(06-10-2016 11:39 AM)TiredInSoCal Wrote: I don't know much about electronics, but would love to buy a cable or maybe a kit of the supplies + instructions from one of you when this is ready
I don't think anyone here is considering "commercializing" this.
The goal, I think, is to list the parts that are needed, and to draw the diagram, and after that, it's up to you to solder them together property.
Have you ever soldered resistors, capacitors, and transistors together?
(06-10-2016 10:10 PM)justMongo Wrote: These are split down the middle and can be snapped around an existing wire or cable.
The ferrite choke goes close to the EMI source one wishes to suppress. It keep the distal wire/cable from acting as an antenna.
Thanks for that answer.
I'm really confused about why we need/want these ferrite beads.
I understand your words, which are that:
a) Any EMI generated by the 3.3 volt regulator with pull-up resistor can be "suppressed", and,
b) The few feet of wire acts as an antenna.
Both statements confuse me for slightly different reasons:
1. Does this circuit GENERATE EMI? I don't see where, or how. EMI means oscillation, and this is a DC circuit, so, where is the oscillation?
2. Even so, I do agree that a length of wire is an antenna to radio waves that happen upon it; but why do we care if the wire acts as an antenna?
Since the CPAP machine is basically a fancy fan, with a bit of electronics (probably far less than what it in a typical cellphone), why do we even CARE if the wire acts as an antenna?
The ResMed motor must generate more "noise" than anything, and it can't be "that" sensitive to AM/FM signals picked up by the wire on a 24VDC line, can it?
So, fundamentally, I would worry more about a lightning strike on the equipment than the EMI it generates or receives. But, that's just because I'm confused why we care about the puny amount of radio energy induced in the wires, or about the puny amount of oscillation in the sense circuit.
(06-10-2016 10:10 PM)justMongo Wrote: 1/4, 1/2, 3/8 are the diameters of cable they will snap closed around.
Thanks for that explanation.
I appreciate your patience.
BTW, I would like to correctly attribute the diagram. Did both Mongo and Steve design and build the thing? Who designed it? Who built it?
I just want to get the attribution correct.
To add further reference value to this thread, here is an earlier version (apparently) of the ResMed patent application:
- Patent application title: POWER MANAGEMENT IN RESPIRATORY TREATMENT APPARATUS
- Patent application number: 20110162647
- Respiratory method or device means for mixing treating agent with respiratory gas control means responsive to condition other than user's airway pressure
A key paragraph, with respect to the circuit depicted in the OP, is:
Patent-application-20110162647 Wrote: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 infinite 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 detection of 1.0K ohms may be interpreted as a 30 Watt power supply.
It's hard to summarize the patent because of the 97 separate lawyer-included claims, but what the patent does is allow fundamentally two "claims" that we actually care about when designing our own tent camping battery based power supply for the ResMed A10:
- The analog sense circuitry senses the pull-up resistor value
- Hence, it "knows" the power supply's ability to source power
- At least with the granularity of (a) Mains, (b) 90W, © 60W, and (d) 30W (at roughly 30Watts per 900K Ohms)
- The machine prioritizes gas flow over accessories (such as heaters and humidifiers)
- For example, the controller synchronizes de-powering of the heater during an increase in a speed of the blower
- Fundamentally, that means the accessories are powered during exhalation, and de-powered during inhalation
In addition, we get some insight into how ResMed may be organizing their power and communication bus inside the A10 when they claim:
Patent-application-20110162647 Wrote:In some embodiments, the system components may be coupled together for electrical communication by a common system bus...For example, the system bus system may be implemented with a power supply line (e.g., a 24 volt supply line) a communication line (e.g., a 3.3 volt VCC logic high level) and a ground line.
Fundamentally, that implies (but does not decree) that the 24VDC is used internally to power the components while the 3.3VDC reference voltage is used to indicate a "logic 1" on the communication line.
Where that matters greatly is if someone tries to connect "just" a 24VDC power supply to the ResMed A10, the communications line will have a "logic 0", which, almost certainly would prevent the machine from running.
So, our main goal is simply to provide two things to the ResMed A10 in our tent-camping power supply:
- A logic 1 on the communication line (across a 2.7K Ohm pull-up resistor)
- A well-regulated 24VDC on the system bus (e.g., two nominally 12VDC batteries in series)