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Re: VBAT resistor voltage divider, polynomial fitting, VBAT sampling
On 2020-07-16 08:05:-0700, you wrote:
FYI - In the current source code the internal on-chip vbat divider is always enabled. <SNIP>Well, if it is always on, then the circuit draw 4V / 100K ohms = 40 e-6A = 40 uA. If the battery is a 400 mAh battery, then it will take 10 000 hours to drain the battery. Is that a concern? With the resistor voltage divider in place of the diode, the numbers are roughly the same, so battery drain there is not a problem either. Feel free to correct my estimates...I have been known to miss a decimal point or two when I do this in my head. -- 72/73 de Rich NE1EE On the banks of the Piscataqua |
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Re: VBAT resistor voltage divider, polynomial fitting, VBAT sampling
On 2020-07-16 06:56:-0700, you wrote:
The Vbat, at least what I see in the sources for H4, is being sampled such the Vbat voltage divided by 2 (internal on-chip divider, most probably disconnected when not in use) is converted via the ADC channel 17. There are no external dividers needed.Skipping over "most probably" as an excellent example of what was not shared in the early days... We come to "There are no external dividers needed." But...again, according to the early design...the batteries peaked at 4.2+V, and the VBAT signal is spec'd at a max of 3.6V. It can go slightly higher, but not by design spec. So the original designer included a diode in the path to VBAT. The idea was that there would be a roughly 0.6V drop across the diode, and that would drop the 4.2 to 3.6. So the diode was taking the role of a voltage divider. My concerns were a) the diode was operating in an unstable region, due to the low current through it. Why the low current? Because the VBAT sampling circuit used a 100K resistor to sample across. (Actually 2 50K, but the diode sees 100K). b) if the diode is not allowed to settle, then its voltage drop is not predictable. In higher current circuits, using a diode in this fashion is fine. c) the clue to the design flaws is in the fact (as I understood it) that VBAT was sample 20+ times, and the results averaged. d) the whole reporting of the voltage to 4 significant figures is pointless. All we really care about it is estimated battery charge to the nearest 20%, right? The rather unusually high noise in the vbat data readings I presented in my other post could be caused by something missing in the H4 code, ie. a small delay should be inserted after activating the divider - before reading the vbat, or something like that..Well...exactly the original point I made...and I am not saying that I am "correct", only that I surfaced a reasonable question, and was snubbed by people who said that they had not read the manual. It's pretty standard to take into account all the timing delays in an ADC circuit. None of them are instantaneous. And this problem is worse if my suspicion about the unstable diode response is valid. Resistors won't have that instability. These are just discussion points...not everyone will see the situation in the same light...or need...after all, we have some estimate of battery voltage now, right? -- 72/73 de Rich NE1EE On the banks of the Piscataqua |
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Re: Protective Case for H4
That is correct.
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Darrell Sent from my over-rated IPhone 7 Plus. Any Mis-spellings or grammar errors are due to my IPhone auto correct feature. On Jul 16, 2020, at 15:52, David Webb <kb1pvh@...> wrote: |
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My NanoVNA is overheating
NanoVNA-H V3.4
DiSlord 0.9.3.4 firmware I performed and open calibration only with no cables. The temperature in the room is 80 degrees Fahrenheit. First picture was taken when device was turned on. Second picture was taken 6 minutes after turning on. Third picture was taken 15 minutes after turning on. If I put a bag of frozen vegetables on top of the device it works great, it is perfectly stable. If I issue a threshold 200000000 command it overheats more slowly. I bought the device in February and it worked well in the cooler months. Thinking about adding a heat sink somewhere, but not sure where. Any ideas? -- Gary AG7TH |
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Re: Protective Case for H4
No 3-D printer here. So I modified the very nice box my H-4 was shipped in. I provided some large open cell rigid packing material to hold items in place. The small bottle holds the calibration pieces. This is secure and quick, cosmetic touches lacking.
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Took about an hour to complete. KEoZUW John On Jul 16, 2020, at 3:52 PM, David Webb <kb1pvh@...> wrote: |
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Re: Protective Case for H4
That is cool.
1. Do you have pics to share to show? 2. Are you going to make any to sell, for those of us without 3D printers? (Yes, there are still some of us out there)... [image: photo] *Bob Willey* K3RLW (410) 251-8960 | K3RLW@... 5161 Ocean Gateway, Trappe Maryland 21673-2023 USA <> <> <> <> On Thu, Jul 16, 2020 at 9:24 AM Darrell Carothers <rescuemedic1@...> wrote: Just FYI, I designed a protective case for the H4. It is a bit oversized |
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Re: Protective Case for H4
Looks to be this
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Dave-KB1PVH Sent from my Galaxy S9 On Thu, Jul 16, 2020, 4:46 PM Rick Commo <rick.commo@...> wrote:
What¡¯s the thingiverse number? |
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Re: Protective Case for H4
I just don¡¯t have exact measurements to verify the fitting for the other models.
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Sent from my over-rated IPhone 7 Plus. Any Mis-spellings or grammar errors are due to my IPhone auto correct feature. On Jul 16, 2020, at 10:33, K4YQ - Steve <K4YQ@...> wrote: |
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Re: nanoVNA Saver exports s2p files with S11 = S21
#nanovna-saver
Git Hub shows 0.0.3.6-rc2 is the latest version of NanoVNA Saver
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Should I be staying with the 0.0.3 version? or moving to the 0.3.3.6 version? KEoZUW John On Jul 15, 2020, at 1:44 PM, Holger M¨¹ller <dg5dbh@...> wrote: |
Rich NE1EE
Darrell Carothers
John Nicholas
Bob Willey K3RLW
David Webb