Go to advanced search

by Paul Hutch
Thu Oct 10, 2019 8:43 pm
Forum: General discussion
Topic: Raspberry Pi 3 B+ supply?
Replies: 8
Views: 227

Re: Raspberry Pi 3 B+ supply?

Wow there does appear to be a big shortage of 3B+ in North America. Adafruit is limiting it to 2 per customer and Vilros is limiting it to 1. Newark, Allied, and Arrow are all out of stock. Newark, who often has thousands in stock, says 20 expected November 7th and more not coming until February.
by Paul Hutch
Fri Oct 04, 2019 6:13 pm
Forum: General discussion
Topic: power cut while logging to txt file
Replies: 5
Views: 215

Re: power cut while logging to txt file

If you are writing the file via Python, then adding the buffer=1 option to the open command will help. The default buffer setting doesn't write the data out until the buffer is full, typically 4096 or 8192 bytes, or the file is closed.

https://docs.python.org/3/library/functions.html#open
by Paul Hutch
Wed Oct 02, 2019 3:33 am
Forum: Advanced users
Topic: Power demands
Replies: 7
Views: 362

Re: Power demands

I am using a USB 3.1 cable retrofitted and shortened for this application. Check the gauge of the wire, many USB 3.1 cables have thin power conductors (26 AWG or smaller). A 0.5m 26AWG cable will drop 0.4V @ 3A which with a nominal 5V supply will definitely be a problem. Even a 24AWG 0.5m cable wil...
by Paul Hutch
Tue Oct 01, 2019 4:38 pm
Forum: Advanced users
Topic: Power demands
Replies: 7
Views: 362

Re: Power demands

Even the most power hungry Raspberry Pi setup should use less than 20 Watts. So if the RavPower USB power supply gives 20W per port you should only need one port. (Pi4 power adapter is 15.3W https://www.raspberrypi.org/products/type-c-power-supply/). What length and gauge of wire are you using for p...
by Paul Hutch
Thu Sep 19, 2019 10:20 am
Forum: General discussion
Topic: Low voltage warning even though gpio being powered with 5.07V?
Replies: 38
Views: 1446

Re: Low voltage warning even though gpio being powered with 5.07V?

All the size references in this thread so far where in AWG and OP is from the USA. Where I live and shop wire is only available in AWG sizes which is why my spreadsheet uses AWG. If anyone wants to modify the spreadsheet for mm^2 please feel free to do so and then maybe someday (unlikely before I di...
by Paul Hutch
Wed Sep 18, 2019 2:33 pm
Forum: General discussion
Topic: Low voltage warning even though gpio being powered with 5.07V?
Replies: 38
Views: 1446

Re: Low voltage warning even though gpio being powered with 5.07V?

Good idea measuring directly from the GPIO pins... 4.65V! I understand voltage drop, but never would have thought such a short length of wire could have made a difference this bad. Well I know better than to crank up the power supply. (fried a 3B doing that) What wire thickness is necessary? Here's...
by Paul Hutch
Thu Sep 12, 2019 8:51 pm
Forum: General discussion
Topic: serial connection with RFID equipment
Replies: 1
Views: 55

Re: serial connection with RFID equipment

I don't know if this will work but I'd try using /dev/ttyACM0 for the port name.
by Paul Hutch
Sat Sep 07, 2019 3:46 pm
Forum: General discussion
Topic: How to measure RPM using a Hall Effect Sensor
Replies: 11
Views: 444

Re: How to measure RPM using a Hall Effect Sensor

What is the frequency of the pulses in your application?

This is the type of application where, depending on the frequency, a microcontroller (possibly an Arduino) may be a much simpler, lower cost, lower power and more reliable solution.
by Paul Hutch
Sat Sep 07, 2019 3:01 pm
Forum: Python
Topic: Data input from an A/V cable
Replies: 11
Views: 670

Re: Data input from an A/V cable

This should have been the first reply in this thread.

What type of A/V cable?

What type of A/V data is used with the cable?
by Paul Hutch
Fri Sep 06, 2019 10:38 am
Forum: General discussion
Topic: crosscompile Qt5 on raspberry 4
Replies: 2
Views: 246

Re: crosscompile Qt5 on raspberry 4

Based on a recent post in the Python sub-forum, I believe QT5 (and PyQT5) is already an APT installable package for Buster.
by Paul Hutch
Fri Sep 06, 2019 10:23 am
Forum: Python
Topic: PyQt5 on Raspbian: Background color of QWidgets is not displayed
Replies: 7
Views: 302

Re: PyQt5 on Raspbian: Background color of QWidgets is not displayed

OK we can now be pretty sure it's not dependancy problem. I did a Google search and find that for many years this has been a common problem for users with QT (many QT forum posts). This thread seems to point to the root of the issue: https://forum.qt.io/topic/93418/cant-change-color-of-progressbar/8...
by Paul Hutch
Wed Sep 04, 2019 2:19 pm
Forum: Python
Topic: PyQt5 on Raspbian: Background color of QWidgets is not displayed
Replies: 7
Views: 302

Re: PyQt5 on Raspbian: Background color of QWidgets is not displayed

I've compiled and installed PyQt5 on a Raspberry Pi 3B+ running Raspbian Buster like described here . It took a few hours, but it worked. That StackExchange post is 2 years old so is likely obsolete in some way (I consider 6 months to be the shelf life of those type of posts). I haven't used Buster...
by Paul Hutch
Wed Aug 28, 2019 1:55 pm
Forum: General discussion
Topic: School project involving freezer
Replies: 9
Views: 410

Re: School project involving freezer

An experiment of a poorly described hypothesis that has had many inconsistent results due to the huge number of confounding variables is about the worst possible choice for an educational experience for a student.
by Paul Hutch
Mon Aug 26, 2019 1:20 pm
Forum: General discussion
Topic: Why moving to 64bit?
Replies: 259
Views: 20021

Re: Why moving to 64bit?

Ok, when is the 64-bit Raspbian coming out then? Just in time for the Pi 5. :roll: You've been around here long enough to know that release dates are never announced in advance. That soon? I'd expect more around the time of the Pi6 or Pi7. From 20 days ago at the beginning of this thread: I expect ...
by Paul Hutch
Fri Aug 23, 2019 7:54 pm
Forum: General discussion
Topic: Wifi
Replies: 2
Views: 115

Re: Wifi

I think you need to manually edit the configuration file to connect to a network with a hidden SSID. The documentation in the link below has instructions for hidden SSID setup.
https://www.raspberrypi.org/documentati ... ess-cli.md
by Paul Hutch
Sun Aug 18, 2019 12:46 pm
Forum: General discussion
Topic: Are Speaker Magnets A Problem For Pi?
Replies: 18
Views: 1735

Re: Are Speaker Magnets A Problem For Pi?

Just as an addendum, it's perhaps worth noting that the magnetic devices on board the Pi were designed to be as efficient as possible, which means they don't spray magnetic fields around if at all possible. The corollary is that stray magnetic fields around them have little effect. Speakers should ...
by Paul Hutch
Fri Aug 16, 2019 11:20 pm
Forum: General discussion
Topic: Are Speaker Magnets A Problem For Pi?
Replies: 18
Views: 1735

Re: Are Speaker Magnets A Problem For Pi?

If you discover a problem, mount a sheet of steel between the speaker and the Pi. Magnetic fields are tricky to shield. A simple sheet will just cause the field to wrap around the sides. This is based on spending much money and engineering effort to try and shield CRT monitors from a large transfor...
by Paul Hutch
Thu Aug 15, 2019 9:04 pm
Forum: General discussion
Topic: Official Keyboard and mouse
Replies: 33
Views: 1265

Re: Official Keyboard and mouse

I liked that keyboard, but it was not cost-effective. Mine lasted just beyond the warranty period. At the time, I think that was 3 years, so about $30/yr. MY Unicomp keyboard is (IIRC) over 10 years old and works just fine. Even if memory has failed, I had it before I got my first Pi in 2012. Not s...
by Paul Hutch
Wed Aug 14, 2019 11:55 pm
Forum: General discussion
Topic: Official Keyboard and mouse
Replies: 33
Views: 1265

Re: Official Keyboard and mouse

At home, both of us use Unicomp keyboards The finest keyboards I've ever bought, I have one in each work area of my home office connected to KVM's so Unicomp's drive 4 PC's and 3 Pi's. https://www.pckeyboard.com/ Why purchase an imitator when you can buy the original “Model M”. We have produced the...
by Paul Hutch
Wed Aug 07, 2019 1:23 pm
Forum: General discussion
Topic: Why moving to 64bit?
Replies: 259
Views: 20021

Re: Why moving to 64bit?

I had a 64b Alpha workstation in 1998-1999, after leaving university with its fleet of 64b Irix desktops. So yes, at least 20 years. Around 1996 we installed our first non-Novell server at work and it was a DEC Alpha based system. We ran NT 4.0 and were looking forward to the soon to be released 64...
by Paul Hutch
Tue Aug 06, 2019 12:18 pm
Forum: Python
Topic: Get pi CPU temp and load
Replies: 12
Views: 1633

Re: Get pi CPU temp and load

I've had good luck using the psutil library for getting CPU load.
https://pypi.org/project/psutil/
by Paul Hutch
Mon Aug 05, 2019 11:45 pm
Forum: General discussion
Topic: Pi Warranty?
Replies: 17
Views: 13071

Re: Pi Warranty?

Are you an employee, or somehow associated with Adafruit? Nope just someone who has seen many people on the Adafruit forum get warranty replacements for opened but defective products. The only posts I've seen where the warranty was refused were people who damaged the product themselves or waited to...
by Paul Hutch
Sat Aug 03, 2019 11:45 am
Forum: General discussion
Topic: Pi Warranty?
Replies: 17
Views: 13071

Re: Pi Warranty?

My personal experience with them was basically that "once you powered on the product, it has been used and returns are not accepted". Basically its all your fault - and if you don't agree its your fault, they ban you from their forum. Please provide a link to the Adafruit support forum posts where ...
by Paul Hutch
Tue Jul 30, 2019 7:11 pm
Forum: General discussion
Topic: High Endurance SD card
Replies: 47
Views: 18047

Re: High Endurance SD card

<snip> I am careful to buy only cards that are "sold and shipped by Amazon", as they seem to have a reliable supplier and they always send cards in their original factory packaging (definitely not frustration free but worth the trouble) <snip> My employer just started working with Amazon this year ...
by Paul Hutch
Mon Jul 29, 2019 2:26 pm
Forum: General discussion
Topic: Raspberry UPS
Replies: 8
Views: 347

Re: Raspberry UPS

Thanks for the link.

I'd even used their search using a copy paste of the name in the post, Pi Juice, and this is what it showed.
https://uk.pi-supply.com/search?type=product&q=Pi+Juice

Go to advanced search