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by PiGraham
Sun Jul 22, 2018 3:07 pm
Forum: General discussion
Topic: Is it suitable? For a Computer Science course?
Replies: 28
Views: 794

Re: Is it suitable? For a Computer Science course?

My son will be attending a Computer science course at uni in Sepetmber...would this be a useful thing to get in order to get him started in Computer science? If you are simply asking if comp sci students can get something out of having a Raspberry Pi then yes, absolutely. Get one! If you are asking...
by PiGraham
Thu Jul 19, 2018 10:00 pm
Forum: Graphics, sound and multimedia
Topic: * SIMULTANEOUSLY RECORD 2 VIDEOS *
Replies: 6
Views: 180

Re: * SIMULTANEOUSLY RECORD 2 VIDEOS *

I was only offering the basic concept as a starting point / interpretation of what the OP was seeking to do.
I sounds from what you say that it might be viable, using different tools. Two independent H264 compressed video streams could be multiplexed into a single vide file?
by PiGraham
Thu Jul 19, 2018 9:30 am
Forum: Graphics, sound and multimedia
Topic: * SIMULTANEOUSLY RECORD 2 VIDEOS *
Replies: 6
Views: 180

Re: * SIMULTANEOUSLY RECORD 2 VIDEOS *

Here's a suggestion for mux of two video streams Here is a simple (working) setup using gst-launch (install the gstreamer-tools package on Ubuntu/Debian): gst-launch v4l2src device=/dev/video1 ! videoscale ! ffmpegcolorspace ! video/x-raw-yuv, width=640, height=480 ! videobox border-alpha=0 left=-64...
by PiGraham
Thu Jul 19, 2018 8:58 am
Forum: Graphics, sound and multimedia
Topic: * SIMULTANEOUSLY RECORD 2 VIDEOS *
Replies: 6
Views: 180

Re: * SIMULTANEOUSLY RECORD 2 VIDEOS *

You may be able to multiplex two video streams into one file. That is typically how video and audio are combined in a file. Blocks of one data stream are interleaved or "multiplexed" with blocks of data for the other stream. You might be able to create a graph for gstreamer that does it. You could u...
by PiGraham
Thu Jul 19, 2018 8:39 am
Forum: Troubleshooting
Topic: 'Extending' USB - not working
Replies: 7
Views: 213

Re: 'Extending' USB - not working

You must run D+/- as twisted pair. Use actual USB cable. If you don't you alter the impedance and signal properties and that could easily make it not work as a USB connection. Routing USB through pin headers is not recommended for the sme reason but you might get away with it. USB connectors are des...
by PiGraham
Thu Jul 19, 2018 7:59 am
Forum: General programming discussion
Topic: What Does Hiding the Details of I/O in Library Calls Teach?
Replies: 63
Views: 1538

Re: What Does Hiding the Details of I/O in Library Calls Teach?

rpdom wrote:
Thu Jul 19, 2018 7:05 am
bensimmo wrote:
Thu Jul 19, 2018 6:32 am
That's when you get Orangutans.
In the library?
In the APE API?
by PiGraham
Wed Jul 18, 2018 5:38 pm
Forum: General programming discussion
Topic: What Does Hiding the Details of I/O in Library Calls Teach?
Replies: 63
Views: 1538

Re: What Does Hiding the Details of I/O in Library Calls Teach?

The whole idea of programming languages and symbolic instructions is obviously holding everyone back. Kids should be learning about computers by setting register load values on banks of switches. To be fair I can see benefits in kids learning about discrete logic circuits, how an adder can be made f...
by PiGraham
Wed Jul 18, 2018 5:29 pm
Forum: General programming discussion
Topic: What Does Hiding the Details of I/O in Library Calls Teach?
Replies: 63
Views: 1538

Re: What Does Hiding the Details of I/O in Library Calls Teach?

Of course the second one chooses Python to tackle a problem one has given up all hope of small size and performance. You can say that again. I rewrote a python program (it reads a BMP180 using the /sys interface and writes SQLite3 every three minutes) in C++ and the working set of the program goes ...
by PiGraham
Tue Jul 17, 2018 9:13 am
Forum: Automation, sensing and robotics
Topic: Is it possible to read the value of a UK dimmer switch with Raspberry Pi?
Replies: 21
Views: 514

Re: Is it possible to read the value of a UK dimmer switch with Raspberry Pi?

I now know after some research that the UK has some strange habits/tastes when it comes to light switches - we use a different circuit design (no earth), different sized fixings, and prefer different dimmer designs from everyone else! I've seen threads with people asking for Z-Wave dimmer switches ...
by PiGraham
Tue Jul 17, 2018 8:15 am
Forum: Automation, sensing and robotics
Topic: Is it possible to read the value of a UK dimmer switch with Raspberry Pi?
Replies: 21
Views: 514

Re: Is it possible to read the value of a UK dimmer switch with Raspberry Pi?

Thanks for the great answers folks.. it looks like I'm in over my head trying to get this to work the way I want! Imho Probably a lot less hassle to get a hot glue gun or a pot of epoxy resin and bodge a drilled face plate with a rotary encoder together for use or perhaps look at a 3d printed solut...
by PiGraham
Tue Jul 17, 2018 6:54 am
Forum: General discussion
Topic: Controlling 100 LEDs?
Replies: 12
Views: 380

Re: Controlling 100 LEDs?

Basically I want to be able to control about 16 or more electromagnets. To be able to turn them off and on from my PC. Each one is fairly small (dice sized) and doesn't require much current, although I will use an external power supply. Each electromagnet will keep a plate elevated or lowered depen...
by PiGraham
Mon Jul 16, 2018 10:28 pm
Forum: General discussion
Topic: Controlling 100 LEDs?
Replies: 12
Views: 380

Re: Controlling 100 LEDs?

The first thing to think about is to be clear about the objective. Work out if you need 100 discrete LEDs on a single Pi or or a string of 100 neopixels or a distributed system that is maybe networked together or a matrix LED panel. There are may possibilities and the best option may not be a HAT.
by PiGraham
Mon Jul 16, 2018 7:55 pm
Forum: General discussion
Topic: IVPort Dual camera multiplexer
Replies: 18
Views: 2602

Re: IVPort Dual camera multiplexer

Dear all, I need camera multiplexing IV Board to switch between my cameras. how long it takes to switch the camera? Suppose processing of images are performed in less than 5ms and there is no need to save images on disk, is it possible to capture image frames at 90 fps? Best Regars Bear in mind tha...
by PiGraham
Mon Jul 16, 2018 7:45 pm
Forum: Automation, sensing and robotics
Topic: Controlling homemade solenoids using Rpi Z W
Replies: 53
Views: 1143

Re: Controlling homemade solenoids using Rpi Z W

According to https://toshiba.semicon-storage.com/ap-en/product/linear/transistor-array/detail.ULN2003APG.html the datasheet for that particular part number ... Fixed that for you. It's noteworthy that Toshiba is EOLing that part, and recommending TBD62003. That uses a FET instead of a darlington, s...
by PiGraham
Mon Jul 16, 2018 7:32 pm
Forum: General discussion
Topic: Controlling 100 LEDs?
Replies: 12
Views: 380

Re: Controlling 100 LEDs?

Good advice, Just out of curiosity what's the max number of pins I can extend to even with additional products? There isn't really an answer to that. It depends how fast you need to upfdate states and how far signals have to travel. In general the further you need to go the slower and the more disc...
by PiGraham
Mon Jul 16, 2018 1:41 pm
Forum: Automation, sensing and robotics
Topic: Controlling homemade solenoids using Rpi Z W
Replies: 53
Views: 1143

Re: Controlling homemade solenoids using Rpi Z W

Soo we're probably stuck again. We got the ULN2003APG and followed this diagram https://imgur.com/a/cXkL5Wq on youtube except we didn't use the headers. Unfortunately the switch works on LEDS but not on our solenoid(We tested solenoids again because it was hard to find 12v batteries for the relays)...
by PiGraham
Mon Jul 16, 2018 1:33 pm
Forum: Automation, sensing and robotics
Topic: Controlling homemade solenoids using Rpi Z W
Replies: 53
Views: 1143

Re: Controlling homemade solenoids using Rpi Z W

Do you have any resistors in sries? The diagram shows LEDs with current limiting resistors, as needed for LEDs, but you don't want to add resistance to the solenoid circuit. What voltage do you measure at the ULN pin when the switch is on? What voltage do you measure at the battery +ve terminal when...
by PiGraham
Mon Jul 16, 2018 10:59 am
Forum: Beginners
Topic: camera preview on 3.5" hdmi lcd
Replies: 1
Views: 41

Re: camera preview on 3.5" hdmi lcd

Yes, of course. The camera preview naturally goes to the system default display which will be the HDMI display if there is one. You can get the raspistill / raspivid preview to display on other small TFT screens that connect by SPI bus if you run fbtft to provide a frame buffer and fbcp to automatic...
by PiGraham
Sun Jul 15, 2018 3:25 pm
Forum: Add-ons
Topic: Relay' connected to Rpi Zero W - causes it to freeze
Replies: 29
Views: 724

Re: Relay' connected to Rpi Zero W - causes it to freeze

1. I use common relays that operate at 5VDC, and triggered by gpio 3.3V. I do not think that labeling it as "Arduino" or "Raspberry Pi" does not make any technical difference. The technical difference has been explained several times but I'll to make it plain. Arduino gpio operates at 5V (Note ther...
by PiGraham
Sat Jul 14, 2018 8:06 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: ADC for analog video (possible?)
Replies: 26
Views: 734

Re: ADC for analog video (possible?)

Z80 Refugee wrote:
Fri Jul 13, 2018 9:41 pm
6by9 wrote:
Fri Jul 13, 2018 11:00 am
The Pi has hardware acceleration for H264 or MJPEG video encoding.
I think you mean video decoding.
It does both. If you use raspivid to record a video it uses H264 hardware encoder to compress it.
by PiGraham
Sat Jul 14, 2018 8:03 am
Forum: Automation, sensing and robotics
Topic: Controlling homemade solenoids using Rpi Z W
Replies: 53
Views: 1143

Re: Controlling homemade solenoids using Rpi Z W

It's very unlikely that we can find a neodymium magnet to use as a core here so we'll probably stick with the lollipop core and just compensate by using a bigger voltage battery to power the solenoids. Just a quick question about the transistors since we've decided to use them. Given that the PI ca...
by PiGraham
Fri Jul 13, 2018 6:07 pm
Forum: Automation, sensing and robotics
Topic: Controlling homemade solenoids using Rpi Z W
Replies: 53
Views: 1143

Re: Controlling homemade solenoids using Rpi Z W

How about using miniature neodymium magnets as the cores? Now you've confused even me! according to earlier posts, the coil (300 turns round a non-ferrous (?) lollipop stick) pulls a pin (probably iron) down So using a magnet for the core would just hold the pin permanently down. I'd use a steel sc...
by PiGraham
Fri Jul 13, 2018 6:03 pm
Forum: Automation, sensing and robotics
Topic: Controlling homemade solenoids using Rpi Z W
Replies: 53
Views: 1143

Re: Controlling homemade solenoids using Rpi Z W

How about using miniature neodymium magnets as the cores? Now you've confused even me! according to earlier posts, the coil (300 turns round a non-ferrous (?) lollipop stick) pulls a pin (probably iron) down So using a magnet for the core would just hold the pin permanently down. I'd use a steel sc...
by PiGraham
Fri Jul 13, 2018 4:29 pm
Forum: Automation, sensing and robotics
Topic: Controlling homemade solenoids using Rpi Z W
Replies: 53
Views: 1143

Re: Controlling homemade solenoids using Rpi Z W

0.5 seconds to go up and 0.5 seconds to go down would be ideal. The biggest goal we're trying to achieve for this is to make it as compact as possible. Have you made some really tiny solenoids? How big are they? Right now they're half an inch long and only have 300 turns so they're pretty thin as w...

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