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

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

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

November 5, 2017

Genetics history

Maybe a little off topic. But if one looks at DNA sequencing technology, in 2001 sequencing one humans genome cost 100 million USD, in 2015 it was down to slightly above 1000 USD. Today in 2017 you can buy a new DNA sequencer the size of a mobile phone for 1000 USD. Considering this, humankind today basically has the technology to sequence every human genome.
If someone asked me 10 years ago, what one can do about inherited genetic diseases or any thing else genetic. I would have said, wait 200 years till we have molecular-nano-technology and hope WW3 doesn’t happen. But in 2015 Chinese researchers edited human genes in embryos with some success. But still thats basically individual cells in a lab not an adult made of 1013 cells. But in fact similar methods have already been used and demonstrated to also work with individual organs in vivo in adult mice (not sure who did this first or when, but google finds quite a few things). And what i read few days ago according to interim results, non human primates, editing over 20% of liver cells successfully after a single dose and no adverse events with multiple dosing.
Now one wonders a bit, if one extrapolates this, where this tech will be in 5, 10 or 20 years. I think the next decades will be very interesting in this area.

Filed under: Off Topic — Michael @ 0:41

December 2, 2016

Printing on metal and glass

A while ago i had the “need” to make a non removable “no advertisements” “sticker. To do that i tried several different methods to print on and etch metal. The methods where roughly based on various youtube videos for making other things. Its a while ago so i hope i dont misremember the details, i should have written this immedeately…
All the methods start out with a laser printer and then transfer the toner onto the object as a mask for etching.

Cold toner transfer

The image to be transferred is printed on normal paper. the object its intended to be transferred to is placed flat on a table and is wetted with a mix of ethanol and acetone something like 8:5 vol. Pure ethanol will do nothing, pure acetone will smear the toner. Then the printout is placed on top avoiding air bubbles and some timespan like 20sec is waited for the toner to soften. Next the printout is firmly pressed by some means (i used 2 pieces of wood and clamps) for some time (i waited 3 min). next the pressure is removed and one waits for it to fully dry. Next it is soaked in water for some time (3min in my case) and then with luck one can peel the paper off while the toner still sticks to the object one wants to transfer it too. Depending on the toner and paper different procedures are likely optimal. Using this to place a mask onto a piece of scrap aluminum worked so-so, some parts of the toner didnt like sticking on my first attempts. Also this method is only suitable for creating a mask for further processing, you would not want to use this to print onto metal as a final step as there is still paper sticking to the toner.

img_4807-small

Hot toner transfer

The image to be transferred is printed on “toner transfer paper” (from ebay). The object to be printed upon is heated to slightly above the melting point of the toner (likely around 100°C) (i used a kitchen hot plate). Its important to get the temperature approximately right, too hot and the paper will be burnt. Also IR thermometers do not work accurately on shiny metal surfaces. The paper is then placed on the hot object and pressed firmly onto it (i used a silicon tube with a glass rod in it rolling over the paper several times). Next the object is taken off the hot plate and let cool. When cool the paper is removed, the toner mostly sticks fine, some individual tiny holes may be present in the transferred toner. To ensure good adhesion i reheated the object to >50°C above the melting point of the toner.

Heres an example of the result of this method using the last piece of scrap aluminum i had laying around:
img_0714-small

Printing multiple times (if you can get the alignment right) or otherwise increasing the toner density improves the results of both methods. Also if there are defects, tiny holes or other you want to paint over them with something before etching. You also can apply some surface treatment like sanding or brushing to the metal before the toner transfer …

Etching

For the aluminum scrap pieces i had i used simple water and table salt as electrolyte, both anode and kathode where aluminum, separated by Plastic clothespins and held together by sticky tape. After several tries i learned that lower currents and voltages seem to work better. that is for the small piece i had something like 1.8V and i think 100mA for 2 hours. (Note, if you attempt to repeat this, you do so at your own risk, Electrolysis of water and table salt produces different things depending on the condition and electrode materials. Other electrolytes may be a better choice even though NaCl seems safe in this setup.)
After etching the toner mask needs to be cleaned off (unless it fell off already which it sometimes did and sometimes it stuck really
well) it can be removed with acetone or with patience also with other random things.

The electrodes with the cut up pieces of a clothespin and tape:
img_4806-small

The results of several attempts
img_0732-smallimg_0666-small

Transfer without etching

One can of course also skip the etching and keep the “mask” as the final result even with color or even as a addition to a previous etching step. This also works on glass (if you can heat and cool it without it shattering)

The results from my attempts for this:
img_0735-smallimg_0673_small

After this i had no scrap pieces of aluminum left nor really time and the problem i was trying to solve (someone repeatly removing my fathers no advertisement sticker from his mailbox … to collect more free coupons or paper … solved itself as she stopped)

Filed under: FFmpeg,Off Topic — Michael @ 14:37

May 12, 2016

Mobile phones for seniors

My grandmother has 2 mobile phones, both identical, they have an old style numeric keypad, tiny monochrome display. They are both old and look like they were used a lot, one works. The other sometimes works, there thus was need to obtain a new phone. Both phones she has have been bought by herself many years ago, they were phones intended for seniors and honestly they are just shit in every way IMO even when they were new, they are even hard and awkward to use for someone young.
I thus bought a cheap android phone for her, i was very curious if that would work out, she is 89 years old and AFAIK never used a computer or smart phone before. Going for a cheap phone that fits the requirements was done as this was quite experimental and i was not sure if she would loose the phone in a week or someone would steal it maybe. The phone needed a big battery as recharging had been a problem with her other 2 phones or possibly their batteries have aged too much.
The chosen phone was a cubot note s, 4150mAh 5.5inch IPS display 2/16gb mem, 4core, 3G, dual sim, dual cameras, … for less than 90euro. The 2 things the phone doesnt have is a notification LED and LTE support. Neither appeared important for the intended use.

On the software side, I installed

  • Big Launcher and configured it so everything one needs is on the home screen, like buttons for directly calling family members.
    I also tried Phonotto, necta and other launchers Phonotto seemed not to fully work with android 5.1, occasionally dropping one out of the dialer without ending the phone call, which made it not ok. I chose big launcher as i had to chose one and it seemed mostly ok
  • Missed call reminder, Which allows all kinds of vibration and led flash and screen on/off based notifications (due to missing notification LED on the phone) But even if it had a LED the bright LED flash and vibration should be better
  • Ultimate Caller ID Screen HD, With all extra buttons disabled and the the screen with just simple buttons for accepting a call and hanging up.
  • quick snap, as a simpler camera app but this wasn’t used sofar AFAIK
  • automate, Used for giving spoken low battery alerts at <30% and similar if the phone charging is interrupted before reaching 60%. Some testing though showed that it did not work reliable (it got stuck when there was no internet connection) and thus was not enabled when i gave the phone to my grandmother, we also were unsure about the notification activating in inappropriate situations

The above, i believe was the initial set of apps when i gave the phone to her, the biggest problem was surprisingly switching the phone on (the lockscreen was also entirely disabled), the button is basically invisible under the silicon protector thingy that comes with the phone. Some sticky patch cut into arrow shape stuck onto the phone helped though.
When we called her on the phone for the first time after leaving she did not succeed picking it up, even though she could do it when we where there after some tries. So it seemed a failed experiment, but a few days later and corrected volume settings she made multiple phone calls with it alone :)
Further improvements we did were, that we installed some software to lock the volume settings (cant remember its exact name, but there are multiple that do the job), the volume buttons are next to the power button. Disabling the “telephone answering machine” as it picks up too quick and only adds the problem of dealing with missed calls, which was a problem with her previous phones already.Call Auto Answer & ReadItToMe configured so it automatically picks up calls from family members after 10 seconds. And we also enabled speaker-phone by default. We also considered to install Gravity Screen – On/Off but as she managed to switch the phone on it seemed more a potential way to switch it on unintended.

One thing that kind of annoyed me alot while configuring things is finding apps that arent full of ads. It seems everything for android these days is either spyware, ad-ware, or costs money. I wish the play store would have a way to search for things that are good old free no hooks attached type of ware. But i guess google wouldnt like how they then would have to mark their own apps.

Also for the case of older people with little smart phone experience, a somewhat more integrated UI for android would be nice. Not needing to install a dozen things that might interact badly or that then dont work with the latest android version.
Something that when randomly shaking or pressing buttons on a phone in standby mode would display an arrow pointing to the power on button. Some reliable and unobtrusive low battery notification would be nice too, and that one not just for seniors, the dim red notification leds are kind of easy to miss. Some easy always available help button that can explain the available buttons/options on any screen, …

Filed under: Off Topic — Michael @ 2:00

January 11, 2016

Thermoelectric cooler

A while ago searching around on ebay for geeky/nerdy toys i found some Thermoelectric coolers/peltiers for around 2$ with free shipping. So i bought a few of them …
IMG_0474-small

They all worked fine, one had a hole in its silicon sealant though which ive “fixed” with hot glue (first heated the element up to reduce moisture inside then re-sealed it), i dont remember why i didnt use silicon …

I experimented a bit around with 1 and 2 stage TECs on a old heat-sink + fan that was laying around, the best combination interestingly was 2 stages first at 12V 2nd at 5V. though the gain for 2 stages over 1 stage was disappointingly small, IIRC a little over 10°C. Its also interesting to note that my chinese IR thermometer was not able to measure the temperature of the frosted top, it displayed way too low values. Actual real lowest value achieved was measured with a Type K thermocouple, frozen onto the TEC in a drop of water and frosted over for a while (the snowy stuff that forms should provides some extra isolation).
IMG_0377-small
The 2 TECs in above are attached with cable ties, which was very limiting in what could be placed on top

For some reason yesterday i decided to test using the TECs for heating instead of cooling by reversing the input polarity.
That indeed worked and the same device happily boiled drops of water. I didnt think too deep about what the maximum temperature for the TECs was, i didnt expect failure below 180°C, but the top element died at probably around 120-130°C (K type thermocouple in drop of oil on top).
Not entirely believing the apparent facts, i picked another unused separate TEC1-12706 and retried, heating it to 160°C
which seems to have done no harm to it. Though i used the IR thermometer for measuring the 160°C, i should retry this probably with both thermometers but then according to the ebay article page they are max 70°C ;)

Breaking my TEC cooler toy i took it and the failed TEC element apart, Its failure mode was that it showed >10megohm resistance. Cutting its sealant away, it looked like this:
IMG_0460-1280 IMG_0461-1280

And separating it further with a tiny bit of heat and force (probably only heat was needed)
IMG_0463-1280

Also interestingly none of the remaining individual elements tested open, they all had low resistance. I know nothing about TEC failure modes but i wonder if one little part had just cracked from the heat and maybe mechanical stress. They are all in series so one cracking the wrong way should show similar symptoms …

To rebuild the TEC2-toy now ver2, i placed a piece of aluminum on top and tried to attach it with cable ties, but this proofed frustratingly unstable
IMG_0464-1280

My next idea of fixing it with screws, bolts, nuts or such wasnt an option as i lacked parts of sufficient length with non ridiculous diameter. So i cut 2 pieces of the same aluminum stuff and fixed it with 4 springs created out of a single larger spring separated by some foamy stuff for isolation:
IMG_0465-1280 IMG_0468-1280 IMG_0467-1280

In action:
IMG_0470-1280

Also i tested cooling and heating of a glass container with a liquid. (for cooling a drop of water was used as thermal component between glass and aluminum for heating a drop of minnaral oil). Without isolation, the temperature fell to +9.5°C in 1 hour and with some isolation to prevent the warm air from the fan hitting the container, to +2°C in another hour. Iam quite sure sub zero is achievable with a real attempt to prevent coolness loss but i kind of lost patience.
on the hot side i achieved 67°C with the TEC itself being at around 100°C, so if one would risk damaging the unit it might be possible to boil water in a container with it.

Filed under: Electronics,Hardware,Off Topic — Michael @ 5:00
Next Page »

Powered by WordPress