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I've had repeated power outages over the last few nights and i was already making this device for my RV to be able to go off grid. needless to say i lost sight of the project and since the last few nights of horrible sleep i revisited this effort and found that i could get the resmeds10 to work without the heated reservoir and climate line tube as well as complaining about the plug being not plugged incorrectly i found this post. adding the 2.7 k resistor fixed the issue and I'm so grateful for your post! TY TY TY!!! the last 2 nights I've woken up up many times when the UPS's that I've been cycling through the bedroom ran out of power and as you may know, waking up a cpap powered off is like running out of air while diving! last thing is this, do I Need to add the CAP to the formula as I've got the 12/24 x 10 amp transformer and the 3.3 volts, the resistor but i noticed you mentioned a cap. currently i don't have that and wanted to know if i need it as i don't want to screw anything up? Thank you again, this post fixed my experiment and will allow me to sleep with what i hope is only one car battery by the bed!


Thank you so much

Brian

THAT OUTPUT CAPACITOR IS NOT NECESSARY.

In my first build, that output capacitor was intended to add a tiny bit of additional "smoothing" for the 24-VDC output of the boosting regulator. It turns out to be unnecessary, because the boosting regulator's internal capacitance (on the output) is more than sufficient by itself.

That capacitor was only about 10% effective anyway, because it was in-line along the 24v output path. A more effective and traditional design would have connected the capacitor to common Ground, through a large resistor.

I added a 12v to 24v directly to the power cable after the original transformer. It seems the 3.3v was produced automatically by the 24v going back to the transformer. I can measure all the voltages correctly on the power pin. (ignoring whether this is safe/appropriate). The resmed machine blinks but does not approve of this setup (even though it should have the inline resister. I guess I need to complete disconnect the transformer and provide my own 3.3? Strange. Thoughts?