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by jbeale
Sun Mar 22, 2020 2:55 am
Forum: Advanced users
Topic: PPS input signal: can there be more than one?
Replies: 4
Views: 372

Re: PPS input signal: can there be more than one?

As I show in a post above, the output of sudo ppstest /dev/pps0 /dev/pps1 contains data on alternating lines from the two PPS inputs. I don't have the exact syntax to hand, but it just took a few 'grep' commands to separate out the two data elements, and then generate a CSV file that I could import ...
by jbeale
Mon Mar 02, 2020 4:59 pm
Forum: General discussion
Topic: Pi Zero to precisely control peltier temp?
Replies: 13
Views: 563

Re: Pi Zero to precisely control peltier temp?

Measuring temperature accurately is always a challenge, but if you just need good resolution, a simple LM35 temperature sensor can resolve well below 0.1 C. This part is rated for 0.5 C accuracy and works from -55 to +150 C. http://www.ti.com/product/LM35 I use a LM35 and an 18-bit ADC (Microchip MC...
by jbeale
Wed Feb 26, 2020 1:40 am
Forum: General discussion
Topic: Pi4 1GB Availability? US Distributor Shows It As Discontinued
Replies: 27
Views: 1626

Re: Pi4 1GB Availability? US Distributor Shows It As Discontinued

If the Pi4 1GB was permanently discontinued that would mean no $35 option for the current model board, and that price point has always been pretty central to the Raspberry Pi brand. I'm just a regular user and in no position to know but it would be my GUESS it's a temporary situation.
by jbeale
Mon Feb 10, 2020 7:54 pm
Forum: Troubleshooting
Topic: Pi crashes every 24-48 hours. Logs?
Replies: 14
Views: 465

Re: Pi crashes every 24-48 hours. Logs?

One possibility to check on power issues with any USB device is to connect it through a separately powered USB hub, making sure the hub has its own solid power supply. Obviously this is inconvenient and more bulky but for testing purposes it could rule out power issues as the cause.
by jbeale
Mon Feb 10, 2020 6:33 pm
Forum: Off topic discussion
Topic: Private contact with other forum users
Replies: 13
Views: 1178

Re: Private contact with other forum users

None of the schools I know of serving pre-teen students provide for private messaging to anyone outside the school on their networks. That is a demographic the RPi organization is clearly trying to serve, and I would expect them to do the same things, for the same reasons. A web search for "disposab...
by jbeale
Sun Feb 09, 2020 6:49 pm
Forum: Camera board
Topic: Accessing data from the individual photosensors in a RPI cameramodule
Replies: 2
Views: 219

Re: Accessing data from the individual photosensors in a RPI cameramodule

I assume you would want the "RAW" output format. There has been some discussion of the RAW mode, see for example on this thread: https://www.raspberrypi.org/forums/viewtopic.php?f=43&t=44918&start=225#p1400418 This paper might be relevant: "Suitability of the Raspberry Pi camera for cosmic ray detec...
by jbeale
Fri Feb 07, 2020 5:11 pm
Forum: Troubleshooting
Topic: Pi crashes every 24-48 hours. Logs?
Replies: 14
Views: 465

Re: Pi crashes every 24-48 hours. Logs?

One thing that can cause crashes is a momentary power glitch. Wifi uses very short high-current bursts during transmission; moreso I believe than the wired ethernet interface. If the Pi's power supply or the power supply cable is marginal, I think it is possible the momentary peak power drain of a w...
by jbeale
Thu Jan 30, 2020 10:45 pm
Forum: General discussion
Topic: Distance Sensors
Replies: 8
Views: 831

Re: Distance Sensors

"The consistency from bottom to top goes from solids, to water, to oil, to cream, to foam, to air." That is an interesting (aka "difficult") measurement problem, because from this description the "surface" of the stuff in the container is not well defined. You would get a nice clean echo from sound ...
by jbeale
Wed Jan 29, 2020 10:07 pm
Forum: General discussion
Topic: downloading raspbian: too slow
Replies: 58
Views: 13128

Re: downloading raspbian: too slow

I think the moral of the story, if I may say so, is that Internet download speed is a very complex thing, because of the complex nature of the modern internet. The speed of your download is set by the speed of the slowest link between the remote server and your client, and if the server is half the ...
by jbeale
Thu Jan 23, 2020 6:04 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Waveshare High-Res ADC board (SPI) code
Replies: 8
Views: 2145

Re: Waveshare High-Res ADC board (SPI) code

As far as I could tell, this ADC board does not work properly at its two highest ADC rates on the R-Pi, even using C code. Using Python which is generally slower, I expect it would be worse. 600 samples in 1/50 second means 30000 samples per second. The specs may say the board can do this, but my ex...
by jbeale
Mon Jan 20, 2020 5:47 pm
Forum: Off topic discussion
Topic: For mahjongg Moderator , On his remark on my post
Replies: 22
Views: 1841

Re: For mahjongg Moderator , On his remark on my post

FWIW I don't know about RPF specifically but as a practical matter, it is my experience that email addresses that were required to sign up for an online forum are not guaranteed to be anyone's main email address, or to be frequently checked by anyone. Or possibly even still valid if some time has pa...
by jbeale
Fri Jan 17, 2020 1:47 am
Forum: General discussion
Topic: does the RPI 4b have backfeed protection?
Replies: 3
Views: 364

Re: does the RPI 4b have backfeed protection?

The Pi does have a chip that measures total current going out through the USB ports, and shuts the port supply off if the total exceeds 1.2 amps. So if the Pi gets a backfeed that number will go down, and if the Pi is actually powered from the USB port the number would go negative. What happens in t...
by jbeale
Wed Jan 15, 2020 10:22 pm
Forum: Camera board
Topic: Longest possible Cable for Pi Camera and why?
Replies: 8
Views: 558

Re: Longest possible Cable for Pi Camera and why?

The Raspberry Pi supports only one MIPI CSI type camera (the kind using a flat ribbon cable). I saw one person assume the LCD display connector could also be used a camera connector since they both have 15 pins, but of course that not true. I am not sure, but maybe you are thinking about the 4-to-1 ...
by jbeale
Fri Jan 10, 2020 5:53 pm
Forum: Automation, sensing and robotics
Topic: Pi somehow control wifi light dimmer ?
Replies: 11
Views: 929

Re: Pi somehow control wifi light dimmer ?

Interesting to learn about Tasmota, I see it does support wifi dimmers like "PS-16-DZ" containing ESP8285 and a Nuvoton N76E003, so that's another choice... but once I reflash firmware, I'm completely owning responsibility for how something that in my case could draw 120V * 15A = 1800W is controlled...
by jbeale
Fri Jan 10, 2020 3:34 pm
Forum: Automation, sensing and robotics
Topic: Pi somehow control wifi light dimmer ?
Replies: 11
Views: 929

Re: Pi somehow control wifi light dimmer ?

Thanks for the reply. I saw wifi-enabled switches and dimmers starting around $25 which seemed like a good value, and I know I have a wifi signal into the garage, which is where I want the light (just one, for now). It seems like the hardware should work, but the software isn't designed to be used s...
by jbeale
Fri Jan 10, 2020 4:32 am
Forum: Automation, sensing and robotics
Topic: Pi somehow control wifi light dimmer ?
Replies: 11
Views: 929

Pi somehow control wifi light dimmer ?

I see there are now many home automation parts like light dimmer switches that have wifi built in, which are advertised to be compatible with cloud services like Apple Home or Google Alexa. (I think anyway, I don't use either of those.) I guess that's good for the average consumer, but I would like ...
by jbeale
Thu Jan 09, 2020 10:26 pm
Forum: General discussion
Topic: PCIe over cable standard. I didn't know that was a thing.
Replies: 22
Views: 1255

Re: PCIe over cable standard. I didn't know that was a thing.

USB3 has a reasonable amount of bandwidth and the electrical interface is designed to run over a cable. I'm not up to speed on the details, but I had the impression PCIe signals are less suitable to run over a cable, being intended for cards mounted directly on a motherboard (?)
by jbeale
Mon Jan 06, 2020 5:36 pm
Forum: Automation, sensing and robotics
Topic: Building a deep learning model for Semantic segmentation on Raspberry Pi
Replies: 14
Views: 870

Re: Building a deep learning model for Semantic segmentation on Raspberry Pi

Reasonably accurate object detection and localization (on a 2D image plane) is possible on the RPi4 if you are willing to wait several seconds per frame. Pixel-wise semantic segmentation would likely be significantly slower. It sounds to me like you want to use the lowest-powered computer to do stat...
by jbeale
Mon Jan 06, 2020 7:23 am
Forum: General discussion
Topic: Outdoor Security Sensors
Replies: 11
Views: 561

Re: Outdoor Security Sensors

Does anyone have thoughts on achieving long cable runs with 3V3? I think you'll find that any significant length of wire connected directly to a GPIO pin is an invitation to trouble via capacitive and inductive pickup everywhere from DC (electrostatic) up to radio interference. There is a particula...
by jbeale
Sun Jan 05, 2020 9:14 pm
Forum: General discussion
Topic: Adding a second USB camera
Replies: 9
Views: 820

Re: Adding a second USB camera

Even the Pi Zero allows to use 3 USB cameras in parallel: https://www.raspberrypi.org/forums/viewtopic.php?f=63&t=161121 Impressive experiment! You might also mention if that is video, at what resolution and framerate. My Pi4 experiment was two cameras at 640x480 and 30fps. I would be surprised if ...
by jbeale
Sun Jan 05, 2020 6:17 am
Forum: General discussion
Topic: Adding a second USB camera
Replies: 9
Views: 820

Re: Adding a second USB camera

In general, when you have two USB cameras plugged in, you should see /dev/video0 and /dev/video1 show up, along with some kind of messages about each camera somewhere in the output of the 'dmesg' command. If each camera is compatible with the Pi (eg. it works OK by itself) but they don't work togeth...
by jbeale
Sat Jan 04, 2020 7:00 pm
Forum: Troubleshooting
Topic: [SOLVED] Raspberry Pi 4 not receiving 1000 Mbps
Replies: 16
Views: 1159

Re: Raspberry Pi 4 not receiving 1000 Mbps

For what it's worth, using iperf between Intel J3455 Linux Mint box and Pi4: with Pi4 as server I see 938 Mb/s and as client, 895 Mb/sec Between two different Pi4 (one running raspbian, one running ubuntu) I get 930 to 940 Mb/s using for example, iperf -s on one side and iperf -i 10 -t 60 -c 192.168...
by jbeale
Sat Jan 04, 2020 6:08 pm
Forum: Advanced users
Topic: USB SSD Fails on Large File on RPi4
Replies: 18
Views: 1309

Re: USB SSD Fails on Large File on RPi4

occasionally pulling more than the 1.2A max supported by the Pis USB setup I feel it is worth underlining that part: there is no use or benefit to a larger power supply, if the problem is current limiting on the Pi's total USB current output (sum total current draw of all attached USB devices). One...
by jbeale
Sat Jan 04, 2020 5:25 pm
Forum: Advanced users
Topic: USB Camera issue with Pi 4B
Replies: 4
Views: 636

Re: USB Camera issue with Pi 4B

I don't know what to recommend. I tried searching for "Logitech B525 linux" and I have not seen any reports of that camera working with any Linux systems. There are reports that the Logitech C525 works though. Here is a list of some webcams that Linux does have drivers to support: http://www.ideason...
by jbeale
Sat Jan 04, 2020 4:43 am
Forum: General discussion
Topic: having issues with 4 relay and raspberry pi 4
Replies: 23
Views: 1051

Re: having issues with 4 relay and raspberry pi 4

Do you have any documentation for this 4-relay board you are using? Is it this "SainSmart 4-Channel 5V Relay Module", that says it needs 15 to 20 mA of current for each input? https://www.amazon.com/SainSmart-101-70-101-4-Channel-Relay-Module/dp/B0057OC5O8/ I don't know if it's the same board but I ...

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