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Will a 20 volt DC converter work with the S9?
Hi toller,
WELCOME! to the forum.!
Much success to you as you continue your CPAP therapy.
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(02-27-2016, 04:01 PM)eseedhouse Wrote:
(02-27-2016, 07:20 AM)OMyMyOHellYes Wrote:
(02-27-2016, 06:21 AM)pholynyk Wrote: Does anybody know the function of that third pin, the skinny one?

So ResMed can suck more money out of their customers.

Well, this connector is a standard one and Resmed doesn't make it themselves, so it must have some other use. I'm not saying that they don't want to suck customers our of their money, just that it is not a bespoke one of a kind connector.

Usually in 3 pin connectors the third one is connected to ground. See yer standard 3 pin wall plug for instance.

Please read more carefully.

Nobody said it was a unique connector.

It is how they have programmed their machines to pick up some mystery signal off that third pin from their proprietary DC DC "converter" in order to work. All so you can't go to Mouser Electric and buy the connector and just hook up a 24 V battery to run the machine.

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I've found that the A10 will run from a +24 volt power supply when the center pin is connected to +3.3 volts thru a 2.7k ohm resistor. I use a +3.3 volt three-terminal voltage regulator fed from the +24 volt power supply. The resistor functions as a pull-up resistor to +3.3 volts and tells the cpap the power rating of the supply. I've tested this on two units.

I realize that this discussion is about the S9 but it's possible this will work on the S9 too.

Someone could measure the third pin of an S9 DC to DC converter or a S9 AC supply with a dc voltmeter. If it measures +3.3 volts with respect to common, then it's probably using the same scenario as the A10.

Because the series resistor provides current limiting protection for the cpap, I don't think it would be too risky to try.


Just my personal opinion. My posts are not medical advice or a statement of fact. Please consult a qualified physician or other qualified medical personnel. Please comply with all applicable laws, codes, regulations, and protocols.
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