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controlling motor with PWM?

Stack All Flow — Mon, 28 Mar 2022 03:47:12 +0000

I am using a RCS-Model-M2313 R/C Servo and I have managed to create a PWM. My problem is that my motor doesn’t react as I was expecting. I would like to control the motor angle with the duty cycle but it doesn’t work.

Indeed, with a 28% duty cycle, a 550 Hz frequency, 1.7V offset, a 3.3V signal from my MCU I can control it to come back to the same position. I have powered the servo with a 3.7 tension.

When I change the duty cycle, the motor turn but doesn’t stop anymore.

The datasheet doesn’t give any information, I really need your advices.

Thank you.

Regards,

Mattew

Accepted Answer:

Your frequency is way too high, or conversely, you are not waiting long enough between pulses. You should be sending a 1 to 2 ms pulse every 20 to 50 ms. Note that this means 50 Hz maximum.

Also, your “1.7 V offset” makes no sense. These pulses should generally be 0 to 5 V digital signals. I followed the link you provided, but that only goes to a product sell page not a datasheet, so we can’t tell exactly what voltage levels the digital signal must be. When in doubt with hobby servo units, use 5 V logic.

Try a 1 ms pulse every 20 ms. That should send the arm to one end. Then try 2 ms every 20 ms. That should send the arm to the other end. Try it with the 3.3 V signal straight out of your processor and see if that works. If it doesn’t, make it a 0-5 V signal instead. That really should work if everything else is hooked up right. If you don’t have a level translator chip, you can rig up something with a NPN transistor and pullup resistor. That will invert, but just invert the processor output to compensate. A HCT (note the T) logic gate powered at 5 V can also be used as a 3.3 V to 5 V converter.

Are you sure the processor power is properly filtered so that the current spikes the motor draws doesn’t effect it? A schematic and scope traces with a clear description of what happens in each case would help a lot.

Electronic #controlling #motor #PWM

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arduino – Does it make sense to plot the angle in an signal spectrum analyzer?

Stack All Flow — Mon, 28 Mar 2022 03:37:49 +0000

I’ve built a toy oscilloscope with an Arduino, acquiring the samples with the ADC and plotting the spectrum on my computer. The spectrum is the output of the FFT algorithm. You can see a video here of the program in action.

The yellow line is the actual value of each sample as the output from the Arduino’s ADC. The red line is the magnitude of each complex number as the output from the FFT function, and the green plot is the angle of each of those complex numbers. The first spike is noise from the AC main power line, which is 50 Hz.

The red plot shows the “energy” of each frequency. What information does the angle shows? Is there an intuitive explanation?

Accepted Answer:

In this case, the absolute angle you are plotting is relative to the phase at which you are taking samples with your ADC. By the way, it looks like your sample rate isn’t very stable, judging from how much the speed of the waveform moving across the display varies.

It would probably be more useful if you were to provide a triggering function for your oscilloscope, so that you get a stable waveform display to begin with, and then display relative phase, perhaps taking the phase of the largest magnitude peak as your “zero” reference angle.

Keep in mind that the phase information in FFT bins that have low magnitude values is mostly the result of low-level noise, and won’t be very relevant to the overall signal analysis.

Electronic #arduino #sense #plot #angle #signal #spectrum #analyzer

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How to display SMD footprints in Eagle CAD as separate layer instead TOP or BOTTOM?

Stack All Flow — Mon, 28 Mar 2022 03:27:39 +0000

I would like to print Pads, Vias, SMD footprints altogether so that I can apply UV solder mask on board. The problem is that the SMD footprints is part of TOP layer.

What to do?

Looks like correct layer would be tStop, but it appears stripped instead of filled. Looks like I should use some image editing software to fill those pads manually.. .

Accepted Answer:

As the others have pointed out, the correct layer to use for solder mask are tStop and bStop.

In many cases these layers are visualised in Eagle as hatched lines which is not what you want for printing. However it is very easy to remove this and print them out as solid. Simply check the Solid option in the print dialog:

Electronic #display #SMD #footprints #Eagle #CAD #separate #layer #TOP #BOTTOM

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Thermo Electric Can Heater / Cooler Heating vs Cooling Speed?

Stack All Flow — Mon, 28 Mar 2022 03:17:39 +0000

I recently purchased a cheap (~$25) 36W thermoelectric cup holder designed to heat or cool a soda can sized object. It works very quickly for cooling and draws about 3A at 12V. For heating, it heats about 4 times slower and draws only about 0.7A. The fan only runs when it is in cooling mode. According to the vendor, it is not unusual for it to heat slower than it cools, and it is normal for the fan not to run in heating mode.

The lack of fan and lower current in heating mode leads me to believe that either it is not using the TEC for heating mode, or that for some reason it only runs the heating mode at 1/4 the TEC capacity.

Is there any reason why it would be advantageous to add a separate resistance heater or to run the TEC at 1/4 capacity without the fan for heating purposes? It seems that it would be best to have it heat something as quickly as it cools it by just changing the direction of the current in heating mode.

Eventually I will probably take it apart to see what it is really doing.

Accepted Answer:

It takes more energy to get from room temperature to hot drink temperature than it does to get from room temperature to cold drink temperature, so given the same thermal transfer rate, heating a drink will take longer to begin with.

Peltiers are pretty cool things. The difference between performance in heating and cooling mode likely has to do with several factors. Peltiers have fairly strongly defined optimal operating currents.

At too low a current, the thermal conduction losses of the peltier will dominate, determined by thermal conductivity and temperature differential along with convection as the interior grid of the peltier is likely not insulated.

At too high a current, the heat the peltier produces due to $I^2R$ losses through the little bismuth cubes will dominate.

Used as a cooling element, a peltier is a relatively inferior device in terms of efficiency but gets used because of the lack of moving parts, tiny form factor and electrical versatility.

Look at the way it operates in cooling mode. The heat is pumped out of the cold side of the peltier and into the hot side heatsink. The cooler you keep the hot side of the peltier, the better your efficiency will be. The hotter the heat sink gets, the more difference there will be between its temperature and ambient, and the more heat will be shed into a given volume of air. Note that all losses in the system will contribute to higher heatsink temperature. In this mode there is great value to moving air across the heatsink.

Used as a heating element, a peltier has the very special property of offering better than 100% electrical heating efficiency. You don’t have to pay for all of the watts of heat with watts of electricity, but it does have to come from somewhere. I’m guessing this is where they’ve gone with having the device work slower in heating mode. They are avoiding the efficiency losses with using the fan (temperature differential between heatsink and ambient will be smaller in heating mode than in cooling mode and all thermal losses in the system will decrease the temperature differential and therefore decrease the value of using the fan. With a resistive heating element added, you would be able to trade off efficiency to heat the liquid more quickly.

As a final thought, in heating mode, the colder the cold side becomes, the greater the temperature differential over the peltier becomes without the liquid inside the device having to change temperature at all. The total heating ability of the peltier alone is limited to its own losses plus available external thermal energy. They are not incredibly durable devices, being composed of hard ceramic and somewhat brittle metal cubes and they are not immune to the thermal stresses from the differentials they create over themselves. The current the device operates at in heating mode may minimize these stresses, and using a resistive heater would allow the stresses to be minimized by having the heat that otherwise must be produced by losses that could be stressing the peltier produced elsewhere. On the other hand if the heatsink was shielded, you could attempt to drive it far enough below ambient to make using the fan worthwhile to speed up a portion of the heating sequence at a still-higher-than-100% electrical efficiency at risk of stressing the peltier. If you are going to use high temperature differentials, good practice is to cut grooves partway through the ceramic plates in a grid so that if the plate cracks it will crack along these lines. The grooves should be aligned between bismuth cubes and as much as possible not cross copper plates on the side being cut.

Electronic #Thermo #Electric #Heater #Cooler #Heating #Cooling #Speed

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Disable smooth fading when changing brightness of MacBook Pro Screen?

Stack All Flow — Tue, 01 Mar 2022 22:32:14 +0000

I’m on a late 2013 15″ MacBook Pro with Retina Display.

Is there any way of disabling/enabling whether the display smoothly fades when the brightness keys are hit (F1 to lower, F1 to raise)? On my old computer, a late 2008 MacBook, it just snapped to the new brightness if I changed it in system preferences or used the Function Keys shortcut.

I want to do this because I am in a small theatre, and when I run light cues off my computer that black out the stage, I want it to snap to near-zero brightness, as opposed to the higher brightness I need to have it set to when the lights are up to prevent the screen from being washed out. I am setting the brightness via applescript.

Accepted Answer:

Disable #smooth #fading #changing #brightness #MacBook #Pro #Screen

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IMac that slow – is that normal?

Stack All Flow — Tue, 01 Mar 2022 22:22:18 +0000

I have a iMac Retina4K from the end of 2015 with 3.1GHz Quad-Core i5 and 8GB DDR3 on 21″ with a second monitor attached, and a HDD-disk. macOS is Catalina and I am running Firefox, Adobe InDesign and Adobe Illustrator most of the time. Since I upgraded to Catalina my Mac is soooo slow that starting up in the morning until anything really runs (i.e. I am able to click on an app) takes up to 10 minutes with no applications opened yet.

Opening up Illustrator works in 6 of 10 times, else it just freezes. If opened it does work okay though. Firefox freezes also on a regular basis. I never open up more then 3 applications at the same time, have no widget etc running and I got hundreds of gigabyte diskspace left.

I get it, that this isn’t the newest device but shouldn’t the OS and some really simple task like opening up a browser be “there” in less then 5 minutes?

My question though is a different one: If I’d set up/reinstall the Mac completely new with Catalina (as I am bound by Creative Cloud to it) should that speed up my described routine or is the current scenario just what I can expect from the combination of that hardware/software combination?

Accepted Answer:

You can use Activity Monitor (in /Applications/Utilities) to see what processes are taking the most CPU and Memory, and monitor disk input and output. This may help to identify what is causing the slowness.

However, the most likely cause (in the absence of any other info) is the presence of an internal mechanical hard drive, either by itself or as part of a ‘Fusion’ drive.

Mechanical hard drives are much slower than modern ‘solid state’ SSDs. If your Mac has to ‘swap’ memory data to and from the disk, then this will slow things down dramatically. Also, the drive is at the end of its useful lifespan, and may show signs of failing.

While taking an iMac apart to replace the drive may be of moderate difficulty, you would do better to use an external SSD. Old Thunderbolt 2 enclosure are harder to find these days, but even a USB3 SSD will be faster.

Apple continued to install hard drives in iMacs for many years after it was using SSDs in its other Macs. So, in reply to the question ‘is this normal for an iMac’, the answer is sadly, yes.

IMac #slow #normal

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IMac SSD upgrade – Firmware password lock?

Stack All Flow — Tue, 01 Mar 2022 22:12:32 +0000

My dad bought a used 21.5 iMac (2017) a few weeks back (previous owner bought it new but decided to sell after a week, so its basically new.) Given that it came with a 1TB fusion drive, we decided to switch it for the Samsung EVO he was using in his previous Macbook (He doesn’t need storage, only speed.)

All went according to plan in terms of opening and swapping the drives, but upon rebooting (attempting to ctrl+r to boot menu) it popped the apple logo and then swapped to a black screen with a lock and password field.

After a little reading on the subject it seems someone must have enabled the EFI Firmware password protection which doesn’t allow booting on other drives e.g. external or otherwise.

I’ve contacted the previous owner, but she’s drawing a blank, claiming never setting up anything of the sort. I’m unsure if this can be enabled during first boot installation, but she didn’t strike me as the type who would know how to do so afterwards (let alone think about it.) My guess is that the shop might’ve had it returned from a prior owner, not reset it correctly and resold it as new (or perhaps discounted, hard to tell from the receipt.)

TL;DR

Knowing firmware is locked with an unobtainable password …

Would I be able to remove the new SSD and insert the original HDD and have the password prompt go away? Or is the system locked until correct password is entered, no matter the drive (it booted prior to switching drives).
Warranty void on opening and swapping diskdrive? Searching around it seems everyone has a different story. Some say the rest of the system is still under warranty, others do not. This isn’t Apples issue of cause, but I would likely levy it against the reseller.
Even if the old HDD would work again, I’m assuming that not having the FW password would be a roadblock if reinstalling OSX in the future?

Accepted Answer:

This Apple document tells you everything you need to know about Firmware passwords.

The essential points for you are:

Your Mac asks for the firmware password only when attempting to start up from a storage device other than the one selected in Startup Disk preferences, or when starting up from macOS Recovery.
If you can’t remember your firmware password or passcode, schedule an in-person service appointment with an Apple Store or Apple Authorized Service Provider. Bring your Mac to the appointment, and bring your original receipt or invoice as proof of purchase.

The Firmware password is not required for OS installation.

You will need to ask the original purchaser for their receipt or other proof of purchase.

IMac #SSD #upgrade #Firmware #password #lock

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IPhone – How to view (not download) iPhone pictures on a Mac screen?

Stack All Flow — Tue, 01 Mar 2022 22:02:18 +0000

I have an iPhone 5 with various photos.

I have a Mac desktop running OS X Yosemite.

Is there a way to view a fullscreen slideshow of the photos on the Mac display? I don’t want to download the photos, just flip through them for display on the big screen.

Accepted Answer:

Apple’s mandated solution would be to wait for the photos to upload to your Photo Stream or iCloud Photo Library, then start a slideshow in iPhoto or Aperture.

Alternatively, you could make your Mac into an AirPlay receiver using a 3rd party app such as AirSquirrel’s Reflector. This one is paid, but I’m not aware of any free equivalent.

IPhone #view #download #iPhone #pictures #Mac #screen

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Eclipse Not Working in 16.04 in Ubuntu?

Stack All Flow — Wed, 15 Dec 2021 19:15:00 +0000

6.04eclipse

Eclipse was working as good as anything on 14.04. I did a clean install of 16.04 and installed Eclipse. But it runs a Java program only once after which it just hangs during subsequent attempts before I remove and reinstall it. I have tried many things, since in the beginning I needed CDT as well. Right now, I just want to remove everything related to eclipse and do a fresh install (remove all the configs and dependencies). Please note that I used Eclipse installer to install Eclipse and the eclipse icon image is also not appearing (the default ubuntu ? is appearing).

Accepted Answer

I had something the same with 16.04 and Eclipse Mars. I thought it had frozen but in fact it was running very, very slowly. The problem is the version of GTK+ 3, shipped with 16.04. Fortunately the solution is very easy. Open a terminal and then type export SWT_GTK3=0, then start Eclipse from the terminal. If that works, then a more persistent fix is to put the 2 lines below, as they appear in your eclipse.ini:

--launcher.GTK_version
2

before the line:

--launcher.appendVmargs

The bug is filed with Ubuntu at bug 1552764

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Is It Okay to Delete the ~/.Cache Folder in Ubuntu?

Stack All Flow — Wed, 15 Dec 2021 18:15:00 +0000

cachehome-directory

When I use disk usage analyzer and scan my home folder, the .cache folder in my home directory always shows up with a decent bit of things in it.

Would it be okay for me to delete the contents of this folder or would it damage something?

Accepted Answer

To answer the question, IMO you can delete all of .cache with no long term detrimental effects.

If your .cache is growing large, it might be better to look at the contents and determine what application is making it large and re-configure a bad acting application (rather than simply deleting .cache when it grows too large).

Another directory that can take up a lot of space (and/or save an embarrassing bit of evidence) is the .thumbs directory. Many files in .thumbs seem to be duplicates.

To clean (just take care with the -rf flag and other directories

rm -rf ~/.thumbs/*

When you are new to Ubuntu/Linux it is hard to know what you can and can not delete in your home directory. For the most part you can delete most anything in your home directory, programs or applications that require .cache (or other dot files such as .local) will re-create them.

Most of the time, at worst, you will lose custom configurations, but no real harm to the system.

I would not advise you start a habit of deleting things you do not understand in your home directory, back it up or use a test account. If in doubt, the safe thing would be to make a back up or move the file.

mv .cache .cache_backup

You can then restore from backup if needed.

Definitely do NOT start deleting things you do not understand outside of your home directory.

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How to Set up Live Audio Streams to a Dlna Compliant Device in Ubuntu?

Stack All Flow — Wed, 15 Dec 2021 16:53:00 +0000

dlnapulseaudiorygelstreamingupnp

Is there a way to stream the live output of the soundcard from our 12.04.1 LTS amd64 desktop to a DLNA-compliant external device in our network? Selecting media content in shared directories using Rygel, miniDLNA, and uShare is always fine – but so far we completely failed to get a live audio stream to a client via DLNA.

Pulseaudio claims to have a DLNA/UPnP media server that together with Rygel is supposed to do just this. But we were unable to get it running.

We followed the steps outlined in live.gnome.org, this answer here, and also in another similar guide.

In 12.04 LTS we can select the local audio device, or our GST-Launch stream in the DLNA client but Rygel displays the following message and the client states it reached the end of the playlist:

(rygel:7380): Rygel-WARNING **: rygel-http-request.vala:97: Invalid seek request

There was no way to listen to live audio streams on the client.

Only after a distribution upgrade to 14.04 LTS we were able to select a live stream on our DLNA renderers from settings nicely outlined in below answer. Still, we needed to select an established stream after we started rygel and were unable to push a new stream to our UPnP devices. Audio metadata were not transmitted.

Are there any other alternatives for sending the audio of our soundcard as live stream to a DLNA client?

Accepted Answer

Pulseaudio-DLNA

I created a little server which discovers all upnp renderers in your network and adds them as sinks to pulseaudio. So you can control every application via pavucontrol to play on your upnp devices.

That’s the kind of comfort I always wanted when dealing with upnp devices under linux.

The application can be installed from source or DEB package downloadable from git, or after we had added the project’s official ppa:qos/pulseaudio-dlna to our sources with:

sudo apt-get update && sudo apt-get install pulseaudio-dlna

We then run pulseaudio-dlna from the command line with following options:

pulseaudio-dlna [--host <host>] [--port <port>] [--encoder <encoder>] [--renderer-urls <urls>] [--debug]
pulseaudio-dlna [-h | --help | --version]

See also the pulseaudio-dlna “About” for more.

When there was a DLNA renderer present we can then select it from the sound menu as an output sink:

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Natural Sounding Text to Speech in Ubuntu?

Stack All Flow — Wed, 15 Dec 2021 15:53:00 +0000

software-recommendationtext to speech

I am looking for some easy to install text to speech software for Ubuntu that sounds natural. I’ve installed Festival, Gespeaker, etc., but nothing sounds very natural. All very synthetic and hard to understand.

Any recommendations out there?

Accepted Answer

SVOX pico2wave

A very minimalistic TTS, a better sounding than espeak or mbrola (to my mind). Some information here.

I don’t understand why pico2wave is, compared to espeak or mbrola, rarely discussed. It’s small, but sounds really good (natural). Without modification you’ll hear a natural sounding female voice.

AND … compared to Mbrola, it recognise Units and speaks it the right way!

For example:

2°C → two degrees
2m → two meters
2kg → two kilograms

After installation I use it in a script:

#!/bin/bash
pico2wave -w=/tmp/test.wav "$1"
aplay /tmp/test.wav
rm /tmp/test.wav

Then run it with the desired text:

<scriptname>.sh "hello world"

or read the contents of an entire file:

<scriptname>.sh "$(cat <filename>)"

That’s all to have a lightweight, stable working TTS on Ubuntu.

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