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General Technical Chat / Re: Non-contact approach for measuring AC VAC/I and PF
« Last post by S. Petrukhin on Today at 12:33:35 pm »https://openenergymonitor.orgDo you trust Arduino firmware?
Recent Posts
2
Beginners / Re: What is H-type biasing?
« Last post by CaptDon on Today at 12:28:55 pm »Search Engine? Google? I've never heard of H-Type biasing? Guess we could all google it. Maybe H-Type is a fancy name for something we all knew all along? Like when the politically correct folks came up with the term 'Handi-Capable'.
3
Test Equipment / Re: Rigol ds1000z WFM file reverse engineering
« Last post by preamp.org on Today at 12:27:02 pm »What a mess 
Turns out that for every combination of Channel Number and Vertical Scale Setting you need two additional parameters to obtain the correct result: a scale factor and an offset. Fortunately both of them can be reconstructed from a single measurement, as long as you save it to both a WFM file and a CSV file. Then those parameters can be saved for later and applied to any subsequent WFM-only file conversions.
After building a little tool that takes the tedium out of all this, I just noticed that the two parameters are actually different for AC-coupled measurements
! So I'll have to take care of that, too.
Turns out that for every combination of Channel Number and Vertical Scale Setting you need two additional parameters to obtain the correct result: a scale factor and an offset. Fortunately both of them can be reconstructed from a single measurement, as long as you save it to both a WFM file and a CSV file. Then those parameters can be saved for later and applied to any subsequent WFM-only file conversions.
After building a little tool that takes the tedium out of all this, I just noticed that the two parameters are actually different for AC-coupled measurements
! So I'll have to take care of that, too.4
General Technical Chat / Re: Non-contact approach for measuring AC VAC/I and PF
« Last post by NiHaoMike on Today at 12:25:42 pm »5
Microcontrollers / Re: Can boxcar averaging cause rounding error?
« Last post by Circlotron on Today at 12:21:07 pm »@CirclotronSorry, don't understand the question. You'll have to be more specific.
Can you post the 16 values used in post #5?
John
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Beginners / Re: BT Audio decoder
« Last post by CaptDon on Today at 12:16:55 pm »Two things come to mind, 1, both sides of the speaker output are hot but phase inverted. You can't ground either speaker output lead. 2, the speaker audio level is far to high for the line level or mic level that the BlueTooth board may be expecting. Since the ground of the BT board and the ground of your other board are shared you may be able to run only ONE speaker wire (choose either speaker output terminal and run that to your L Audio In or perhaps L and R Audio In. You may have to build a two resistor audio level reduction also if the BT board is over driven.
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Metrology / Re: Symmetricom S200 Teardown/upgrade to S250
« Last post by DavidKo on Today at 12:16:01 pm »I speak only about GPS. 1PPS, 10MHz or NTP should work without upgrade. You only need to configure it, but I have never tried to use different source that GPS or ntp.
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Power/Renewable Energy/EV's / Re: Any use for old 3G flip-phone batteries?
« Last post by RoGeorge on Today at 12:12:10 pm »Depends of the battery, some become unusable, but most are just fine, except they only have about half of their nominal capacity. The oldest still in use I have is a Nokia from about 15 years ago, from when there were no touch screens, has physical dial pad buttons. Beeps to be recharged once a week.
I keep that phone because it has a very nice lap-timer, and a very easy to set egg-timer/alarm. Great to remind when to stop heating the food while loosing the track of time browsing the web. Another use of it is it can take audio notes with a press of a button, though recently I didn't use that very often.
In my use case, it happened that many of the Li-ion I have had for many years in storage, decided to swell almost all at once, in the same year. I suspect this is because I charged them to 4.2V and stored them fully charged. Since then, I only charge Li-ion to 3.7V before putting them in long term storage (long as in many months, or even years), and only charge them full if/when I need to power something.
What failed more often for me were the laptop batteries (the ones with typical 18650 round cells). They should last longer, have their own internal battery management chips and all, yet after a while they do not hold charge at all. I have had more luck with the single cells, flat and square batteries, from the old 3G mobile phones. Though, the mileage may vary with those, too.
I keep that phone because it has a very nice lap-timer, and a very easy to set egg-timer/alarm. Great to remind when to stop heating the food while loosing the track of time browsing the web. Another use of it is it can take audio notes with a press of a button, though recently I didn't use that very often.
In my use case, it happened that many of the Li-ion I have had for many years in storage, decided to swell almost all at once, in the same year. I suspect this is because I charged them to 4.2V and stored them fully charged. Since then, I only charge Li-ion to 3.7V before putting them in long term storage (long as in many months, or even years), and only charge them full if/when I need to power something.
What failed more often for me were the laptop batteries (the ones with typical 18650 round cells). They should last longer, have their own internal battery management chips and all, yet after a while they do not hold charge at all. I have had more luck with the single cells, flat and square batteries, from the old 3G mobile phones. Though, the mileage may vary with those, too.
9
Microcontrollers / Re: Can boxcar averaging cause rounding error?
« Last post by S. Petrukhin on Today at 12:11:07 pm »A right shift is a division with floor rounding. In order to correctly round you need to add half the divider to the start value.Code: [Select]value = (value+8)>>4
Is this true for negative values?
10
Beginners / Re: Raspberry Pi 3.5" Display Woes
« Last post by metrologist on Today at 12:09:00 pm »For the SD card, I was using Bookworm > Accessories > SD Card Copier. It got stuck for hours writing the second partition.
I made a clean install of Bullseye 64b and installed the LCD - and it works...
Now the problem is the windows run off the display.
WSJT-X installed but is not usable because most of the window is off the screen.
In Preferences, I changed the resolution to 640x480, the minimum, and that helped a little, but display is 320x480.
I tried some things like
xrandr -q
Then setup the panning itself :
xrandr --output DISPLAYNAME --mode 640x480 --panning 1920x1080
But xrandr does not tell me the display name so cant use step 2.
Then I tried to edit /boot/config.txt values to
overscan_left=24
overscan_right=24
Overscan_top=10
Overscan_bottom=24
Framebuffer_width=480
Framebuffer_height=320
Sdtv_mode=2
Sdtv_aspect=2
and that made it worse again.
I made a clean install of Bullseye 64b and installed the LCD - and it works...
Now the problem is the windows run off the display.
WSJT-X installed but is not usable because most of the window is off the screen.
In Preferences, I changed the resolution to 640x480, the minimum, and that helped a little, but display is 320x480.
I tried some things like
xrandr -q
Then setup the panning itself :
xrandr --output DISPLAYNAME --mode 640x480 --panning 1920x1080
But xrandr does not tell me the display name so cant use step 2.
Then I tried to edit /boot/config.txt values to
overscan_left=24
overscan_right=24
Overscan_top=10
Overscan_bottom=24
Framebuffer_width=480
Framebuffer_height=320
Sdtv_mode=2
Sdtv_aspect=2
and that made it worse again.