Lair Of The Multimedia Guru

November 4, 2018

Silencing an oil-filled radiator

The way oil radiators work is that the oil inside is heated by electricity flowing through some resistive heating element. The heated up oil then raises due to lower density and that way circulates in the radiator which then gets hot and heats the air.
Noise is produced by either mechanical thermostats or relays, so every time the set temperature is exceeded by some fixed amount some mechanical switch or relay switches which makes a click. That can be annoying if one tries to use a device like this in an otherwise silent bed room.
The Device:

To get it open one has to remove 2 screws and slide teh front down:

The top can be removed too after that and after removing the handle.

Three more screws later the next front layer can be taken off, that is as much as we need to disassemble to access all parts we need to access:

Removing the lower board is trivial, just remove screws and disconnect cables:

Next the 2 noisy relays are desoldered:

To replace the relays 2 solid state relays from ali express are added, they are rated at several times the needed current (i expected the rating to be exaggerated when i ordered and wanted to make sure they arent underrated but it seems the seller actually was honest with the rating). Careful attention is also paid to their heat-sinking requirement (which is none at the currents they would be used with).

And a quick tests shows they are working fine and also have a pretty red led indicating that they are on:
btw, they are lacking their top cover because the heater could not be closed with it on, and it serves no purpose in this case

And now i have a silent electric oil heater radiator thing … click …WTF
Was there some part expanding from the heat and making a noise ? something on the 2nd board i didnt look at ?
I had it already reassembled and had to disassemble it again to trace where that came from. The radiator is rated for 2000W, one circuit 700 W or so and the other the rest to get to 2000W. It contains a fixed mechanical thermostat that disables both heating elements in case of overheat. and the 1300W heater has its own mechanical thermostat which disables just it at 85°C. The surprising thing here (to me) was that 85°C is easily exceeded by the 700W element alone. So the heater rating of 2000W is misleading at best because the heater under normal conditions will only heat with the 700W element continuously. The 2000W will just be used for a short period. After learning about that ive checked the shop where it was bought long ago and looking at heaters rated at 700W (which they have too and which are smaller) one quickly finds customer complaints that the 700W units switch off and are unable to sustain heating at 700W. This is Europa not China :( I did not expect to find this …
Ok back to the silencing, the solution here is in fact very simple. As the 2000W and 1300W modes are fake and only sustain 700W anyway and i have to assume for a good reason. The solution is to simply disable the 1300W part.

With that change the radiator is now actually silent and also looks cooler with the relay led shining through the front. Looking at the images i regret a bit that i hadnt thought about replacing the front by a transparent polycarbonate window. it would have looked cooler ;)

Filed under: Electronics,Off Topic — Michael @ 23:04

October 6, 2018

Pandaboard 5v power supply

A few days ago i noticed that my panda-board died. This is one of the 2 ARM systems on fate.ffmpeg.org.
Resetting or unplugging and re-plugging did not help. Replacing the power supply with a random 5v supply made it come back to life.
The failed power supply is a HNP-24-050 “HN Power Germany”. This is now probably the 3rd or 4th failed power supply for my panda board. The one its running on currently is a random one from ali-express. I must say iam really disappointed by the trash that some german electronic shops sell. All the failed power supplies where bought from germany, not china. The failed supply still produces 5v but when subjected to the slightest load its output collapses to 0, even 200mA is too much.
Ive read on the net that some digikey supply is recommended but both part numbers i found are marked obsolete.
Anyone has any recommendations ? I am not too positive that the 2€ +free shipping supply its running on currently will last very long.
I know i can just run it off a brand name ATX supply or a bench supply but that is a bit inconvenient.
Also if anyone wants to add more ARM hardware to fate.ffmpeg.org, so we have a bit more redundancy, thats certainly welcome

Filed under: FFmpeg,Hardware — Michael @ 23:41

September 20, 2018

Testing high voltages

The chinese negative ion generator i used in 3d-printer-particles-air-pollution made me a bit curious about what voltage it outputs. The page from the seller mentions several different values, 2-5kv, 5-8kv, 5kv and other things. So one wonders what it actually is. This sadly cannot be directly tested by just using a normal DMM as its a bit outside the supported voltage range of the average DMM. High voltage probes for DMMs exist but even chinese ones seem to cost at least ~70€ and i wouldn’t trust them safety wise. So lets make one for 1€ which we can trust to be unsafe.
We start out with a inappropriate high voltage probe enclosure, which we disassemble and remove the unneeded parts:

The innards of our HV probe is simply a 90MΩ resistor, which will together with the internal 10MΩ resistance of the DMM form a 10:1 voltage divider, extending its input range.

Lets try:

1470V, hmm
Checking what output saftey resistance this device uses:

It seems its something around 20MΩ, maybe 2 10MΩ resistors ? Its potted so no easy way to tell exactly. But this changes our output voltage estimate as now our probe effectively is 110MΩ instead of 90MΩ. That raises it to 1764V, but it still feels a bit lowish to me. Also the 120MΩ to ground would draw 15uA, which could pull the voltage down by an unknown amount. This ionizer thing after all is not intended for producing any current.
To test for this we can use a higher value resistor. I do have a 1GΩ resistor (though it cost more than 1€), with it we get:

Aha, 4270V, so the 15uA does in deed quite significantly pull the voltage down. Now with 1GΩ we still pull 4uA here so this is likely still a too low estimate. Sadly i do not have a higher value resistor ATM.
What remains is to check that the 2 HV probe setups actually work at all, we must test this as we cannot be sure the DMM behaves as expected in this setup.

Both produce expected values at a 1kV test input, the voltage appears to be slightly below 1kV though.

at a 500V test input the value matches much better indicating that indeed the 1kV test output seems lowish

disclaimer: high voltage is dangerous, do not play with it or replicate anything described above. If you do anyway you do so at your own risk.

Filed under: Electronics,Off Topic — Michael @ 10:39

September 10, 2018

Copyright EU #4

In 2 days (on 2018.09.12) The next vote on the copyright directive in the EU Parliament will occur.
Resources about the draft, which IIUC will be voted on are available on https://www.saveyourinternet.eu/resources/. If you live in the EU and feel that this proposal is bad you can use https://saveyourinternet.eu/ to contact your representatives.
There are also 252 proposed amendments, iam not sure these will be voted on or not (i thought they would but the timeline seems too tight to really do that).
Also there will be EU parliament elections in a few months. If you live in the EU and care about this, check how the parties voted on this directive and other directives that may affect you before you vote on who you want in parliament. Politicians of all parties are very dishonest, only by looking at past actions can one with any accuracy predict what they will actually represent. No politician would ever say they intend to vote in a way that the audience of the moment dislikes.

Filed under: Uncategorized — Michael @ 18:04

September 9, 2018

3D printer particles / air pollution part2

When i experimented with measuring the amount of particles from my 3d printer, i noticed the majority originated from when the heat-bed was turned on. I had cleaned the inside of the printer roughly before, so this was slightly odd. More investigation shortly later revealed the cause though.


The use of tinned multi-core wire without ferrules. Why it was done this way you may ask? Because between the incomplete and poor official documentation, the consumer made videos of how to assemble it and my plain lack of knowledge about how multi-core wire with and without solder behaves in this case. This way of connecting the wires seemed sound enough and there also where no ferrules included with the printer kit.
That said if you did connect high current wires in a similar fashion, you probably want to consider redoing it with ferrules or in another reliable way, like directly soldering to the board or soldering a solid core wire onto the multi-core as an intermediate. Also keep in mind iam a programmer not a expert for this so do your own research if failure of a connection could have some real consequences.
My printer is fine, the heat-bed also didn’t behave erratically or anything. And i never trust/trusted it anyway in terms of safety to ever run it without someone being at home, so in my case it was impossible for this to cause any real harm. But i still didn’t expect that …

I didn’t had any fitting ferrules, so the way i fixed it was to take some terminal connector thingies, which when one cuts half of each off are basically ferrules. I also didn’t had a new terminal block that was rated for enough amps to replace the roasted one. I will properly replace these once i have proper replacement and have time. Quite likely next time that printer needs some kind of “service”.

Filed under: 3D printer,Electronics — Michael @ 17:09

July 31, 2018

3D printer particles / air pollution

A while ago i read about 3D printers spewing out nano-particles into the air, especially ABS. I was curious if i can actually measure this on my own printer and how to fix it.
My plan was to use a cheap air quality detector, that i bought previously. It has to be noted here that the device detects particles 300nm and larger while what i read seems more about 100nm and smaller particles so its not 1:1 comparable.
Before anything i used my vacuum cleaner to very roughly remove large visible crap from the inside of the printer enclosure.

First baseline measurement, with the printer on, no heating yet.


Can we reduce that particles/dust ? Lets try properly cleaning the enclosure with the vacuum cleanerto use a stream of negative ions to ionize the particles, so it sticks to something and doesnt stay in the air. As can be seen this is a effective way to clean the air, or the measurement device is affected by the ions.


There is a slight disadvantage, in that it seems the well designed printer (which lacks grounded components). Has its metal frame charged up by the ions and that then eventually discharges into something …


Luckily no permanent damage is done and a reboot of the printer clears this. Until it quickly happens again. But after a few minutes all the particles appear to be eliminated


Adding a wire between ground and the frame (with a 1k resistor between) stops it from charging up and seems to resolve this problem.


Next after heating up the heatbed to 65°C without the ions. There is really alot of particles/dust in the air of the enclosure:


After also heating up the nozzle to 215°C with PLA in it:


After finishing the print 38 minutes later


Waiting 30min (the heatbed is not disabled by the printer, the nozzle cools down), there are still significant particles in the air


Switching the negative ion generator on, 5 minutes later the particles in the air have decreased significantly


Another 5 minutes later the particles are largely gone


Now question, what happens if we try to print with the thing on?
First opening the printers enclosure brings some of our particles/dust back (from the airflow caused by the door presumably). After all it didnt magically disappear and theres nothing that would truly capture it (the heatbed is at 65°C here)


After the nozzle heated back up to 215°C the particles actually decreased


Taking an image every minute from the air quality meter shows that within about 6 minutes after the print started the particles go to 0, it does rebound slightly and fluctuate around 0 after that.


The print finishes without problems after 36 minutes. Originally i intended to repeat this with other filaments but as the biggest dust/particle creator seems the heatbed or rather air convection from its heat. This would need to be setup differently to eliminate that. As it drowns out new particles from the heated filament. But still this shows that for less than 4 euro shipped one can get a device to eliminate at least larger particles from the air within the enclosure of a 3d printer. Compared to a filter this is probably easier to setup as well. Further experimentation would definitely make sense. Though simply having an enclosure and opening it together with a window for 5 minutes probably removes most particles, if one is concerned about it.

Filed under: 3D printer — Michael @ 21:04

July 14, 2018

Chinese worklight repair

A while ago i bought a quite cheap flashlight/”worklight” from aliexpress. Not the best quality but it worked.

About 3 days later its button started to work only intermittently. A few days later it basically didnt work anymore.
I wonder why these items have so many 5 star reviews.
Yesterday after putting some food in the oven in the morning i had some time while waiting for it.
After disassembly, it looks like this:

The button is a standard SMD button, i had some equivalent replacement.

After exchanging it, it works again. Lets see for how long …

Almost forgot, the failed button after gentle disassembly:

Filed under: Electronics,Off Topic — Michael @ 22:14

July 7, 2018

Copyright EU #3

The EU Parliament has rejected to fast track, (that is to pass it a few days ago) the controversial directive. IIUC it can now be modified by politicians and will be voted on again in September. Parliament debate and vote from 5th july 2018 (note this has subtitles if you do not understand the MEP who speaks in his native language).
If you care about this, you probably want to stay active and keep an eye on how this unfolds.
Also for those not seeing the problem, think about just sites like wikipedia and how exactly upload filtering (that costs money) or some link tax would work for them. Or how free software projects like FFmpeg could run a bug tracker where people upload small samples of media files which trigger bugs. Of course who and what this directive might affect depends on the very fine details how it is worded and also how the actual implementations in law in each European country will be worded.

Filed under: Off Topic — Michael @ 11:04

June 22, 2018

Copyright EU #2

2 days ago the EU JURI committee voted in favor of the controversial art 11 and 13 of the copyright directive. This was not totally unexpected. Next the whole EU parliament will vote on this so theres still a chance to talk to your representative, if you care. If that fails too, the next EU election is 2019, that is next year. The relative closeness of the next election may improve chances for politicians to care about what the consumers and companies they are supposed to represent want. Iam also still wondering who actually benefits from this law. I thought lawyers would but it seems even some lawyers don’t like it. If you speak german heres a video from a german lawyer about this.

Filed under: Off Topic — Michael @ 11:03

June 16, 2018

Copyright, EU

In 3 days, the EU JURI committee will vote on the copyright directive. If you live in the EU (and under a rock and are unaware of this). Then you may want to look at what this is about and potentially contact your representative member of parliament.

Below is some unrelated rant/chatter about copyright, please ignore if this doesn’t interest you.

Looking at the state of copyright and how it changed, over teh decades makes me a bit sad. Iam no lawyer and only know things roughly not detailedly but. The long term trend of more rules, more restrictions, heavier penalties. Its really a slap in the face of the consumer, the companies between and i would argue also the content creator.
Now why is all this which seems so great for content creators at the surface actually not. First, all the extra regulations we already have and the potential future ones we might get, require substantial resources, time, human, financial and technical to follow. They must come from somewhere and it is from money that is taken out of the consumer -> content creator chain. Do these laws produce more paying consumers than they add cost?

And then theres a completely separate thing. Why in a world of democracies, that is places ruled by the people do we pay those who restrict content and knowledge while we do not pay those who give content and knowledge away freely to everyone?
Hundreds of years ago it was impossible to give information/content/knowledge/music/films away for free to everyone. Because the paper for a book, the musicians turning written notes into audio all cost resources. It made sense to pass some money from the act of copying which was expensive to the content creator, the copyright owner. But today where the act of duplication is essentially free still doing this is simply insane. Its restricting who has access to basically public content without anyone having any real gain from it.

You could look at it like this also: Someone creates the worlds best operating system and gives it away for free to everyone, allowing everyone to change, adapt and improve it. Maybe billions of people use it daily, surely the governments who collect trillions of tax $ would pay him and the people who also worked on it something for the public service they did ?
OTOH, large and rich groups managing content/information/knowledge/designs/…, restrict it very heavily using every law, regulation and trick. And surely our politicians who represent us, the people of this planet would make laws that require these groups to make their content/information/knowledge/designs/… available for everyone before they could legally be allowed to collect payment?

Maybe the thoughts above, especially the 2nd are too extreme, too radical, i dont know. And no question this view is over simplified. But i cant see how the direction, in which the copyright law is moving, helps anyone except maybe lawyers. And at some point, heck maybe even lawyers will be against this…
Ironically, IMO even the movie industry would financially benefit from a change. There are surely many possibilities, one would be
Find out how many people watch/use public domain content (these statistics are already known) pay the content creator from taxes in a way thats related to how much her content is used.
With this there would be no need for any restrictions, and no motive for piracy. It would eliminate all copyright infringement of that content, all resources for dealing with regulations or violations. Thats alot of resources that are not wasted and thus there would be more left for the content creators.
Compare this to all the laws and regulations we have and which are planned, none of which will make any difference to piracy and copyright infringement.
Of course in reality its more complex than this, but personally from my view from under my rock, it seems the old style copyright is slowly being replaced by new systems even with all the apparent efforts from our politicans to prevent it.
For example i have not watched any “hollywood” movies since many years, in fact i also have not watched any “classical” TV. Simply because there are so many content creators today who happily give their content away for some ad based payment or for free. Basically unrestricted. One can watch what one wants, when one wants and how one wants. Also the breath of content to choose from is many orders of magnitude larger in the “basically free” segment than the restricted.

Filed under: Off Topic — Michael @ 23:44
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