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by Joel_Mckay
Thu Oct 25, 2018 10:35 am
Forum: General discussion
Topic: Powering both LED strip and Raspberry Pi with one Power Supply?
Replies: 3
Views: 2210

Re: Powering both LED strip and Raspberry Pi with one Power Supply?

Please read this to understand why your power supply is too small for an 18W LED strip at 5v: https://en.wikipedia.org/wiki/Watt (The additional load of the pi will likely demand a >5.5A 5v supply....) Sharing a power-switching load with a single logic supply is also a bad idea... Use two step-down ...
by Joel_Mckay
Thu Oct 25, 2018 10:21 am
Forum: General discussion
Topic: logging of light intensity
Replies: 5
Views: 623

Re: logging of light intensity

The TSL2561 i2c device is good for the visible spectrum, and has lots of sample projects around.

Cheers,
J
by Joel_Mckay
Thu Oct 25, 2018 10:14 am
Forum: General discussion
Topic: Raspberry or PLC for project
Replies: 1
Views: 294

Re: Raspberry or PLC for project

PLC are expensive because they are certified for operation in industrial settings (UL/CE & FCC/IEC stamps etc.) In general, commercial insurance companies will not cover custom hardware somebody bodged together, and the city inspector can shut you down for bending the bylaws. You could go for lab ce...
by Joel_Mckay
Thu Oct 25, 2018 6:41 am
Forum: Automation, sensing and robotics
Topic: Project: Sorting robot using camera
Replies: 13
Views: 3671

Re: Project: Sorting robot using camera

Template matching is usually used for looking at closely matching image tiles, and is not designed to account for different orientations. This is a classic problem, and a common assignment for an undergraduate level coarse. In general, the camera used for high-speed lines runs at lower resolutions (...
by Joel_Mckay
Thu Oct 25, 2018 1:57 am
Forum: Automation, sensing and robotics
Topic: Project: Sorting robot using camera
Replies: 13
Views: 3671

Re: Project: Sorting robot using camera

1. Pick up a book about OpenCV https://www.amazon.com/Learning-OpenCV-Computer-Vision-Library/dp/0596516134 2. Control your camera lighting to make the camera input consistent. 3. Control your camera glare with filters 4. cvPosit or solvePnp with dlib example http://dlib.net/ https://www.learnopencv...
by Joel_Mckay
Tue Oct 23, 2018 12:20 pm
Forum: General discussion
Topic: Oh damn, it's happened! Charging a lot of pis?
Replies: 10
Views: 1683

Re: Oh damn, it's happened! Charging a lot of pis?

they do a 40 node pi rack which is lots of quattro blades in a nice rack: http://my.bitscope.com/store/?p=list&a=list&i=cat+blade Those look awesome, but the onboard regulators look a bit small for four pi3b+, as we've measured about 1.8A peak loads with wifi running (although, the pi2 were nowhere...
by Joel_Mckay
Tue Oct 23, 2018 11:14 am
Forum: General discussion
Topic: Oh damn, it's happened! Charging a lot of pis?
Replies: 10
Views: 1683

Re: Oh damn, it's happened! Charging a lot of pis?

As rotwang has alluded, there are quite large power supplies available. However, you may want to look for an older pre-Rosewill unit that actually has more power available on the +5v rail. These can be a little tricky to setup if you have never worked with load minimums before, but we use them at ou...
by Joel_Mckay
Tue Oct 23, 2018 10:58 am
Forum: Advanced users
Topic: Recovering my software
Replies: 4
Views: 979

Re: Recovering my software

I have provisioned hundreds of sdcards over the years, and would recommend using a Mint/Ubuntu OS desktop with "gnome-disk" (from "sudo apt-get install gnome-disk-utility"). Get the disk backup process tested on another card to teach yourself how not to accidentally delete the usb-to-sdcard adapter ...
by Joel_Mckay
Tue Oct 23, 2018 3:29 am
Forum: Automation, sensing and robotics
Topic: Creating a Self driving Lawnmower
Replies: 6
Views: 3914

Re: Creating a Self driving Lawnmower

A practical api is fine: https://www.mrpt.org/ Or the hilariously huge ROS framework if computing power is available. ;-) Many warehouse robots simply use magnetic pickups from a signal-wire embedded in the ground, as it works as both a fence and location identifier. Proximity doppler-radar modules ...
by Joel_Mckay
Mon Oct 22, 2018 1:43 am
Forum: Graphics, sound and multimedia
Topic: Video on browser, chromium
Replies: 1
Views: 1549

Re: Video on browser, chromium

MP4 is not normally meant for streaming playback. Basically, you have to copy the media information to the beginning of the file: https://stackoverflow.com/questions/10328401/html5-how-to-stream-large-mp4-files#10330501 Also, to support random seek (or fast forward) you will need a special web serve...
by Joel_Mckay
Mon Oct 22, 2018 1:04 am
Forum: General discussion
Topic: Calibration of atmospheric pressure BME280
Replies: 2
Views: 1894

Re: Calibration of atmospheric pressure BME280

In general, the barometric pressure can only approximate altitude... correcting it by modeling temperature and humidity. Indoors is always different than outdoors, and even people breathing on the sensor will change humidity. However, it mainly is related to which model the authors chose to implemen...
by Joel_Mckay
Mon Oct 22, 2018 12:53 am
Forum: Automation, sensing and robotics
Topic: Using RPI link with PLC
Replies: 2
Views: 1278

Re: Using RPI link with PLC

I have done this commercially on Linux, and it is usually a deep dive into the vendor specifications with zero support.

Best of luck,
J
by Joel_Mckay
Sun Oct 21, 2018 11:34 am
Forum: General discussion
Topic: solid pwm for motor
Replies: 2
Views: 436

Re: solid pwm for motor

The atmega2560 has no problem running 10 hardware PWMs at a time. (I have used these to run several DRV8833 at a time)

If you are looking for a half/full h-bridge driver, than the pic18f4550 has a special pwm that handles this task (10bit precision if I recall).
;-)

Best of luck,
J
by Joel_Mckay
Sun Oct 21, 2018 11:23 am
Forum: General discussion
Topic: 'Data Science' relatable MSc project sought
Replies: 4
Views: 768

Re: 'Data Science' relatable MSc project sought

The first steps in real scientific inquiry is asking "why are you doing it", and "how it will benefit civilization". Take it from someone that spent years of their life reading reported nonsense-findings by the optimistic: http://www.academiaobscura.com/still-not-significant/ ;-) Julia is like R, oc...
by Joel_Mckay
Fri Oct 19, 2018 2:27 pm
Forum: Automation, sensing and robotics
Topic: Project with 3x linear encoders and 3x stepper motors simultaneously
Replies: 1
Views: 1081

Re: Project with 3x linear encoders and 3x stepper motors simultaneously

Most stepper motor driven machines are open-loop control, but LinuxCNC does support industrial servo based closed-loop style systems on larger machines. Personally, I use steppers on my small home mill, lathe, and 3d printer. We released a special RTLinux based linuxCNC distro with simple CAM tools ...
by Joel_Mckay
Thu Oct 18, 2018 8:43 am
Forum: Advanced users
Topic: Using my Pi with an AC mains connected preamp.
Replies: 12
Views: 1769

Re: Using my Pi with an AC mains connected preamp.

@hippy It does sound rather dodgy, but legal guidelines are usually made by people with zero engineering background. Rules like RoHS actually made equipment more unreliable, and even NASA had to spend a few million $ to figure out why. @Imperf3kt Even if the chassis enclosure is grounded to earth, I...
by Joel_Mckay
Thu Oct 18, 2018 6:49 am
Forum: Advanced users
Topic: Using my Pi with an AC mains connected preamp.
Replies: 12
Views: 1769

Re: Using my Pi with an AC mains connected preamp.

In general, you want to isolate your equipment if possible: https://en.wikipedia.org/wiki/Ground_loop_%28electricity%29 "Neutral is connected directly to the ground plane of the amplifier" sounds a bit like a widow maker.... ;-) Maybe two small Toroidal audio isolation-transformers could be a feasib...
by Joel_Mckay
Thu Oct 18, 2018 5:11 am
Forum: Automation, sensing and robotics
Topic: Automated device
Replies: 3
Views: 840

Re: Automated device

We talked to some people they suggested the Pi might crash if it is operating that many motors. Me and my group would appreciate any input, also what would be best way to connect that many motor to the pi. We use 8-axis stepper controllers with the pi all the time for our CNC club's machines: http:...
by Joel_Mckay
Thu Oct 18, 2018 4:23 am
Forum: Automation, sensing and robotics
Topic: Sound Sensor - Counting Trains
Replies: 2
Views: 802

Re: Sound Sensor - Counting Trains

Probably a usb sound-card/microphone or accelerometer would be more reliable. I'd look for loud low-frequency rumbling peaks with a simple DFT in: https://github.com/mborgerding/kissfft Or a python wrapper for the awesome GSL library which does just about everything ( like finding treasure ;-) ) htt...
by Joel_Mckay
Thu Oct 18, 2018 3:54 am
Forum: Troubleshooting
Topic: [SOLVED] Cannot Connect Via Ethernet - Router Problem?
Replies: 8
Views: 646

Re: Cannot Connect Via Ethertnet - Router Problem?

Usually if the Ethernet plug on the router doesn't show link activity, then you have a wiring issue. Simply try another cat5/6 cable after rebooting the router, and then rebooting the pi. There can be several reasons for reach-ability issues: * wrong type of cable other network cards can auto correc...
by Joel_Mckay
Wed Oct 17, 2018 11:25 pm
Forum: Troubleshooting
Topic: Under Voltage Detected despite usb power injection from PC PSU
Replies: 3
Views: 498

Re: Under Voltage Detected despite usb power injection from PC PSU

You will probably find that the ATX power supply needs a certain amount of load on the 5V rail and possibly other power rails as well before the supply voltage output is stable at the correct voltage. When I converted an ATX power supply into a bench top PSU I found I needed a 10 ohm 10 watt resist...
by Joel_Mckay
Tue Oct 16, 2018 8:33 pm
Forum: Automation, sensing and robotics
Topic: Quadcopter autopilot
Replies: 1
Views: 610

Re: Quadcopter autopilot

Please tell me any autopilot models for quadcopter with the possibility of upgrading to connect other sensors and with possibility of improving the whole system of autopilot (does not require full autonomy, but only the possibility of flying with / without remote control) There are many commercial ...
by Joel_Mckay
Tue Oct 16, 2018 1:58 am
Forum: Automation, sensing and robotics
Topic: 1945 Craftsman lathe CNC Conversion
Replies: 7
Views: 1974

Re: 1945 Craftsman lathe CNC Conversion

A lathe is normally only two axis. Unless you add a tool turret rather than multiple posts. ;-) A Pi could control the steppers reasonably without extra hardware like an Arduino. Not from our personal experiences, as an Arduino can do "Real-Time" control using a low-level timer interrupt, and runs ...
by Joel_Mckay
Mon Oct 15, 2018 9:28 pm
Forum: Automation, sensing and robotics
Topic: 1945 Craftsman lathe CNC Conversion
Replies: 7
Views: 1974

Re: 1945 Craftsman lathe CNC Conversion

My page about NEMA steppers: http://www.micrometer.xyz/cdn/node/68 RTLinux Debian Stretch distro focused on CNC (includes lathe specific CAM tools for linuxCNC) https://sourceforge.net/projects/micrometer-cnc-on-raspberry-pi (I plan to get an arbitrary threading encoder setup done next summer) The b...
by Joel_Mckay
Sun Oct 14, 2018 10:56 pm
Forum: Assistive technology and accessibility
Topic: Does this exist: HDMI Flashing Filter Device?
Replies: 3
Views: 8758

Re: Does this exist: HDMI Flashing Filter Device?

In VLC player, there is a setting that enables something call frame-averaging.

Not sure if the pi could handle the workload, but the filter can be adjusted to convert blinks into a fade-out.

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