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by Paul Hutch
Wed Oct 07, 2020 3:38 pm
Forum: General discussion
Topic: 2 more SD cards
Replies: 27
Views: 1181

Re: 2 more SD cards

Waking this one up for a tangent: https://lab.ktemkin.com/post/why-is-usb3-harder/ I'm not going to use USB3 for disk after reading this. Anyone who does not have background in electrical engineering, especially high speed data transmission, should probably NOT read that article. Seeing how the sau...
by Paul Hutch
Sat Oct 03, 2020 12:55 pm
Forum: General discussion
Topic: Poor Man's Pi Safe Backup Supply (UPS)
Replies: 51
Views: 3866

Re: Poor Man's Pi Safe Backup Supply (UPS)

LTolledo wrote:
Sat Oct 03, 2020 9:48 am
4.2v is enough for safe shutdown? :shock:
Based on a quick scan of the schematic it's even worse, 4.2V - the diode Vf which is 0.32Vmax @ 0.1A, 0.45Vmax @ 1A.
by Paul Hutch
Thu Aug 27, 2020 2:09 pm
Forum: Advanced users
Topic: Industrial use
Replies: 9
Views: 455

Re: Industrial use

If you want something that is reliable the you need to take a look at a PLC. This product are designed for task like this. And as a additional you could also implement an additional faile save for your tank. For example a temperature fuse, if the temperature runs away, at a certain temperature the ...
by Paul Hutch
Thu Aug 27, 2020 1:52 pm
Forum: Advanced users
Topic: Raspberry 3+ wifi antenna
Replies: 17
Views: 30027

Re: Raspberry 3+ wifi antenna

You'll want to get that tested and approved before you use it - modifying radio devices like this is actually illegal and not a subject allowed to be discussed here as such. UncleJoe shows as being in the USA so he does not need to get it certified before personal use on his own property. If the sy...
by Paul Hutch
Wed Aug 12, 2020 12:40 pm
Forum: Python
Topic: Clear GPIO on program crash
Replies: 5
Views: 208

Re: Clear GPIO on program crash

In an application where I need to recover from untrappable crashes I've done it by having a monitor program launch the application program with subprocess.Popen(). Then the monitor program periodically calls the poll() method to see if the application is still running. https://docs.python.org/3.5/li...
by Paul Hutch
Thu Aug 06, 2020 6:10 pm
Forum: General discussion
Topic: A bunch of solar usb battery packs
Replies: 22
Views: 866

Re: A bunch of solar usb battery packs

Dimensionally, that's nonsense. 15W == 15J/s, 15W/h == (15/3600)J/(s^2). The two are not the same. @Heydt's statment of "15W or 15Wh/hr. 15Wh/hr * 24 hr = 360Wh" is absolutely correct other than the mix of "h" and "hr" and it even makes sense if read out aloud. Yours is incorrect but I love trying ...
by Paul Hutch
Thu Aug 06, 2020 2:30 pm
Forum: Other projects
Topic: Peak Tech 8005 IOT Sound Level Meter
Replies: 4
Views: 277

Re: Peak Tech 8005 IOT Sound Level Meter

You need to ask the manufacturer for a Linux compatible driver for ARM processors and communications protocol information. AFAICT, they only provide drivers for Windows and I didn't see any protocol info. It's not unusual for a manufacturer to have a Linux driver that they only supply on request do ...
by Paul Hutch
Thu Aug 06, 2020 2:23 pm
Forum: General discussion
Topic: A bunch of solar usb battery packs
Replies: 22
Views: 866

Re: A bunch of solar usb battery packs

5v time average current times the time interval. If you want to be (engineering) conservative, use the nominal max current spec of 3A. Doing that, you are drawing 15W or 15Wh/hr. 15Wh/hr * 24 hr = 360Wh. The units you used are a not quite correct causing some of the confusion, at least for me. Watt...
by Paul Hutch
Tue Aug 04, 2020 12:29 pm
Forum: Python
Topic: Do something after 3 button presses
Replies: 10
Views: 421

Re: Do something after 3 button presses

I'd be very surprised if any switch, even homemade, had a bounce time of more than 0.2 seconds. So I suspect three switches pressed sequentially in 2 seconds should be workable even with your particular switches. When I tried the debouncing in gpiozero a couple years ago I found it to be woefully in...
by Paul Hutch
Mon Aug 03, 2020 2:59 pm
Forum: Python
Topic: Do something after 3 button presses
Replies: 10
Views: 421

Re: Do something after 3 button presses

Here's a quick untested translation into Python of rpdom's pseudo-code. I assume buttons are True when on, if False when on, add "not" to the button comparisons, e.g. if not button_1:. timestamp = 0 stepno = 0 if button_1: timestamp = time.perf_counter() stepno = 1 if button_2: if stepno == 1 and ti...
by Paul Hutch
Fri Jul 31, 2020 3:19 pm
Forum: Astro Pi
Topic: Odd Temperature readings from SenseHat... not heat related
Replies: 4
Views: 670

Re: Odd Temperature readings from SenseHat... not heat related

Be aware that because the temperature and %RH sensors on a SenseHat are located on a PCB with heat generating components and mounted close to a very hot CPU the readings are very different than ambient. On my unit running here the temperature reads about 17°C/30°F higher than ambient when the CPU is...
by Paul Hutch
Tue Jul 28, 2020 1:31 pm
Forum: Python
Topic: Import Error: You must be root
Replies: 9
Views: 2761

Re: Import Error: You must be root

From the README on the main page: Known limitations: ... ... ... To avoid depending on X, the Linux parts reads raw device files (/dev/input/input*) but this requires root. ... ... When I went looking for a cross platform keyboard and text screen handling library for Python last year, I ended up cho...
by Paul Hutch
Tue Jul 28, 2020 1:13 pm
Forum: Advanced users
Topic: Is hot plugging a microSD electrically safe?
Replies: 13
Views: 810

Re: Is hot plugging a microSD electrically safe?

The power connections on a microSD card are longer to guarantee power is applied first so that there are no electrical problems when hot swapping.
by Paul Hutch
Mon Jul 27, 2020 1:19 pm
Forum: General discussion
Topic: Price and size of a Raspberry Pi 3 or 4
Replies: 38
Views: 2100

Re: Price and size of a Raspberry Pi 3 or 4

Both of these statements are false! I cannot find a RPi 3 or 4, new for $35 on any of the reseller sites. They are often double that price. Most credit cards are 54mm x 86mm while my newest Pi is 70mm x 94mm. From the "Products" tab above, I selected "Raspberry Pi 3 Model B+" then "Buy now" and ope...
by Paul Hutch
Wed Jul 22, 2020 1:50 pm
Forum: General discussion
Topic: 2 more SD cards
Replies: 27
Views: 1181

Re: 2 more SD cards

USB 2.0 and higher are faster than SPI. With wire connections SPI can usually only achieve less than 10 Mbps, USB 2.0 can do 480 Mbps.
by Paul Hutch
Wed Jul 22, 2020 1:38 pm
Forum: General discussion
Topic: FCC Part 15 Subpart B compliance
Replies: 3
Views: 224

Re: FCC Part 15 Subpart B compliance

Part C (intentional radiator) certification includes all of the limitations of part B (unintentional radiator) verification, so no separate part B verification is needed for intentional radiators. I just checked the certification/verification reports for the products I've had certified or verified i...
by Paul Hutch
Wed Jul 22, 2020 1:19 pm
Forum: General discussion
Topic: 2 more SD cards
Replies: 27
Views: 1181

Re: 2 more SD cards

You can use SDIO for a 2nd SD card if you drop the WiFi: https://hackaday.com/2017/08/05/add-a-second-sd-card-to-the-pi-zero/ But apparently the Raspberry 4 can add a 2nd SD card without disabling the WiFi. So again my question is not if you can add a 2nd SD card, because you can. But can you add a...
by Paul Hutch
Mon Jul 13, 2020 10:40 pm
Forum: General discussion
Topic: How do you know if you need to add a cooling component for your Pi4?
Replies: 15
Views: 797

Re: How do you know if you need to add a cooling component for your Pi4?

According to "your" method, my mobile phone requires a heatsink... That's only because you set a value for Td that is too low. If you set it high enough you can even create flames. ;) The formulas from LTolledo seem useful to me. Of course to use them effectively you need to determine an appropriat...
by Paul Hutch
Mon Jul 13, 2020 10:26 pm
Forum: Advanced users
Topic: Connect serial device to RPi 3
Replies: 53
Views: 2080

Re: Connect serial device to RPi 3

I'm trying to connect a W800 X10 command receiver to the receive pin of UART0 on a Rpi. The W800 signals with 8 bit data, no parity, 1 stop bit at 4,800 baud. The signal level is 3.3 V. http://www.wgldesigns.com/w800.html (Note: I am not using the USB version of this receiver, but the older RS232 v...
by Paul Hutch
Fri Jul 10, 2020 1:01 pm
Forum: Python
Topic: How Do I Log The CPU Temperature Whilst Factoring Numbers?
Replies: 2
Views: 271

Re: How Do I Log The CPU Temperature Whilst Factoring Numbers?

For code simplicity and to facilitate reuse, I use two scripts that run simultaneously when I want to monitor CPU temperature while executing other code. I start the system monitor logging program in a separate terminal or by setting it to run in the background with &. Then I start the application/s...
by Paul Hutch
Thu Jul 09, 2020 2:49 pm
Forum: General discussion
Topic: Finances - programs for Raspberry
Replies: 4
Views: 276

Re: Finances - programs for Raspberry

Another Quicken alternative is GnuCash which is in the repository. https://www.gnucash.org/ It's been awhile since I tried either program but last I checked they were both missing the one essential feature that keeps me locked into Quicken. A calendar display that projects account balance based on a...
by Paul Hutch
Thu Jul 09, 2020 2:27 pm
Forum: General discussion
Topic: Battery module for Raspberry PI 3b
Replies: 3
Views: 176

Re: Battery module for Raspberry PI 3b

3.7V and 560mAH ~= 2 WH (3.7 * 0.56) which ~= the typical bare-board active current consumption of a Pi 3B (5 * 0.4). https://www.raspberrypi.org/documentation/faqs/#pi-power The conversion from ~3.7V to 5V will waste some of the power available so that battery would run a Pi 3B for less than 1 hour...
by Paul Hutch
Thu Jul 09, 2020 1:54 pm
Forum: Python
Topic: simplekml tracks not pinpoints
Replies: 6
Views: 313

Re: simplekml tracks not pinpoints

In case you decide to use the roll your own from base XML route like i did, here's a handy KML reference document. https://developers.google.com/kml/documentation/kmlreference BTW - there are a lot of KML features that no program, including Google Earth, lets you implement in a GUI. So for all of my...
by Paul Hutch
Wed Jul 08, 2020 1:33 pm
Forum: General discussion
Topic: Best practice for generating an image using Raspberry OS
Replies: 11
Views: 399

Re: Best practice for generating an image using Raspberry OS

Dear RPI-fellows, My problem in a few words: I've generated an image on a 2GB RPI4 and put it to a 4GB RPI4. However, then the execution time of the code increased around a factor of 5. I did the following tests (Basically there is an old RPI4-2GB and an old RPI4-4GB as well as a new RPI4-4GBb that...

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