etbe - Russell Coker

Voltage Inside a Car

I previously wrote a post with some calculations about the power supplied to laptops from a car battery [1]. A comment on the post suggested that I might have made a mistake in testing the Voltage because leaving the door open (and thus the internal lights on) will cause a Voltage drop.

So I’ve done some more tests:

Test	Voltage
battery terminals	12.69
front power socket with doors closed	12.64
front power socket with doors open OR ignition switch on	12.37
cigarette lighter socket with ignition switch on	12.32
front power socket with doors closed and headlights on	11.96
front power socket with engine running	14.38
front power socket with engine running and headlights on	14.29

In my previous tests I recorded 12.85V inside my car (from the front power socket which although having the same connector as a cigarette lighter isn’t designed for lighting cigarettes) and 13.02V from the battery terminals – a 0.17V difference. In my tests today I was unable to reproduce that but I think that my biggest mistake was to take the reading too quickly. Today I noticed that it took up to a minute for the Voltage to stabilise after opening a door (the Voltage dips after any current draw and takes time to recover) so a quick reading isn’t going to be accurate.

My car is a Kia Carnival which has two sockets in the front for power and for actually lighting cigarettes. The one for lighting cigarettes has a slightly lower Voltage and only works when the ignition is turned on. The car also has a power socket in the boot (the trunk for US readers) which delivers the same Voltage as the power socket in the front.

Also one thing to note is that today is a reasonably cold day (16.5C outside right now) and my car hasn’t been driven since last night so the battery would be quite cold (maybe 12C or less). My previous measurements were taken in summer so the battery would have been a lot warmer and therefore working more effectively.

Conclusion

The Voltage drop from turning on the internal lights surprised me, I had expected that a car battery which is designed to supply high current wouldn’t be affected by such things. Certainly not to give a 2% Voltage drop! The Voltage difference from reading inside the car and at the battery terminals might be partly due to the apparent lead coating on the terminals, I pushed the probes of my multimeter beneath the surface of the metal and got a really good connection.

The 14% Voltage increase when the engine was running was also a surprise. It seems to me that if you are running a power hungry device (such as a laptop) it would be a good idea to disconnect it when the engine is turned off. A 14% higher voltage will give a 14% lower current if the PSU is efficient and therefore less problems with heat in the wiring and less risk of blowing a fuse.

Also it’s a good idea to be more methodical about performing tests than I was before my last post. There are lots of other tests I could run (such as testing after the engine has been running for a while) but at the moment I don’t have enough interest in this topic to do more tests. Please leave a comment if there’s something interesting that you think I missed.

[1] http://etbe.coker.com.au/2013/01/24/power-supplies-wires/

Effective Conference Calls

I’ve been part of many conference calls for work and found them seriously lacking. Firstly there’s a lack of control over the call, so when someone does something stupid like putting an unmuted phone handset near a noise source there’s no way to discover who did it and disconnect them.

Another problem is that of noise on the line when some people don’t mute their phones, which is related to the lack of control as it’s impossible to determine who isn’t muting their phone.

Possibly the biggest problem is how to determine who gets to speak next. When group discussions take place in person non-verbal methods are used to determine who gets to speak next. With a regular phone call (two people) something like the CSMACD algorithm for network packets works well. But when there are 8+ people involved it becomes time consuming to resolve issues of who speaks next even when there are no debates. This is more difficult for multinational calls which can have a signal round trip time of 700ms or more.

I think that we need a VOIP based conference call system for smart phones to manage this. I think that an ideal system would be based on the push to talk concept with software control that only allows one phone to transmit at a time. If someone else is speaking and you want to say something then you would push a button to indicate your desire but your microphone wouldn’t go live while the other person was speaking. The person speaking would be notified of your request and one of the following things would happen:

You are added to the queue of people wishing to speak. When the other person finished speaking the next person in the queue gets a turn.
You are added to the queue and the moderator of the call chooses who gets to speak next. This isn’t what I’d prefer but would probably be desired by managers for corporate calls.
You get to interrupt the person who’s speaking. This may not be ideal but is similar to what currently happens.

Did I miss any obvious ways for the system to react to a talk request?

Is there any free software to do something like this? A quick search of the Google Play store didn’t find anything that seems to match.

Geographic Sorting – Lessons to Learn from Ingress

I’ve recently been spending a bit of my spare time playing Ingress (see the Wikipedia page if you haven’t heard of it). A quick summary is that Ingress is an Android phone game that involves geo-location of “portals” that you aim to control and most operations on a portal can only be performed when you are within 40 meters – so you do a lot of travelling to get to portals at various locations. One reasonably common operation that can be performed remotely is recharging a portal by using it’s key, after playing for a while you end up with a collection of keys which can be difficult to manage.

Until recently the set of portal keys was ordered alphabetically. This isn’t particularly useful given the fact that portal names are made up by random people who photograph things that they consider to be landmarks. If people tried to use a consistent geographic naming system (which was short enough to fit in large print on a phone display) then it would be really difficult to make it usable. But as joke names are accepted there’s just no benefit in having a sort by name.

A recent update to the Ingress client (the program which runs on the Android phone and is used for all game operations) changed the sort order to be by distance. This makes it really easy to see the portals which are near you (which is really useful) but also means that the order changes whenever you move – which isn’t such a good idea for use on a mobile phone. It’s quite common for Ingress players to recharge portals while on public transport. But with the new Ingress client the list order will change as you move so anyone who does recharging on a train will find the order of the list changing during the process and it’s really difficult to find items in a list which is in a different order each time you look at it.

This problem of ordering by location has a much greater scope than Ingress. One example is collections of GPS tagged photographs, it wouldn’t make any sense to mix the pictures of two different sets of holiday pictures because they were both taken in countries that are the same distance from my current location (as the current Ingress algorithm would do).

It seems to me that the best way of sorting geo-tagged items (Ingress portals, photos, etc) is to base it on the distance from a fixed point which the user can select. It could default to the user’s current location but in that case the order of the list should remain unchanged at least until the user returns to the main menu and I think it would be ideal for the order to remain unchanged until the user requests it.

I think that most Ingress players would agree with me that fixing annoying mis-features of the Ingress client such as this one would be better for the game than adding new features. While most computer games have some degree of make-work (in almost every case a computer could do things better than a person) I don’t think that finding things in a changing list should be part of the make-work.

Also it would be nice if Google released some code for doing this properly to reduce the incidence of other developers implementing the same mistakes as the Ingress developers in this regard.

Links March 2013

Russ Allbery wrote an informative post about how to determine which charities are worth donating to [1]. He has a link to another article about the charities to which he donates and concentrates on ways of analysing the effectiveness of charities. So someone who has different ideas about which types of charity are worthy of donation could still learn a lot from his post.

Adam Green wrote an interesting article for The New Yorker about Apollo Robbins who is one of the world’s best pick-pockets [2]. Apollo picks pockets as a magician to entertain people and always returns what he steals. Now he is working with neuroscientists who are devising experiments to determine why his tricks work.

Rick Falkvinge wrote an insightful article describing the way that the copyright monopoly is in direct opposition to the freedom to make contracts [3]. It’s a good rebuttal of a common argument in favor of copyright law.

Seth Godin gave an interesting TED talk about the problems with the education system, how and why it teaches conformity and little else [4]. One of his suggestions for improvement is to have students spend their evenings watching lectures by experts and class time asking questions. He also says that everything should be open book and that there is no value in memorising anything – it’s a bit of an overstatement but it’s essentially correct.

Cory Doctorow wrote an interesting article for The Guardian about positive externalities and copyright law [5]. I think that he didn’t choose the best way of framing this issue, but he makes some very interesting points anyway.

Andrew Norton wrote an interesting article about how to reduce corruption in the police force and other government agencies [6]. A large part of this is based on making them subject to the same laws as everyone else, which seems to be a radical idea.

Valerie Aurora wrote an insightful blog post about suicide [7].

Emily Oster gave an interesting TED talk about the factors that determine the spread of AIDS in Africa [8]. It’s quite different to what you probably expect.

Kogan Mobile

Kogan Mobile is the newest virtual telco in Australia [1]. They resell Telstra 3G (not NextG or LTE) and while their coverage isn’t as good as the full Telstra service it’s more than adequate for my needs as they provide 3G coverage to 97% of the population and 2G+3G coverage to 98.5%. Their coverage is probably a lot better than Three who had the worst record of network coverage in Australia yet managed to always provide coverage where I wanted it – I was a happy Three customer for more than 6 years.

Kogan’s main selling point is that they offer unlimited calls to Australian mobile phones and land-lines and unlimited SMS for a pre-paid fee of only $300 per annum ($25 per month on average). My parents have been getting unpleasantly large phone bills which have considerably more than $25 of calls to mobile phones every month so an obvious solution for them is to sign up for a Kogan mobile phone and use it for all such calls. There are other ways my parents could save money on calls (such as VOIP) but a mobile phone is easiest and offers other benefits such as running Android apps (when compared to using a non-smart phone).

6G of Data!

Kogan also offers 6G of data per month, the down-side to this is that they bill in 1MB increments per “session”. I was worried that this might be per TCP connection or something else silly but I decided to sign my parents up for it as they aren’t going to use a lot of data (they claim that they don’t want to use the Internet on their phone but I know better). I’ve done some tests on the SIM I got for my parents. For testing purposes I installed the Kogan SIM in my wife’s new Nexus 4 and had it provide Wifi net access to my phone while we were playing Ingress.

So far after 2 days which involved a reasonable amount of Ingress (I reached level 7) as well as all the usual stuff that happens in the background for two phones (checking email, news, weather, etc) Kogan considers that 177MB have been used out of the 6144MB for the month, which means that even with what is an unusual amount of traffic for us the account in question still isn’t going to use half the quota for the month. Now that 10 days have elapsed with less intense usage Kogan considers that a total of 1373MB have been used.

days	received	sent	Kogan
2	127.24	41.54	177
10	959.39	299.6	1373

Kogan also don’t seem to mention whether they bill for transmitted data. I used the 3G Watchdog app to measure the amount data transferred, the above table has the amounts of data that 3G Watchdog considers were sent and received along with the amount that is listed by the Kogan Android app. My past experience with 3G Watchdog and Virgin Mobile is that it’s usually quite accurate but has been over-reporting the data transfers recently (I think that Virgin is only billing me for downloads while 3G Watchdog counts uploads). So the relatively small difference between the 3G Watchdog report and what Kogan thinks I’ve done means that either rounding the “session” up to the nearest meg doesn’t make any significant difference (which would imply that a “session” can be a long time) or that Kogan isn’t counting uploaded data and the session rounding up only adds about 40% to the total recorded transfer.

My current plan with Virgin Mobile gives me 1.5G per month of quota, so as long as Kogan’s rounding doesn’t increase the recorded data transfer by a factor of 4 I will still be able to transfer more data with Kogan while paying less. One disadvantage of using Kogan is that I might have to tweak programs like my email program to poll less frequently to avoid excessive session charges (a program polling every 5 minutes would use up the 6G quota in 21 days if each poll counted as a session) – although current tests indicate that this won’t be necessary. But the up-side is that there are no extra fees with Kogan, they merely restrict data access – for my use and that of most people I know it’s better to have data access cut off than to receive a large bill.

The Kogan Android App

Kogan has an Android app that will give the status of your account and allow you to change the plan etc. This is quite nice but one major disadvantage is that it’s also a sales app for the Kogan online store. This is bad for the user as some aspects of what I consider the core functionality are limited (for example there’s no way to force a poll of the data usage count or determine how current the data is). But there’s an obvious advantage to Kogan in providing a way to sell their goods that is going to be used by every customer of Kogan Mobile.

The sales part of the app isn’t very functional IMHO, it doesn’t seem to have basic functionality such as sorting a list of items by price.

Benefits of Kogan

6G of data is a lot!

$300 per annum is quite cheap, anyone who makes any serious use of phones will be paying more than that in Australia.

Lack of extra fees means that there is little need to restrict net access. I can risk getting cut off near the end of the month but I can’t risk the potential for hundreds of dollars in excess fees.

The Kogan app shows me the data used so I will probably uninstall 3G Watchdog, having one less program running is a good thing.

You get a free SIM (value $5) when you buy a phone from Kogan.

Disadvantages of Kogan

They are new to the Telco business and admit that their customer service is lacking due to unexpected demand.

If you order a SIM now they state that it will arrive in April. Apparently they are deliberately delaying orders because they can’t cope with demand.

The included call quota doesn’t include international calls. While unlimited free calls in Australia is great if you make many international calls then this could end up costing you more. Other mobile telcos such as Lebara offer good deals for International calls, it could be an option to use a Lebara SIM with an old non-smart phone while using Kogan for your smart phone.

I am concerned about the lack of detail about how data is accounted. If the definition of a “session” changes then 6G could turn out not to be enough. As Kogan is reselling a Telstra service it is possible that Telstra could change the deal without Kogan being able to stop them.

Conclusion

I will move my phone and my wife’s phone to Kogan ASAP. My general idea is to sign us up for Kogan about 2 weeks apart, so if one phone runs out of the 6G data quota then the other phone can be used as a Wifi access point for 2 weeks. If the phones don’t both have their quota end at the same time then there is less chance of both phones running out during a high traffic month.

[1] https://www.koganmobile.com.au/

Serious Begging

This evening I was driving through one of the inner suburbs of Melbourne when a man flagged me down. He said that his mother was dying and he needed a taxi ride to some hospital far away and needed to borrow $200. He was saying something about his phone, I wasn’t sure if he was planning to give me his phone number so I could call him to ask for repayment or offering his phone as collateral on the loan (incidentally a well known scam is to offer a stolen phone as collateral for a loan, it’s a way of selling a locked phone that doesn’t have cables).

I’ve encountered many beggars over the years, but he was by far the most serious about it – he demonstrated the level of desperation that I’ve only previously seen documented in history books and reports from travelers who visited developing countries. I will never know if his mother was dying, there are lots of other reasons why someone might urgently need cash (most of which won’t get much sympathy).

I gave him $20 as a gift. If his story was legitimate then I gave him 10% of what he needed so he only had to find another 9 people willing to do the same. If he was lying then I can afford to lose $20. In any case I definitely wasn’t going to do what he asked and withdraw hundreds of dollars from an ATM for him. Also regardless of whether he was telling the truth I didn’t want to have him repay me, if he’s telling the truth then I’m happy to give money to him and if he’s not then I’m better off avoiding him in future. If I had $50 I would probably have given it to him, but $200 is too much.

As I drove off I looked in my rear-vision mirror and saw him running between cars on the road trying to flag someone else down. Running through moving traffic on a Saturday night is another indication of how serious he was, generally someone who’s in a good state of mind and wants a long and healthy life won’t do that.

iPhone vs Android

A friend who’s a long-time iPhone user just asked for my advice about whether to get a Samsung Galaxy S3, a Samsung Galaxy Note 2, or a iPhone 5.

Advantages for Android

I think that liberty should be the first consideration, I’ve previously written about how Android phones won’t necessarily give you as much freedom as you desire if you buy on the basis of price and features [1]. But even the least free Android options are way better than the iOS (iPhone and iPad) environment. This isn’t necessarily a big deal for my friend, like most of the population he usually just wants things to work – being able to hack them isn’t such an issue. However unlike most of the population he does make a reasonable portion of his income from software development and it could be that he will have a contract for developing an app on a mobile device – in which case the freedom to tinker on Android will help him. He could use an iPhone for his personal use and develop on an Android platform for his clients, but generally it’s more efficient if your personal use of technology is similar to that of your clients. The Nexus devices are very good for liberty and they also have nice hardware at a low price, I’ve just got a Nexus 4 for my wife and it’s very nice.

The next issue is that of hardware standards, I’ve previously written about the potential for developing a standard form factor for Android phones [2] although this doesn’t seem likely to be implemented in the near future. The wide range of Android hardware means that the range of cases etc on the market is rather small. But the advantage of the wide range is that with an Android phone you can have a device that’s bigger, smaller, cheaper, cuter, or faster than an iPhone. There are Android devices which have a higher resolution, more RAM, more storage (if you include SD storage), or has other benefits over an iPhone. For whatever reasonable range of specs appeal to you you can probably find a device to match. I’ve previously written about the way the ideal size for devices depends on your hand size and your preferred manner of gripping the device [3], so the lack of size range in Apple devices is not just a limitation on personal choice but also a failure to properly support people with different size hands. Depending on the preferred manner of gripping a phone the iPhone 5 is either too big for an average woman or too small for a tall man.

The Google Play store apparently has more applications than the iPhone/iPad App Market. This difference can be expected to increase now that the Samsung Galaxy S3 is outselling the iPhone 5. Comparing the number of unit sales of the iPhone vs Android phones is no longer interesting, comparing Samsung to Apple is the interesting thing.

Advantages for the iPhone

By all accounts it’s quite an easy process to backup and restore all iPhone settings. You can expect that after losing an iPhone you can just connect the new one to your PC and have it work in exactly the same way after all the data is transferred. Trying to do such things on Android is merely difficult if you have root access to your phone and the source and destination phones are of exactly the same make and model. But if you have different versions of the phone or if you don’t have root access then it may be impossible. I welcome comments from anyone who knows of good solutions to this problem.

The iPhone achieved a reasonable share of the smart-phone market before Android really started going well so there are a lot of people who are used to the iPhone. Simply by being unfamiliar Android will be a more difficult option for people who have used the iPhone – such as my friend. But it is possible to learn other systems. Generally I think that this may be a big issue for people who use Macs for all their other computing. But if the only Apple product you use is an iPhone then switching to Android shouldn’t be a big deal.

Update:

One feature of the iPhone that is very important to my friend is the ability to add arbitrary tags in the contacts. In addition to name, address, phone number, etc he wants to add arbitrary notes related to his business. While he could put that sort of thing into the “Notes” field in Android he would rather have several fields with his own names. Android 4.1.x definitely doesn’t have this and I can’t test Android 4.2.x at this time. Is there any way of doing such things on Android?

Conclusion

It seems to me that Android devices are better in every way apart from backup, restore, and general management. If I was about to buy 100 phones then I’d probably consider the iPhone (not necessarily buy but definitely consider). But for a single user I definitely recommend Android devices.

The Android devices which seem good at the moment are the Galaxy S3 (which I’m using now), the Nexus 4 (which is really good apart from being unable to change the battery or add more storage), and the Galaxy Note 2 (which is about the biggest phone available).

One of the things that my friend wants to do is to use a phone instead of a tablet or laptop. I think that the Galaxy Note 2 is the only option for him.

Conversion of Video Files

To convert video files between formats I use Makefiles, this means I can run “make -j2” on my dual-core server to get both cores going at once. avconv uses 8 threads for it’s computation and I’ve seen it take up to 190% CPU time for brief periods of time, but overall it seems to average a lot less, if nothing else then running two copies at once allows one to calculate while the other is waiting for disk IO.

Here is a basic Makefile to generate a subdirectory full of mp4 files from a directory full of flv files. I used to use this to convert my Youtube music archive for my Android devices until I installed MX Player which can play every type of video file you can imagine [1]. I’ll probably encounter some situation where this script becomes necessary again so I keep it around. It’s also a very simple example of how to run a batch conversion of video files.

MP4S:=$(shell for n in *.flv ; do echo $$n | sed -e s/^/mp4\\// -e s/flv$$/mp4/ ; done)

all: $(MP4S)

mp4/%.mp4: %.flv
avconv -i $< -strict experimental -b $$(~/bin/video-encoding-rate $<) $@ > /dev/null

Here is a more complex Makefile. I use it on my directory of big videos (more than 1280*720 resolution) and scales them down for my favorite Android devices (Samsung Galaxy S3, Samsung Galaxy S, and Sony Ericsson Xperia X10). My Galaxy S3 can’t play a FullHD version of Gangnam Style without going slow so I need to do this even for the fastest phones. This makefile generates three subdirectories of mp4 files for the three devices.

S3MP4S:=$(shell for n in *.mp4 ; do echo $$n | sed -e s/^/s3\\// -e s/.mp4$$/-s3.mp4/ -e s/.flv$$/-s3.mp4/; done)
XPERIAMP4S:=$(shell for n in *.mp4 ; do echo $$n | sed -e s/^/xperiax10\\// -e s/.mp4$$/-xperiax10.mp4/ -e s/.flv$$/-xperiax10.mp4/; done)
SMP4S:=$(shell for n in *.mp4 ; do echo $$n | sed -e s/^/galaxys\\// -e s/.mp4$$/-galaxys.mp4/ -e s/.flv$$/-galaxys.mp4/; done)

all: $(S3MP4S) $(XPERIAMP4S) $(SMP4S)

s3/%-s3.mp4: %.mp4
avconv -i $< -strict experimental -s $(shell ~/bin/video-scale-resolution 1280 720 $<) $@ > /dev/null

galaxys/%-galaxys.mp4: %.mp4
echo avconv -i $< -strict experimental -s $(shell ~/bin/video-scale-resolution 800 480 $<) $@ > /dev/null

xperiax10/%-xperiax10.mp4: %.mp4
echo avconv -i $< -strict experimental -s $(shell ~/bin/video-scale-resolution 854 480 $<) $@ > /dev/null

The following script is used by the above Makefile to determine the resolution to use. Some Youtube videos have unusual combinations of width and height (Linkin Park seems to like doing this) so I scale them down so it fits the phone in one dimension and the other dimension is scaled appropriately. This requires a script from the Mplayer package and expects it to be in the location that it’s used in the Debian package, for distributions other than Debian a minor change will be required.

#!/bin/bash
set -e
OUT_VIDEO_WIDTH=$1
OUT_VIDEO_HEIGHT=$2

eval $(/usr/share/mplayer/midentify.sh $3)
XMULT=$(echo $ID_VIDEO_WIDTH*100/$OUT_VIDEO_WIDTH | bc)
YMULT=$(echo $ID_VIDEO_HEIGHT*100/$OUT_VIDEO_HEIGHT | bc)
if [ $XMULT -gt $YMULT ]; then
NEWX=$OUT_VIDEO_WIDTH
NEWY=$(echo $OUT_VIDEO_WIDTH*$ID_VIDEO_HEIGHT/$ID_VIDEO_WIDTH/2*2|bc)
else
NEWX=$(echo $OUT_VIDEO_HEIGHT*$ID_VIDEO_WIDTH/$ID_VIDEO_HEIGHT/2*2|bc)
NEWY=$OUT_VIDEO_HEIGHT
fi
echo ${NEWX}x${NEWY}

Note that I can’t preserve TAB characters in a blog post. So those Makefiles won’t work until you replace strings of 8 spaces with a TAB character.

[1] https://play.google.com/store/apps/details?id=com.mxtech.videoplayer.ad

Phone/Tablet Sizes

The above two pictures show me holding a Samsung Galaxy S3 which has a 4.8″ display in my left hand and a Sony Ericsson Xperia X10 which has a 4.0″ display in my right hand. I am holding both phones in a manner that allows me to touch the top opposite corner with my thumb – the position I need for one-handed phone use. The Xperia X10 can be completely enclosed by my hand, when I have a bottom corner resting in my palm it won’t slide down while the Galaxy S3 can slide.

Also one thing I didn’t realise before having the pictures taken is that my posture is quite different when using the two phones. With the Galaxy S3 my wrist is clearly bent and this seems more likely to cause me to have more problems with Carpal Tunnel Syndrome [1]. I haven’t had any serious problems with CTS for the last 2.5 years but I have had minor problems that suggest that I will have to be careful about my posture for the rest of my life.

So it seems that a 4.8″ phone is just too big for ideal one-handed use (grasping the vertical phone from the bottom). As I had CTS problems with my left hand I will try to use my new phone with my right hand as much as possible. Also I can reach further than the width of the phone screen when I grasp it from the side, so for me a size of about 5.2″ would be better than the 4.8″ of the Galaxy S3. It’s quite likely that the Samsung Galaxy Note with it’s 5.3″ screen would be a better device for me to grasp from the side. But the Galaxy Note 2 might be a little too large for me.

Note that I am only considering ways of holding the device that permit full operation. Anything that involves changing position for different uses or occasionally using two hands for a mostly one-hand operation doesn’t count.

The above picture is of me holding a 7″ Android tablet (which I have just returned to Aldi [2]). When holding it from the sides I can reach more than half the screen with one hand so it seems that the ideal size for a tablet to be held in two hands for me would be 8″ or even a little larger. A tablet larger than that could only be properly used if resting on my lap or a desk – so for me 8″ is the size that differentiates things which can be strictly used as tablets (holding with two hands and using thumbs for input) and things which are more like Netbooks (on desk typing).

Ideal Device Sizes for people based on Height

I am about 190cm tall. If we assume that height and hand size are strongly correlated then we can look at median heights of various age groups and determine what might be a good device size. I am also assuming that everyone wants to have the largest possible device, but some people have other criteria such as the size of their pockets.

For me it’s 8″ tablet, 5.2″ side-grip phone, and 4″ bottom-grip phone. I used data from a chart of the average heights of American boys [3] and a chart of the average heights of American girls [4] to determine what size devices might suit children of various ages. Note that before the age of 12 the height of boys and girls is near enough to identical.

Device	Two Hand Tablet Use	Phone Grasp from Side	Phone Grasp from Below
7″ tablet	14yo boy or 17yo girl	noone	noone
Galaxy Note 5.3″	10yo	95th percentile 17yo boy	noone
Galaxy S3 4.8″	6yo	17yo boy or 95th percentile 17yo girl	almost noone
Galaxy S and iPhone 5 4.0″	3yo	10yo	95th percentile 17yo boy
iPhone 4 3.5″	noone	8yo	14yo boy or 16yo girl

One thing that particularly interests me is the educational use of Android devices for children. As few people buy new phones and tablets for young children that largely means that children borrow devices from their parents or are given older phones when relatives no longer need them. So it seems that if all other things are equal then an adult might choose a phone with a 4.8″ display to allow it to be used as a tablet by children in the 6-10 age range.

Conclusion

It seems that the iPhone 4 is a good size for one-handed use by women of average height. By the standards of the people who don’t regard gripping a phone from below as a significant feature the iPhone 4 would be designed for the hand of an 8yo. By any standards all iPhones other than the iPhone 5 were not the ideal size for most adults to use – maybe they are well designed to fit in a pocket while unused. Charles Stross criticised the iPhone because it’s too small to be seen well by people with poor vision [5], he also makes many other interesting points about the use of phones and I recommend reading his article (and the rest of his blog).

The common tablet size of 7″ seems like it might be ideal for women to hold with both hands, but for men of average height a 7.5″ tablet might be better suited, it sounds like a small difference but it changes button size (good for people with thicker fingers) and allows displaying more data at once (15% greater screen area). Of course if you want to use a tablet on a desk then something much bigger would be better, maybe 12″ or 14″. I think that there is a real market for 14″ tablets that are designed to be carried around the home or office and then used on a table or lap which differs from the tablets that are designed to be more portable.

There is also the use case of holding the phone in one hand while typing with the other which I haven’t considered in this post. I don’t think it’s interesting because in that case almost everyone will find that the limitation is the size of their pockets and the size of an object that can be held to one’s face for a phone call not the size of their hands. I’ve previously written about my search for Geeky jeans and the ability to put a 7″ tablet in my jeans pocket [6]. So I think that pocket size isn’t a phone selection issue for men. The fact that women’s clothing tends to have tiny pockets is another issue, if someone knows of a good analysis of phone size vs pockets in women’s clothes then please let me know.

Links February 2013

Aaron on Software wrote an interesting series of blog posts about psychology and personal development collectively Titled “Raw Nerve”, here’s a link to part 2 [1]. The best sections IMHO are 2, 3, and 7.

The Atlantic has an insightful article by Thomas E. Ricks about the failures in leadership in the US military that made the problems in Afghanistan and Iraq a lot worse than they needed to be [2]

Kent Larson gave an interesting TED talk about how to fit more people in cities [3]. He covers issues of power use, transport, space use, and sharing. I particularly liked the apartments that transform and the design for autonomous vehicles that make eye contact with pedestrians.

Andrew McAfee gave an interesting TED talk titled “Are Droids Taking Our Jobs” [4]. I don’t think he adequately supported his conclusion that computers and robots are making things better for everyone (he also presented evidence that things are getting worse for many people), but it was an interesting talk anyway.

I Psychopath is an interesting documentary about Sam Vaknin who is the world’s most famous narcissist [5]. The entire documentary is available from Youtube and it’s really worth watching.

The movie Toy Story has been recreated in live action by a couple of teenagers [6]. That’s a huge amount of work.

Rory Stewart gave an interesting TED talk about how to rebuild democracy [7]. I think that his arguments against using the consequences to argue for democracy and freedom (he suggests not using the “torture doesn’t work” and “women’s equality doubles the workforce” arguments) are weak, but he made interesting points all through his talk.

Ernesto Sirolli gave an interesting TED talk about aid work and development work which had a theme of “Want to help someone? Shut up and listen!” [8]. That made me think of Mary Gardiner’s much quoted line from the comments section of her Wikimania talk which was also “shut up and listen”.

Waterloo Labs has some really good engineering Youtube videos [9]. The real life Mario Kart game has just gone viral but there are lots of other good things like the iPhone controlled car and eye controlled Mario Brothers.

Robin Chase of Zipcar gave an interesting TED talk about various car sharing systems (Zipcar among others), congestion taxes, the environmental damage that’s caused by cars, mesh networks, and other things [10]. She has a vision of a future where most cars are shared and act as nodes in a giant mesh network.

Madeleine Albright gave an interesting TED talk about being a female diplomat [11]. She’s an amazing speaker.

Ron Englash gave an interesting TED talk about the traditional African use of fractals [12]. Among the many interesting anecdotes concerning his research in Africa he was initiated as a priest after explaining Georg Cantor’s set theories.

Racialicious has an insightful article about the low expectations that members of marginalised groups have of members of the privileged groups [13].

Rick Falkvinge has a radical proposal for reforming copyrights with a declared value system [14]. I don’t think that this will ever get legislative support, but if it did I think it would work well for books and songs. I think that some thought should be given to how this would work for Blogs and other sources of periodical content. Obviously filing for every blog post would be an unreasonable burden. Maybe aggregating a year of posts into one copyright assignment block would work.

Scott Fraser gave an interesting TED talk about the problem with eyewitness testimony [15]. He gave a real-world example of what had to be done to get an innocent man acquitted, it’s quite amazing.

Sarah Kendzior wrote an interesting article for al Jazeera about the common practice in American universities to pay Adjunct Professors wages that are below the poverty line [16]. That’s just crazy, when students pay record tuition fees there’s more than enough money to pay academics decent wages, where does all the money go to anyway?

etbe – Russell Coker

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Links February 2013

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