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by Joel_Mckay
Sun May 12, 2019 2:19 am
Forum: Advanced users
Topic: i am working on surveillance robot using Rpi 3 b+ need to good algorithm for self navigation
Replies: 5
Views: 270

Re: i am working on surveillance robot using Rpi 3 b+ need to good algorithm for self navigation

Have a look at ROS or MRPT.

You will need to be more specific about the platform, as guidance and navigation are separate classes of problems.

Cheers.
J
by Joel_Mckay
Mon May 06, 2019 6:33 am
Forum: Advanced users
Topic: Seeking the illusive zero write
Replies: 14
Views: 675

Re: Seeking the illusive zero write

If you use an overlayfs then its only the upper of the merge mount that is readwrite so the only files are ones written to or writing are in ram and fetched from lower by the CoW (copy on write) of the overlayfs. The overlayfs method also allows one to track down which programs tend to slowly flood...
by Joel_Mckay
Fri May 03, 2019 6:43 am
Forum: Automation, sensing and robotics
Topic: Make a real robot
Replies: 17
Views: 655

Re: Make a real robot

Is ROS necessary for making the robot. Not always, but it will train you how to re-use a standard popular platform, and a minimal remote sensor/driver API. Both these concepts are important for understanding more complex platforms... yet you can start with just the turtle-bot sim demos. And i think...
by Joel_Mckay
Thu May 02, 2019 5:33 pm
Forum: Advanced users
Topic: MQ Gas sensor wire connection
Replies: 3
Views: 152

Re: MQ Gas sensor wire connection

The MCP3008 may require Vref to be less than or equal to Vcc (3.3v)... I'd use a Voltage divider on the sensor output to scale into a safe input range under 2.7v until this property is known.
https://en.wikipedia.org/wiki/Voltage_divider

;-)
by Joel_Mckay
Thu May 02, 2019 5:09 pm
Forum: Automation, sensing and robotics
Topic: Make a real robot
Replies: 17
Views: 655

Re: Make a real robot

In general, one must make several choices when designing a platform, and define the task you are trying to solve. Like any software specification, having a clearly defined finish line will constrain the complexity of your project. ROS ( https://wiki.ros.org/melodic ) is the current standard of sever...
by Joel_Mckay
Wed May 01, 2019 6:49 am
Forum: Troubleshooting
Topic: Pi 3B+ won't load Google-owned websites
Replies: 8
Views: 220

Re: Pi 3B+ won't load Google-owned websites

All of that will fail 100%. There's no NTP installed in Raspbian by default. Time sync is done with systemd-timedatectl. Even with ntp added after there's no ntpdate any longer (replaced with ntpd -q -g). And yes, 2 of the above lines will likely not work (20% fail to be exact)... depending on the ...
by Joel_Mckay
Wed May 01, 2019 6:27 am
Forum: Troubleshooting
Topic: Pi 3B+ won't load Google-owned websites
Replies: 8
Views: 220

Re: Pi 3B+ won't load Google-owned websites

If your device has a max time adjust forwards limit in NTP, and was left off too long... than SSL issues can occur. Try running: date sudo service ntp stop sudo ntpdate -s us.pool.ntp.org sudo ntpd -gq sudo service ntp start sudo ntpdate -u time.nist.gov date Then reboot the machine to retry your SS...
by Joel_Mckay
Wed May 01, 2019 6:11 am
Forum: Automation, sensing and robotics
Topic: how to write flash memory of mpu6050 for using dmp on board using python
Replies: 1
Views: 125

Re: how to write flash memory of mpu6050 for using dmp on board using python

InvenSense gyros tend to drift pretty badly/fast, and setting a low-pass down-sampling filter only gets you so far. A slower magnetometer is important as it usually offers the only true consistent directional reference using magnetic declination (once calibrated). Unfortunately, these "9-axis" units...
by Joel_Mckay
Tue Apr 30, 2019 11:51 am
Forum: Automation, sensing and robotics
Topic: What is the best way to add IR transmitter/receiver to raspberry pi 3 B+?
Replies: 6
Views: 314

Re: What is the best way to add IR transmitter/receiver to raspberry pi 3 B+?

They mention a 38KHz amplifier+de-modulator that runs at 3.3v just fine: https://www.adafruit.com/product/157 Keep in mind there are many different remotes, IR wavelengths, and any one of 34/38/40/56 kHz modulations. There were a few receivers that could auto-select several frequencies, but I can't ...
by Joel_Mckay
Tue Apr 30, 2019 7:38 am
Forum: Automation, sensing and robotics
Topic: What is the best way to add IR transmitter/receiver to raspberry pi 3 B+?
Replies: 6
Views: 314

Re: What is the best way to add IR transmitter/receiver to raspberry pi 3 B+?

sudo apt-get install lirc Then search for a tutorial about setting up the interface: http://alexba.in/blog/2013/01/06/setting-up-lirc-on-the-raspberrypi/ https://learn.adafruit.com/using-an-ir-remote-with-a-raspberry-pi-media-center/lirc This program has been around for a long time. https://gist.git...
by Joel_Mckay
Mon Apr 29, 2019 7:24 am
Forum: Automation, sensing and robotics
Topic: Lightning Sensor and external camera shutter release
Replies: 6
Views: 303

Re: Lightning Sensor and external camera shutter release

This camera likely supports tethering: http://gphoto.org/proj/libgphoto2/support.php People use several tricks to trigger the shutter in a lightning storm, and as they must be fast it usually limits the complexity of the circuit. In general, with a high-end capture rig ( https://www.krontech.ca/ ) y...
by Joel_Mckay
Sat Apr 27, 2019 11:20 pm
Forum: Automation, sensing and robotics
Topic: Random spikes with AM2302 Temperature & Humidity sensor
Replies: 3
Views: 134

Re: Random spikes with AM2302 Temperature & Humidity sensor

The reason many people use the bme280 is that it is reliable, accurate, and repeatable. Swapping sensors can be a pain, but sometimes using a different chip just works out being easier, and wastes less of your time in the long term. https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=239157 Actu...
by Joel_Mckay
Sat Apr 27, 2019 11:09 pm
Forum: Troubleshooting
Topic: Reducing 3b+ ARM clock speed - I/O issues
Replies: 4
Views: 117

Re: Reducing 3b+ ARM clock speed - I/O issues

The reason many people use the bme280 is that it is reliable, accurate, and repeatable. Swapping sensors can be a pain, but sometimes using a different chip just works out being easier, and wastes less of your time in the long term. https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=239157 Actu...
by Joel_Mckay
Sat Apr 27, 2019 7:46 am
Forum: Troubleshooting
Topic: An Introduction to C & GUI Programming
Replies: 1
Views: 87

Re: An Introduction to C & GUI Programming

I usually prefer a native cross platform C++ lib like wxwidgets for GUI stuff: https://wxwidgets.org/ (it has its own set of constraints, but works on most platforms) If wxglade wasn't so unstable, the visual layout scaffold coding experience would be trivial: http://wxglade.sourceforge.net/ https:/...
by Joel_Mckay
Sat Apr 27, 2019 7:27 am
Forum: Troubleshooting
Topic: USB Speaker is detected by EVERYTHING, but this thing refuses to output audio.
Replies: 8
Views: 204

Re: USB Speaker is detected by EVERYTHING, but this thing refuses to output audio.

Raspbian has "Raspberry Pi Desktop" which is a fork of LXDE......... We use a minimal MATE package on the Raspbian Stretch Lite image (MATE image itself seemed out of date), as it was more consistent with traditional Ubuntu/Mint style community documentation and supported a configurable gpu composi...
by Joel_Mckay
Sat Apr 27, 2019 6:52 am
Forum: Troubleshooting
Topic: USB Speaker is detected by EVERYTHING, but this thing refuses to output audio.
Replies: 8
Views: 204

Re: USB Speaker is detected by EVERYTHING, but this thing refuses to output audio.

fruitoftheloom wrote: Why do you believe the OP is running Gnome Desktop .
It is a common issue people may have, and the "volume control applet" is usually more meaningful than "pactl list; aplay -l;" or fumbling in the "alsamixer" terminal interface with F6 menu.

I assumed they are using linux... ;-)
by Joel_Mckay
Sat Apr 27, 2019 6:32 am
Forum: Troubleshooting
Topic: USB Speaker is detected by EVERYTHING, but this thing refuses to output audio.
Replies: 8
Views: 204

Re: USB Speaker is detected by EVERYTHING, but this thing refuses to output audio.

If you have the gnome desktop : 0. exit all active media players 1. right-click Speaker icon in the upper right hand of screen to select "Sound Preferences" 2. click "hardware" tab to see if driver is active 3. click "output" tab and select alternate default output line 4. click "hardware" tab again...
by Joel_Mckay
Sat Apr 27, 2019 6:11 am
Forum: Troubleshooting
Topic: DHT22 Accuraty.
Replies: 2
Views: 101

Re: DHT22 Accuraty.

We use the BME280 (several years of uptime), and I dumped the DHT/SHT units we sampled in the e-waste recycling bucket after testing the repeatability over several months (cleaved the leads off to ensure they stayed gone). I suggest you do the same... as although there will be a few people who insis...
by Joel_Mckay
Fri Apr 26, 2019 9:57 am
Forum: Advanced users
Topic: LM386 Audio Amp Module Producing buzzing/cracking noise
Replies: 6
Views: 254

Re: LM386 Audio Amp Module Producing buzzing/cracking noise

Many low-end sound-cards use a rather noisy class-d amplifier for the audio output. The picture/site doesn't really give enough details about the amp or sound-card. However, if a pair of headphones in the sound-card sound fine, than there are several possibilities: 1. you are over-driving the input ...
by Joel_Mckay
Fri Apr 26, 2019 9:15 am
Forum: Automation, sensing and robotics
Topic: Raspberry Pi Robot failure protection
Replies: 3
Views: 209

Re: Raspberry Pi Robot failure protection

Several big red mushroom buttons that say "Emergency Stop" to cut the main power for a start. ;-) The rather macabre "Dead man's switch" predates the modern computer age: https://en.wikipedia.org/wiki/Dead_man%27s_switch This is usually implemented with several redundant pic/atmel mcus with their ow...
by Joel_Mckay
Fri Apr 26, 2019 8:48 am
Forum: Advanced users
Topic: Any OS installer for Raspberry Pi 3 Plus with full encryption included?
Replies: 1
Views: 147

Re: Any OS installer for Raspberry Pi 3 Plus with full encryption included?

Why is that so hard to find? It is not difficult, but may be counter-intuitive to new users given the signal-to-noise ratio in web search results. LMGTFY: https://www.kali.org/tutorials/secure-kali-pi-2018/ Since the OS files are signed within apt one can usually just encrypt the user /home on publ...
by Joel_Mckay
Thu Apr 25, 2019 5:34 pm
Forum: Automation, sensing and robotics
Topic: PLC and Raspberry PI 3 B
Replies: 8
Views: 466

Re: PLC and Raspberry PI 3 B

A very general and broad statement, and IMHO inaccurate. I invite you to specify an ISO Standard that a RPi would fail to meet, but a PLC would. ... Lecture over, apologies to all. Excuse my obsession with anyone who makes sleeping, generalist statements, especially in a forum for beginners and stu...
by Joel_Mckay
Tue Apr 23, 2019 9:54 am
Forum: Troubleshooting
Topic: Excessive consumption of 3G with the change of summer time.
Replies: 1
Views: 85

Re: Excessive consumption of 3G with the change of summer time.

In general, there are many processes that can update, report, and download data. From your description, it sounds like IT debt... where the employee disappeared.... note, over 90% of security problems are usually current/former staff who are familiar with the systems. If you exposed an OS to the pub...
by Joel_Mckay
Tue Apr 23, 2019 9:30 am
Forum: Automation, sensing and robotics
Topic: PLC and Raspberry PI 3 B
Replies: 8
Views: 466

Re: PLC and Raspberry PI 3 B

You probably should look into a proper industrial HMI for you vendor's PLC, and a commercial VPN-appliance/router designed for this kind of application. The Pi is not intended for industrial environments, and will not meet legal or safety certification requirements without design specific lab paperw...
by Joel_Mckay
Tue Apr 23, 2019 5:02 am
Forum: Advanced users
Topic: Solution: Dedicating one core to a real-time process
Replies: 8
Views: 1967

Re: Solution: Dedicating one core to a real-time process

I just need to ensure that the maximum latency is under a hundred microseconds. This may ultimately depend on how tolerant your device is to timing jitter, and whether your 10 variables are concurrently sampled. https://en.wikipedia.org/wiki/Segal%27s_law One could compile linuxRT to get 5kHz task ...

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