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by MarkR
Thu Jun 27, 2019 8:45 am
Forum: General discussion
Topic: anti-Virus and anti-Malware software for the Pi?
Replies: 39
Views: 2584

Re: anti-Virus and anti-Malware software for the Pi?

Linux AV software is widely available and generally very useful when Linux is used on a server, because while most malware won't run under Linux, e.g. Windows or Mac malware can certainly be spread by e.g. a file or web server. Unfortunately the A+ Antivirus apps are all x86-only because they usuall...
by MarkR
Thu Jun 27, 2019 8:36 am
Forum: General discussion
Topic: 1 GB RAM Raspberry Pi 4 Optimization
Replies: 13
Views: 1628

Re: 1 GB RAM Raspberry Pi 4 Optimization

I sometimes use compressed RAM, e.g. "zram" to improve things on systems with low memory. I haven't tried it on the latest distribution, but previously there was a package called "zram-config" which can be installed and will just set reasonable default settings for compressed ram. Also remember that...
by MarkR
Wed Jun 12, 2019 9:49 am
Forum: Automation, sensing and robotics
Topic: irritating battery limits
Replies: 21
Views: 1193

Re: irritating battery limits

If you have a smart enough charge controller, it will be able to provide power while charging. Or you could use a separate boost converter to power the Pi from the cells all the time, there is no problem doing this while charging. Mobile phones obviously manage to do this. As far as connecting cells...
by MarkR
Wed Jun 12, 2019 9:45 am
Forum: Automation, sensing and robotics
Topic: How to measure distance with the raspberry pi camera
Replies: 4
Views: 354

Re: How to measure distance with the raspberry pi camera

It is possible to measure the distance to a target approximately using the camera, if you have a calibration sign attached to the target and use machine vision to identify it and measure the angular size. I have done this. It won't work for a unlabelled target whose size isn't known precisely ahead ...
by MarkR
Mon Jun 10, 2019 1:43 pm
Forum: Automation, sensing and robotics
Topic: How many ultrasonic hc-sr04 can I connect ?
Replies: 4
Views: 217

Re: How many ultrasonic hc-sr04 can I connect ?

There are a lot of different ways you can wire them up. The sensors don't necessarily need two GPIO lines each. You could wire the echo (Pi input / response) pins together, perhaps with diodes if required and/or pull up/down resistors, so that you only need one GPIO input pin for several sensors. Yo...
by MarkR
Fri Jun 07, 2019 10:26 pm
Forum: Automation, sensing and robotics
Topic: How about a tutorial for building just one independent drone?
Replies: 2
Views: 207

Re: How about a tutorial for building just one independent drone?

I recommend finding some local drone builders and building a non-raspberry-pi based drone, using off-the-shelf parts or one of the commonly available control boards. There are a lot of issues to deal with - weight, balance, batteries, electrics, motors, electronics, radio receivers, learning to pilo...
by MarkR
Fri May 24, 2019 1:59 pm
Forum: Automation, sensing and robotics
Topic: Auto Update Raspbian
Replies: 6
Views: 7246

Re: Auto Update Raspbian

Or if your distribution already knows how to do automatic updates (I think recent Raspbian does), then you can configure its auto updates If this file exists: /etc/apt/apt.conf.d/50unattended-upgrades Then edit it. It has some comments explaining. Also, running automatic updates in rc.local is quite...
by MarkR
Tue May 07, 2019 5:41 pm
Forum: Automation, sensing and robotics
Topic: Motors - What Type, How to use?
Replies: 7
Views: 560

Re: Motors - What Type, How to use?

"The black wire (negative) must be connect to the same negative rail as the Raspberry Pi." I said that, because you can run the motors from a separate power supply from the Pi, but they need to be referenced to the same "ground" level. Two batteries which are not connected in any way, are just "floa...
by MarkR
Tue May 07, 2019 5:34 pm
Forum: Automation, sensing and robotics
Topic: An easy to build PWM controlled DC motor driver
Replies: 6
Views: 613

Re: An easy to build PWM controlled DC motor driver

I'm not sure how it's supposed to be "easy to build" with a SMT IC which has a pitch of 0.65mm, that's pretty tricky soldering territory. Nor is it immediately obvious how this interfaces with the Pi. There are also approximately a zillion existing DRV8833 breakout boards available from the usual su...
by MarkR
Sun May 05, 2019 2:28 pm
Forum: Automation, sensing and robotics
Topic: Motors - What Type, How to use?
Replies: 7
Views: 560

Re: Motors - What Type, How to use?

Right, these are continuous servos. Continuous servos are great because they don't need a separate motor control board, the electronics is built-in. The red and black wires connect the power (positive and negative respectively). Do not connect this through the Pi gpio header, but instead connect it ...
by MarkR
Wed Apr 24, 2019 5:24 pm
Forum: Automation, sensing and robotics
Topic: Outdoor Pond Water Level Control / Valve
Replies: 9
Views: 623

Re: Outdoor Pond Water Level Control / Valve

Whatever you use, it needs to work reliably outside and get a bit wet. I wouldn't recommend sticking electrodes in the water, that will probably fail quite quickly (corrosion, bioslime etc). A float switch sounds fairly plausible (although why wouldn't you just use a toilet fill valve?). Ultrasonics...
by MarkR
Wed Apr 10, 2019 9:20 pm
Forum: Automation, sensing and robotics
Topic: Can L298N power up a Raspberry Pi?
Replies: 3
Views: 240

Re: Can L298N power up a Raspberry Pi?

Check the specs, most pcb-mounted regulators will run a Zero, but not a Pi 3 or something. Depends which Pi.
by MarkR
Tue Apr 02, 2019 6:04 pm
Forum: Automation, sensing and robotics
Topic: Servo control using PWM
Replies: 8
Views: 947

Re: Servo control using PWM

If you're using a web app, then probably your program / script won't keep running once the web request is finished. This is probably not what you want, if the servo motor is still trying to move to its position. Personally, I like the pigpio library / daemon, so I'd install that, and have your web a...
by MarkR
Tue Apr 02, 2019 8:48 am
Forum: Automation, sensing and robotics
Topic: Remote Tank level sensor queries
Replies: 11
Views: 614

Re: Remote Tank level sensor queries

I think you don't need the level shifter, Adafruit's page says it works with 3.3v. How far away is the remote water tank? Does it have line of sight? If it's simply a bit too far away for wifi, consider using one of the long range radios (Zigbee, Lora, some NRF thing) which will enable transmitting ...
by MarkR
Mon Mar 11, 2019 10:11 am
Forum: Automation, sensing and robotics
Topic: servo motor not working
Replies: 6
Views: 409

Re: servo motor not working

You would expect a LED connected to a servo output to glow very dimly, as such outputs will be driving with a 10% duty cycle at a maximum (5% typically in centre position)

The pulses are usually sent every 20ms, but at 1-2ms long.
by MarkR
Mon Feb 25, 2019 12:36 pm
Forum: Automation, sensing and robotics
Topic: Sensing the level/volume of a tank full with woodchips
Replies: 13
Views: 873

Re: Sensing the level/volume of a tank full with woodchips

It may be a major mechanical change, but, place the whole tank on a load-cell, and measure the weight? My guess (I haven't worked with woodchip systems myself) is that it will be a messy, dusty, possibly damp environment which will destroy many types of sensors easily. So while lots of things might ...
by MarkR
Mon Feb 25, 2019 12:00 pm
Forum: Automation, sensing and robotics
Topic: Sensing the level/volume of a tank full with woodchips
Replies: 13
Views: 873

Re: Sensing the level/volume of a tank full with woodchips

The laser time-of-flight sensors would be ok with woodchips, I imagine. They work well in the dark (not so well outside in sunshine). One problem might be dust and crud building up on the sensor. The time-of-flight sensors can cope with a piece of glass in front of the sensor, it would need cleaning...
by MarkR
Fri Feb 22, 2019 11:12 pm
Forum: Automation, sensing and robotics
Topic: Ultrasound sensor alternatives?
Replies: 11
Views: 1240

Re: Ultrasound sensor alternatives?

No, there is no obvious register map. The example software is open source, but it is intended for some uncommon microcontrollers. There is at least one port to Raspberry Pi (and also Arduino, and other microcontrollers) - these ports were all made by effectively reverse-engineering or adapting the d...
by MarkR
Fri Feb 22, 2019 10:50 am
Forum: Automation, sensing and robotics
Topic: Ultrasound sensor alternatives?
Replies: 11
Views: 1240

Re: Ultrasound sensor alternatives?

Those VL53 time-of-flight sensors are super good. They really are impressive, they give very accurate ranging with a narrow beam width in my tests. I heard they don't work too well outside during the day, but I've not tried that yet. It's an I2C interface and the address can be changed through I2C, ...
by MarkR
Tue Feb 19, 2019 10:36 am
Forum: Automation, sensing and robotics
Topic: Fuse between motor driver board and power source?
Replies: 12
Views: 742

Re: Fuse between motor driver board and power source?

I would say that it's probably strictly unnecessary, even if you would use a much more powerful battery. Suppose you switch to a 2S Lipo pack rated at something like 30A continuous (these are easily available and are commonly used on quadcopters, etc). The robot is never going to run: * Unattended -...
by MarkR
Tue Feb 12, 2019 11:59 am
Forum: Automation, sensing and robotics
Topic: Sending Video to a Database
Replies: 2
Views: 213

Re: Sending Video to a Database

I would not recommend storing videos in a database. You can - of course - use a database to store videos, using some type of "blob" column- and store metadata (date/time, device ID etc) in other columns. But maybe it's easier to just put it in a directory in the filesystem. Perhaps the Pis could cap...
by MarkR
Mon Feb 11, 2019 10:12 am
Forum: Automation, sensing and robotics
Topic: Servo jitter and GPIO 29(??)
Replies: 10
Views: 759

Re: Servo jitter and GPIO 29(??)

You will need to check, with an oscilloscope, the exact pulse behaviour. I have seen, previously, in my own robots, that changing the pulse width *can*, in some circumstances, cause a short pulse to be emitted. It is unclear whether this is a bug in pigpio. What I guess might happen is that during c...
by MarkR
Wed Feb 06, 2019 11:33 am
Forum: Automation, sensing and robotics
Topic: Should I execute opencv on Pi, or send the vedio to the computer to deal with it?
Replies: 1
Views: 151

Re: Should I execute opencv on Pi, or send the vedio to the computer to deal with it?

It depends entirely on what you want to do with opencv. You should try creating a prototype of the code and measure its performance on the Pi. The Pi is likely to perform much worse than e.g. a desktop PC; I am fairly sure that you can't use the Pi's GPU for any of the GPU-accelerated algorithms. BU...
by MarkR
Tue Feb 05, 2019 12:11 pm
Forum: Automation, sensing and robotics
Topic: Seeking guidance with powering motors
Replies: 19
Views: 987

Re: Seeking guidance with powering motors

I don't know how big your system is, but I suggest using the N20 gear motors which are tiny, cheap, and have amazing metal gearboxes available at loads of different ratios. Hint: Search the usual sources for "N20 gear motor" As far as driver is concerned - it's much easier to use a readily made moto...
by MarkR
Fri Jan 25, 2019 5:04 pm
Forum: Automation, sensing and robotics
Topic: Raspberry Pi 3 Robot car, Good to go?
Replies: 5
Views: 778

Re: Raspberry Pi 3 Robot car, Good to go?

You don't need a motor controller, as servos have these built in. There are many variations (and huge amount of clones) of the MG995 servo. I bought a few "continuous rotation" models from some Chinese site and they seem to work ok on 5v from a power bank, plus servo pulses from a Raspberry Pi. You ...

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