Gadgets

I’ve tested Mapillary on Translapina and I was not impressed

Posted by Strainu on August 14, 2016
Gadgets, Weekend Trips / 2 Comments

Yesterday I decided to give Mapillary a second try (I’ve tested it once before just after launch and it was pretty much unusable). And since I was planning to go over Translapina, I thought: what a great way to see how the app handles various issues one might encounter on mountain road, such as tight curves, changing light and poor GPS cover while discovering a new road (for both me and Mapillary). Southern Romania is pretty well covered in imagery, at least on the main roads, but once you go in the mountains, the coverage drops significantly.

The road in itself was nothing to write home about. I know some of my colleagues are crazy about it, so I’ll probably get some angry looks at work, but the scenery is just not comparable with the Transfăgărășan. There are bends and valleys and mountains in clouds, but the vegetation reminds me more of the desert than the mountain. Plus, as a driver, you always have to look out for rocks and trees falling from the side of the road, as the construction quality is not the best and the earth in the area is very friable as well.

The app was not impressive either. It has come a very long way from the previous version I’ve tested, but it’s still very slow even when it works, which is not always. The app crashed often, especially when the map was on, or simpli freezed for no apparent reason and no warning to the user. I had to pull over, close the app and reopen it. Also, some images are blurred, probably because the app did not wait for the camera to focus. When taking the pics in “distance mode”, no pictures should be taken when the car is stopped. However, the app sometimes failed and continued to take 1 or 2 pictures after the app was completely stopped.

The settings are not uniform (some need to be disabled, but there is no checkbox next to them, instead one simply clicks on them, other need to be enabled) and the different picture modes are insufficiently expained – I had to deduce what each of them does based on many different settings.

Also, a very important problem of the app is that it takes up the screen from nagivation apps. If it is to be used on unknown roads, it should have a “background mode” where it takes pictures while the user is in another app, or, at the very least, allow the map to be configurable in size and position.

Now, I know that some of the issues I mention can be caused by the phone I had, a OnePlus One. It’s not the newest phome you can buy, but if Mappilary developers expect their app to be used only on flagships, they might be in for a nasty surprise.

I will continue to test the Mapillary app for the next few days, but my feeling is it’s not yet ready for prime time.

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No-name chinese battery pack

Posted by Strainu on February 07, 2015
Gadgets / No Comments

Fig. 1: Battery pack

I took advantage of the 11/11 discounts from Aliexpress to get a mobile USB battery pack. I knew the quality will be realtive, so I went for the so-called 20.000mAh model. When it arrived, I decided to make some tests on it. For all tests I used the included USB A-microUSB B cable, which seems capable of providing the advertised 2.1A, but has the data wires disconnected, presumably in order to comply with the Chinese standard for mobile phone chargers.

Fig. 2: Technical specs

What 20,000mAh means is that, in theory, the 3.7V Lithium battery could provide a 1A CC current for 20 hours. This means the battery can hold 3.7V*20Ah=74Wh. However, the USB standard requires 5V CC, so the user will only have 74Wh/5V=14,800mAh available.

Furthermore, the technical details on the back of the battery (Fig. 2) state the capacity is only 48Wh, which means 9,600mAh, or less than half of the advertised capacity for actually loading some devices.

Fig. 3: Input current at the beginning and end

For charging the battery I used a 1A charger, since this is the maximum current accepted by the battery. It took about 12h to load, with the current going down from 750mA to 400mA (Fig. 3). It is only a guesstimate, since I don’t have the exact current curve, but I suspect it can’t have loaded more than 5V*600mA*12h = 36Wh, or 3/4 of the advertised capacity.

The problems started to pile up when trying to use that energy to actually load some devices. I used a Nexus 4 (2100mAh battery) and a OnePlus One (3100mAh) battery. I started charging when the phones had about 20% from the battery left.

It quickly became obvious that I could not leave the phones unsupervised: the battery would get hot really quick (surface temparature above 50°C) and the loading would stop until I restarted the battery. I guess I should be happy that there was a protection circuit, otherwise the loading circuit could become a fire hazard. The problem would become more and more serious as the phones’ batteries charge, so I could not get a definitive loading time for the OPO. All I can say it got from 20% to 83% in 2h10′. This means ~2000mAh in 2.25 hours, or more than a quarter of the presumed capacity of the battery.

With the Nexus 4 things went more smoothly: after leaving the battery to chill for a while, I was capable to load the phone 3 times with one charge of the battery, with some energy left in the battery. This would mean a capacity of at least 80%*2100mAh*3=5040mAh.

Another problem was the serios variation of both voltage and current during loading. It was at least 4 times as large as the one observed with a quality charger (see the movie at the end of the article). I don’t think most modern electronic devices would have any problems with that, but some older devices might encounter issues.

In conclusion, I think we can say I have a battery with a capacity of about 5-6000mAh, which gets really hot pretty fast. It can be a life saver, but it’s not a product one can depend on. I will probably go for a Xiaomi or Anker external battery next – I’ve seen some really good reviews on the Internet about them. For the curious, I have added some additional pictures at the end of the article, with the associated explanations.


Large variations in voltage and current can be observed when loading from the protable battery

Fig. 4: With no load, the Lithium battery voltage of 3.7V is visible.

Fig. 5: Under load, the maximum voltage is about 5.15V.

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Teste pe RDS

Posted by Strainu on December 27, 2014
Gadgets / No Comments
Încărcarea spectrului

Fig1: Încărcarea spectrului de 2,4GHz

Postul ăsta a început ca o discuție pe Facebook; mulțumesc celor care s-au implicat în ea.

Când am cumpărat Raspberry Pi-ul am considerat că are nevoie de o conexiune cu fir, așa că am rămas cu un adaptor wireless “în plus”. Zilele astea am experimentat un pic cu el la laptop, pentru că e mai bun (cel puțin teoretic) decât cel încorporat. E vorba de un EDUP 802.11n “certifcat” (de Teguna) că funcționează cu RPi.

Ulterior, datorită încărcării în banda de 2,4GHz (Fig. 1 este făcută în perioada de Crăciun, în mod normal e și mai aglomerat), am investit și într-un adaptor Edimax 802.11ac, care funcționează și pe frecvența de 5GHz (unde routerul meu e singur deocamdată).

Fig. 2: Speedtest cu EDUP

În primul rând, diferența dintre benzi este vizibilă imediat: lipsa perturbațiilor permite adaptorului să atingă viteza maximă teoretică pe un canal de 80MHz (433Mbps). Din păcate pare destul de greu să configurezi (cel puțin în Linux) sistemul să se conecteze mai întâi (dar nu exclusiv) în banda de 5GHz. Poți să-i spui să folosească doar această bandă, dar asta face imposibilă conectarea la aceeași rețea pe banda de 2,4GHz. Dacă aveți idei despre cum se poate rezolva această problemă, do let me know.

Pe partea de acces Internet, principala observație este că, spre deosebire de 90% din ISP-urile de pe lumea asta, RDS consideră că e mai ok să-mi lase uploadul (mult) mai mare decât downloadul (Fig. 2 și 3) În curând sper să trec la viteza superioară de acces (200Mbps), ceea ce ar trebui să mă apropie și mai mult de line rate, chiar în lipsa unei conexiuni fizice gigabit.

Fig. 3: Speedtest 802.11ac

Diferență dintre noile adaptoare și celelalte adaptoare pe care le-am mai avut e doar la upload: până acum n-am reușit să ating 72Mbps în vreun sens. Cu Dell Wireless 1703 obțineam cam 50Mbps upload, la fel și cu Intelul vechi.

In other news, ruterul Alix făcut “pe genunchi” pare să comute line-rate fără probleme dacă îl scutesc de wireless. Păcat că nu vine și în versiunea gigabit, mi-ar fi plăcut să văd cum se comporta. Restul rețelei e prin switchuri gigabit, deci nu prezintă foarte mult interes din punct de vedere al testării.

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Free WiFi in the metro!

Posted by Strainu on April 14, 2011
Gadgets / 2 Comments

(but just for RDS clients)

A few days ago, I noticed a WiFi access point at Eroilor station. I took out my mobile phone and scanned for wireless networks, and much to my surprise I discovered 2 networks called Digi-Eroilor-1 and Digi-Eroilor-2 (or something like that). When I tried to connect, the first page announced me that the service was only available to RDS landline and Wireless Internet subscribers.

I haven’t got a chance to test the connection, but it’s still a nice touch. I’m guessing it’s kind of a replacement for 3G services, that Vodafone and Orange are providing in the metro, but I haven’t been able to find an official announcement or anything of the kind.

So, has someone else seen these networks, and if yes, where?

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HotSpots Romania

Posted by Strainu on June 30, 2007
Gadgets, My Projects / No Comments

HotSpots Romania is the map of the places that have wireless in Romania. If you now any other hotspot, please leave a comment.

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Programming pays!…

Posted by Strainu on April 23, 2007
Gadgets, School / No Comments

… even in the romanian faculties.

Long time no posts on this blog. Now I’m back with an idea on how to win a black ipod Nano. IXIA has trown one in as a prize for their by-annual challenge. This time you have to make a Linux kernel module that implements the PITIX filesystem. Good luck to all of you!

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Vista

Posted by Strainu on February 04, 2007
Gadgets, Geeks / 3 Comments

So, let’s talk about the new OS. Yes, I know, I’m late again. People have been talking about it for la past 4 days. But I preferred to wait for a legal version from MSDNAA.

OK, let’s take it one by one:

  1. Installation: It takes a little longer than XP, and it’a a lot less clear what the heck it’s doing to my computer. However, one must remember that Vista is almost 4 times larger than XP. So it goes pretty well.
  2. First impression: I had Vista Enterprise Edition and my first impression was: Gee, I must have switched the DVD’s…That’s a black XP! Actually, there are some differences, like the start menu and the welcome panel, but the default settings were lacking AERO (even if my hardware allowed it) and the Sidebar. I had to look in the help center (which, btw, is pretty good) to see how I could activate them.
  3. Security: There is clearly too damn much “security” in that OS. Every time I clicked on something in the Control Panel, the screen went dark and there was a popup asking: Are you sure you want to […]? If you have clicked the button, press Yes. Ofcourse I clicked the god damn button! Stop asking me stupid questions! Installing the flash plug-in for IE became an adventure. It actually took 5 minutes, out of which the actual installation was about 5 seconds 🙂
  4. Looks: Now that’s something that Vista’s good at. AERO has some pretty cool effects (even if I had to dig for them in the help files) and the Sidebar can be pretty useful once you get used to it. The new IE7-like looks for Windows Explorer is also interesting and easy to learn.
  5. Hardware: Not so good 🙁 Vista wasn’t capabable to see my embedded sound card and the XP driver did not work. So I’m stuck in silence :D, because my MB is too old to hope for a Vista driver. The other harware seemed to be OK, even if I haven’t tried all of the USB gadgets. Another bad point was the fact that Vista alone was eating up 75% of my 512MB memory. I can only dream of actually starting Visual Studio on Vista and still being able to do something on it.
  6. Crashes: It’s a Windows, I know, but come on… 2 Explorer crashes in half an hour? XP SP2 had given me hope for more.

So, am I gonna keep it? No, because I can’t do anything useful with it (because of the lack of memory), I don’t like all the security warnings and my XP hasn’t crashed in a very, very, very long time 🙂 Why change something that’s working?

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Blogs roundup

Posted by Strainu on December 07, 2006
Gadgets, Geeks, School / 1 Comment

Well, since Andressa seems to have a good time in Poland and she doesn’t bother with the blog any more, we all have to find alternate sources of fun 🙂 Here are my nominations:

  • Entering the IT industry from Tudor Damian – some common sense pieces of advice for the future IT professionals
  • Bash tricks: comparing floating point numbers by Petre – an somewhat old post about BASH. Interesting because that’s one of the problems in my homework for the Operating Systems course 🙂
  • Yahoo! fights messenger spam by evolve – fact or just messenger trouble? We’ll see…
  • Metro etiquette by Just me – an excellent idea! There is a good reason for the yellow footsteps on the Bucharest metro’s escalators. Ever wondered what’s that reason?
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IE7 final

Posted by Strainu on October 21, 2006
Gadgets / 1 Comment

A while ago I was telling you about IE7RC1. I now have the final version, and unfortunately most of the problems are still there. I still need to boot in Safe Mode to be able to install it (this seems to be a Windows problem actually) and I still can’t put the homepages as I wish – but this time, it only puts msn.com as the first entry, but leaves the others untouched.

The good news: the new tab mini-tab looks better. 😀 And I’ve managed to set the toolbar buttons in an acceptable layout. The pop-up blocker and phishing blocker are quite useful.

Overall, I can say that the differences between IE and Firefox are now a matter of layout more than anything else. But for me, Firefox is still better: at least I can put the start pages that I like. So, Tudy, what do YOU think?

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Blogvertising

Posted by Strainu on September 24, 2006
Cool webpages, Gadgets, My Projects / 2 Comments

The publicty on blogs idea seems to have a name now: blogvertising. There are now 50 blogs on the list and growing.

To have an indea of how big (or small) this thing will get, I made a simple program to follow the trafic.ro stats of the registered sites. Only about a third of all sites have the trafic.ro tracker, but it still gives a pretty good idea of how many users are we talking about.

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