. Optionally, digital messaging may also
be utilized to detect information about the power supply unit
or other components of the bus.

It may recognize or it may not depending on their acceptance values.

[LoBattery]

I keep wondering about the removal of those posts. Many boards limit the time you can do that. Certainly a feature some should take advantage of. Did Resmed threaten legal action? Doubt it as they made all the details public themselves. Did he get pissed of at the boards comments and pull the details? That certainly is possible. Did he get a little to cavalier and damage his machine? Entirely possible, along with the thought that others might do the same thing an he would be blamed. I answered a question on a technical board. I said "use a 10-15K ohm resistor." He came back the next day really pissed off at me after it went up in smoke. Said that just to be safe he used a 15 ohm resistor. To this day I don't actually know what english is correct. It taught me to be very careful with wording when dealing wit people of limited technical experience. I now say 10K-15K to eliminate confusion.

As far as the voltage divider, I would definitely never use a single resistor as that could damage the chip from over voltage. That 1.5K resistor in the divider and say 5K in parallel with it for the test, it now looks like a 1.1K resistor dropping the read voltage by 23%. So it might work or not and it may not be repeatable by others. Reducing the divider numbers by 3 or 4 would get you closer.

[palerider]

I keep wondering about the removal of those posts. Many boards limit the time you can do that. Certainly a feature some should take advantage of. Did Resmed threaten legal action? Doubt it as they made all the details public themselves. Did he get pissed of at the boards comments and pull the details? That certainly is possible. Did he get a little to cavalier and damage his machine? Entirely possible, along with the thought that others might do the same thing an he would be blamed. I answered a question on a technical board. I said "use a 10-15K ohm resistor." He came back the next day really pissed off at me after it went up in smoke. Said that just to be safe he used a 15 ohm resistor. To this day I don't actually know what english is correct. It taught me to be very careful with wording when dealing wit people of limited technical experience. I now say 10K-15K to eliminate confusion.

As far as the voltage divider, I would definitely never use a single resistor as that could damage the chip from over voltage. That 1.5K resistor in the divider and say 5K in parallel with it for the test, it now looks like a 1.1K resistor dropping the read voltage by 23%. So it might work or not and it may not be repeatable by others. Reducing the divider numbers by 3 or 4 would get you closer.

go home, you're drunk and not making any sense at all.

[LoBattery]

go home, you're drunk and not making any sense at all.

Of course I don't make any sense to you. You have no idea what you are doing.

[CapnLoki]

go home, you're drunk and not making any sense at all.

Of course I don't make any sense to you. You have no idea what you are doing.

Now I remember what drove verbatim around the bend!

[palerider]

go home, you're drunk and not making any sense at all.

Of course I don't make any sense to you. You have no idea what you are doing.

Now I remember what drove verbatim around the bend!

verbatim was an idiot. his "circuit design" was stupid, if you follow through the discussion "over there" you'll find people that have successfully made a 12-24 boost converter and powered their resmeds with nothing more than a resistor added.... or so they said.

take that for what it's worth.

[palerider]

go home, you're drunk and not making any sense at all.

Of course I don't make any sense to you. You have no idea what you are doing.

neither, it's clear, do you.

[TheSnoringMan]

FYI, for other crazy people wanting to experiment with DIY 12V to 24V adapter:

$2.64 delivered, 150W boost converter:

http://www.aliexpress.com/item/150W-DC- ... 47286.html

$3.99 delivered, 100W boost converter with LED voltage displays (best if NOT using humidifier/heater):

https://www.aliexpress.com/item/DC-DC-1 ... 55003.html

I'll SWAG these to be unsuitable unless a big output "filter capacitor" is added. The one with LED bears two 47pf Capacitors. They're definitely isolators, and not filters. The Resmed AC/DC PSU has a 560uF electrolytic capacitor (big and slow) along side the small, fast isolating capacitors. Also, your Boosters appear to adjust a single ratio - and a voltage change, which might be anything between "bulk charging" 14.4V down to 12.6V "50% SOC discharging", might be result in fluctuating output Voltage from your boards. Neither Product description includes the magic word "Regulator".

Now I just need the plugs... I *think* it's a 7.4mmx5mm (gotta check when at CPAP), but if so here's a wired plug with (yes!) three wires... which I suspect are intended for just the 20-47K resistor bridging we've been discussing...
https://www.aliexpress.com/item/2015-DC ... 81485.html
If this works, it's literally $5 to recreate the $85 adapter.

I'll SWAG the Dell cord to also be "inadequate". I'm not a brain surgeon or licensed engineer, but the Resmed Inductors have 2x the radius, more length, and a lot more mass: and there's TWO of them. IIUC, Resmed is running both the electronics (finicky) and the DC motor (brutually reactive, asymmetrical square wave) from the same 24V supply line. The inductors (if I may wave my hands without supporting math) might be there to help "smooth things out"... above and beyond the slow but big "Smoothing" already imposed by the large capacitor.

I'm interested! But before I would present a list of specific parts, I would verify that it runs a Resmed A10 for many hours without letting magic blue smoke escape - from either the Resmed, or from itself. Are you going to do that?

[palerider]

and the DC motor (brutually reactive, asymmetrical square wave)

Only, it's not, not even close... which does tend to call your other "SWAG"s into question.