How to fix a broken screen on a Nexus 4

Posted in Gadgets, Howto, Tech on June 24th, 2014 by Andy
Broken glass

Not really what you want to see…

A couple of weeks ago I dropped my Nexus 4 and cracked the screen. The touchscreen was still working ok, but I went ahead and replaced the screen anyway. Here’s how…

On the Nexus 4 the screen is bonded to the touchscreen digitiser behind it, so unless you want some major hassle it’s easiest to just replace the screen and digitiser as one unit. You can pick up kits on Ebay to do this, mine cost about £45 and included screen, digitiser, tools and the frame (which was nice, as my screen frame was getting a bit worn).

I followed this video. The only things I would point out are that it’s easier to remove the SIM card holder first. Doing this makes it easier to pry the back shell off. If you’re replacing the whole screen unit you also don’t need to worry about heat the screen and seperating the components. Don’t forget to transfer over all the fiddly bits like volume buttons and the headphone jack from the old frame to the new one.

It’s not at all hard to do, with the right tools it’s just a matter of working carefully and methodically. My phone is good as new.

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Should I buy refurbished appliances and gadgets?

Posted in Gadgets, Tech on May 19th, 2014 by Andy

Yes you should, and the reason why has more to do with bathtubs than you might have expected. Not only are refurbished goods a lot cheaper than brand new ones, they’re actually better. Meet the Bathtub Curve:

The Bathtub Curve

Those of us who are paid to dip our toes into reliability engineering will be familiar with this graph:

The curve shows decreasing probability of failure over the short term

Engineers developed the bathtub curve from analysing the failure rates of huge numbers of machines. Basically it shows that things are highly likely to fail early in service (due to manufacturing defects, etc), then settle in and run reasonably reliably until they start to wear out and fall apart. Now, in real life nothing fits the nice smooth curve exactly, but in general it holds true. That’s why everything you buy comes with a warranty, manufacturers expect a certain percentage of their stuff to die straight away.

The bathtub curve, showing the lower chance of failure after the initial period

After a short period of use the chance of failure drops substantially

Now, when stuff  develops a fault in early service, people send it back to the manufacturer who often sends out a replacement. All good so far. The manufacturer repairs the original device and sells it on as a refurb for a substantial knockdown. My whole point is: having been in service for a short time and having already surfaced any problems, the refurbed machine is now less likely to conk out than a new machine. You’re now getting a machine that will be more reliable and costs less, and you’ve still got a warranty if it does go wrong again. Why buy anything brand new if you could get a better one for less? The worst wear and tear I’ve seen on any refurbed tech or appliances are some minor cosmetic scratches, which you’ll have on your new gizmo within a few weeks anyway.

I’m interested, hook me up.

Plenty of big companies have a refurb scheme. If you’re in the UK check out:


PC World

eBay (don’t be afraid of this one, lots of people run small businesses through eBay where they sell on the refurbed units from bigger suppliers)

Amazon refurbished

John Lewis Swindon outlet

Marks and Spencer outlet

Currys household applicances

Currys computing

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How to replace your Sky fibre router

Posted in Computers, Howto, Tech on May 4th, 2014 by Andy
A person having handcuffs put on them

Not keen on paying Sky to do this to your connection?

Whatever your reasons are for wanting to replace your Sky fibre router (and there are a few) the common denominator is that Sky don’t make it easy. These instructions will allow you to connect to your Sky fibre connection using your own router. The model I’m demonstrating is the Asus RT-N66U.

The legal bit

  • You can read Sky Fibre Broadband’s T&Cs here.
  • Your old Sky fibre router is your property, but the software on it belongs to Sky. You’re not allowed to flash the firmware, and selling it could be dubious. Best hang on to it for as long as you’re a customer.
  • If you need to speak to Sky customer services the easiest thing to do would be plug your Sky router back in and pretend to be just like the rest of their customers. They’ll only support the hardware they’ve supplied.

I’m keen! But how?

  1. Obtain your Sky username and password by doing a little sniffing around your router.
  2. Unplug your Sky router and hide it in the back of a dark cupboard.
  3. Get a new router and flash the firmware on it to a Sky-compatible version.
  4. Put your Sky username into the new router and connect.
  5. Win!

Getting your Sky username and password

As you’re no doubt aware, you’re not told what the Sky username and password you use to connect to their network is. But it is tucked away in the innards of your Sky router, and the router does broadcast them when it connects, so if we watch the output from the router we can deduce what they are. I’m assuming you have the standard white Sky fibre router, which looks like this:

The white Sky fibre router

Essentially you need to install software called Wireshark and use it to snoop in on the packets the Sky fibre router broadcasts when it starts up. Full instructions for that are available here:

How to get the Sky Username and Password for the Sky Hub SR101

Set up your new router

I can personally recommend the Asus RT-N66U. It’s not cheap, but it does pack a lot of cool features. You can get refurbed ones for about £70-80 if you keep a lookout. I got mine because I wanted to do things like use OpenDNS to filter content on my network (I’ve got kids and want finer-grained control than the blunt tool of the ISP filters) and run a VPN so I can access my network when out and about. It’s also fast (gigabit ethernet and 5GHz wifi-n) and stable.

To set it up for Sky you’ll need to install a slightly modified firmware. Merlin’s custom firmware for the Asus RT-N66U router is a minimally modified version of the standard firmware. All the changes Merlin has made are open source, if you’re paranoid you can read the source code. Instructions are on Merlin’s site; it’s really not hard and there’s apparently no risk of bricking your router.

Once you’ve got the new firmware installed go to the router’s admin page (which will be at something like in your browser) go to the “WAN” section and enter your Sky username and password into the Special Requirement from ISP > Manual client ID (for some ISPs). Here’s mine:



Note the single quotes, IIRC they are required, and don’t forget the | between @skydsl and the password. You may need to reboot the router and/or give it a bit before it connects, but it will. Enjoy your new router on Sky fibre!


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What is the Green Deal?

Posted in Green on April 23rd, 2014 by Andy
A cloudy green haze

Sometimes knowing what to do can seem like peering through a green fog…

The Green Deal is a government scheme to try and take some of the sting out of making green home improvements. The state of the housing stock in the UK is pretty dire, so we certainly need to do something, but is a Green Deal loan a good deal for homeowners? Well, yes and no…

How does it work?

Basically you as a homeowner make a booking with a Green Deal Assessor. This costs about £100-150, but you can sometimes get it for free. The Green Deal Assessor will have a bit of a look at your house, check your bills and make a bit of a rough estimate of the energy efficiency of your house. Based on this they’ll make some recommendations for improvements you could make that will pay for themselves in fuel savings. That last bit is important, it’s the “Golden Rule” of the Green Deal. You pay for the improvements by taking out a Green Deal loan, and the repayments on the loan aren’t supposed to cost you any more than you pay now, it’s all paid for through the efficiency improvements. The loan repayments are taken automatically out of your electricity bill.

The Green Deal can be used to fund anything from extra insulation to new boilers, solar panels, heat pumps, etc.

The assessor will also advise you of any Green Deal cashback grants that are available to you, it’s often worth getting an assessment done just to be eligible for these, even if you have no intention of taking out a loan.

Should I take out a Green Deal loan?

I reckon it’s like this:

You may notice that nowhere in this flow chart do I recommend getting an actual Green Deal loan. That’s for a couple of good reasons:

  1. The interest rates aren’t good. If you need to take out loan you can get a better deal from normal lenders like your bank or a building society. You’ll save money doing it this way.
  2. A Green Deal loan is tied to the property, so could make it difficult to sell your house. Buyers are understandably wary of taking on a debt incurred by someone else, even though the “Golden Rule” supposedly means they’d only be paying what they would have paid in the bills anyway.

So is the Green Deal pointless?


Green Deal assessments are useful, they help people decide what they should improve. Adding more insulation and draughtproofing is very cost-effective, and almost anyone will benefit from improving it but a lot of people don’t realise this. A Green Deal assessment should spell it out. The fact is you don’t need to spunk megabucks on green bling to save money and cut carbon.

Also, having an assessment done frees up Green Deal cashback funding you can use to subsidise improvements. Even if you have no intention of taking a Green Deal loan, it can be well worth your money to get an assessment done.


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Electricity Suppliers’ Fuel Mix 2013

Posted in Green on December 30th, 2013 by Andy
Wind turbines silhouetted against a sunset

How much of an effect do these things really have?

How clean is UK electricity really? How much cleaner is the supply from a “green” electricity company? Will switching to electric cars mean less pollution?

All these questions depend on the fuel mix of the electricity supply. The power plants operated by some power companies are much dirtier than others, and by law all companies are required to declare where they’re getting the juice they sell you. The list below is an updated version of the one I compiled last year.

SupplierNuclearGasCoalRenewOtherCO2 intensityCO2 emissionsCost on billExternal costCost including external
British Gas28%34%26%10%2%0.3791,251£521.21£59.32£580.53
Southern / Scottish Hydro / Swalec / Atlantic / M&S /Ebico1%28%54%15%2%0.6132,023£534.81£104.26£639.07
Scottish Power1%26%59%13%1%0.6402,112£531.99£111.27£643.26
Good Energy0%0%0%100%0%0.0000£533.72£1.82£535.54
Utility Warehouse0%51%34%14%1%0.5121,690£558.58£68.75£627.33
First Utility5%31%52%8%4%0.4701,551£581.42£106.03£687.45
Green Energy UK0%79%0%21%0%0.190627£498.96£10.55£509.51
Spark Energy5%31%52%8%4%0.6192,043£492.33£106.03£598.36


The supplier’s standard tariff was used, and does not take into account any discounts or special offers.

External costs are (in pence per kWh): coal = 5.4, gas = 0.39, nuclear = 0.48, renewable = 0.055, other = 6.05. (source: Pearce et al 1992). Fuel mix multiplied by this number gives the external cost, and the annual total shown above is for 3300kWh.

The Big Six

Between them Npower, British Gas, EDF, EON, SSE and Scottish Power supply 90% of homes in the UK, so the power they’re generating is the most important.

  • Npower: Once again, one of the worst suppliers. They manage to combine high prices with a supply that has actually got dirtier recently. Avoid.
  • British Gas: Rising prices and a somewhat less clean supply than last year has eaten into their lead over the other Big 6, but they’re still the best overall.
  • EDF: Snapping at BG’s heels comes EDF. They’re slightly more expensive but the carbon intensity of the power they feed into the gird has dropped even further, and they’re now the cleanest generator among the Big 6 by a long way. At 0.161kg CO2e kWh-1 they now supply genuinely low-carbon electricity to 5.7 million households. If you want a Big 6 supplier, you could do far worse.
  • EON: Their use of coal has leapt from 30% to 50% in the last year, and the numbers reflect it. Cheap, but definitely a generator that’s heading in the wrong direction.
  • SSE: The biggest supplier of renewable power to the grid is also one of the burners of coal, which erases all the good work on renewables.  Their coal use has also leapt this year, from 35% to 54%, which represents a huge amount of coal burned. Don’t buy your power from here if you like living on Earth.
  • Scottish Power: Saving the worst for last, Scottish Power claims the wooden spoon from Npower this year. Despite supplying good amounts of renewable power their heavy reliance on coal over gas makes them the dirtiest supplier on the grid.

Smaller suppliers

The big winner this year is Green Energy UK, who combine seriously low prices with the second cleanest fuel mix (base on natural gas an renewables). Only the 100% renewable Good Energy beat them on external cost, but can’t match their prices. Other honourable mentions go to LOCO2 and Ecotricity, both of which manage to beat all of the Big 6 on price and green credentials.

Less impressive are Spark Energy, who are cheap but very dirty, and First Utility who once again claim the dubious honour of being the worst supplier in Britain. If I was one of their customers I would really want to know why they seem to pay so much for the dirtiest power available, when it should be the cheapest.

Ovo’s performance looks pretty lacklustre, but like Ecotricity and Green Energy Uk they also have a 100% green tariff that would be well worth a look.

What is the “external cost”?

It’s an attempt to sum up all the different negative impacts that generating energy has, from carbon emissions and deaths from poor air quality, to destruction of forests due to acid rain. It expresses this impact as a cost in pence per kWh generated. In a fair world, the source of that damage (ie: the owner of the power plant and their customers) would pay for that damage, so by adding the external cost to the actual cost of  your power you can get an idea of whether cheap dirty power is a better deal for society than expensive clean power.

If you’re feeling really keen to offset this you could of course make a donation to a green project equal to your external cost.  Or you could sink it into a green crowdfunding project like the ones on Abundance Generation. Just a thought.

Pearce, D.W., Bann, C. and Georgiou, S. (1992) The Social Costs of Fuel Cycles, Report to 
the UK Department of Energy,
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How to make a Raspberry Pi media centre

Posted in Computers, Gadgets, Howto, Linux, Tech on August 21st, 2013 by Andy
A man wearing a t-shirt printed with "couch potato" and juggling several remotes.

We’re doing important stuff here.

I built a media centre PC a few years back and I’ve been happy with it ever since. It’s been running XBMC, which is an awesome free media centre package. But I reckon it’s time to get some Raspberry Pi in my front room.

Why Raspberry Pi?

  • It’s cheap!
  • It’s fanless (ie: silent)
  • It can push out full-HD video
  • It’s got HDMI (including sound and CEC) so only needs one connection to my TV.
  • It’s very low-power so can run constantly. So no waiting for it to boot up.
  • Customised XBMC builds are available for it, and are well supported.
  • I keep all my media on my network, so my media centre box doesn’t need any storage
  • It’s so small I can just velcro it to the back of the TV, removing a whole box from my TV stand.

How much will it cost?

  1. Raspberry Pi Model B: £32
  2. Plastic Case: £5ish

Which is less than the parts of my old machine are worth on Ebay. Ka-ching!

You’ll also need a power supply that can put out 5V on a micro-USB (I’m using a Kindle charger) and an SD Card to install the OS onto. I had both of those knocking about, which saves money. I also plugged my old media centre’s wireless keyboard into the Raspberry Pi’s USB port, just in case. In practice we can control XBMC with a tablet or smartphone over our home network, but a keyboard and trackpad can be handy during setup. You could ditch it after that and save a bit of power. There’s always SSH from another machine if you need to do anything fiddly.

Enough waffle. How do we do it?

Pretty simple, plug your SD card into a computer (one running Linux is easiest IMO), and download Raspbmc. Raspbmc is a ready-rolled bundle containing a very minimal Linux operating system and XBMC. Once you’ve downloaded the archive, extract it and run the installer script within as root. Full instructions for your operating system are here. Other similar systems such as OpenELEC are available, but I found OpenELEC to be a bit unstable. YMMV, as lots of folks highly recommend OpenELEC.

Then just plug the prepared SD card into your Raspberry Pi and power it up. Simple.

What’s good, what’s bad?


  • XBMC for the Raspberry Pi is pretty much identical to the PC version. It’s slick and easy to use.
  • HD video playback is perfect, right up to 1080p.
  • Navigating menus in XBMC is still pretty smooth, despite the incredibly puny hardware.
  • The system updates itself. All you’ll have to do is reboot occasionally.
  • The XBMC remote app for Android allows you to browse and control all your media files.


  • The RPi likes to fight with my Samsung Smart TV. I don’t know whether it’s the way Samsung have implemented CEC (aka Anynet+) or the way the RPi does, but I found it far easier to just turn off CEC control in my TV’s settings. After that everything worked perfectly.
  • You can’t power off the RPi with the XBMC remote (this is a hardware limitation in ARM). The easiest thing to do is just leave it running constantly, which is mildly wasteful, but only to the tune of about 3W (that’s about 26kWh per year).




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Lovefilm voucher codes: 2 free months

Posted in Random on July 10th, 2013 by Andy

Lovefilm_logo_V401920778Since getting a smart TV we’ve been trying out streaming from Loveflim and Netflix. We’re pretty happy with both to be honest.

If you’re thinking of trying it out I’ve got Lovefilm voucher codes for two free months:

  1. Go to
  2. Enter code: YGCH6GMEN
  3. You’ll get two free months of streaming or disks (or both), if you cancel before they bill you for the third month it won’t cost you a penny.
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ZOMG Fibre

Posted in Computers, Tech on July 9th, 2013 by Andy

We’ve got some new shiny, in the form of a new fibre braodband connection.
We bought a nice smart TV a little while ago, and unfortunately our pokey old broadband wasn’t up to the job of streaming video. I think the neighbours could hear us grinding our teeth as it buffered horrendously on even the shortest and lowest resolution playback. The whole problem was that we’re a good mile or two from our local exchange, and the way the streets lie I’d say we on the end of a piece of copper probably twice that length. Basically the bits and bytes were so shagged from the hike from the exchange to us that they just flopped down exhausted at our doorstep and were no use for anything.

But those days are no more! Behold the ludicrous speeds of fibre broadband. We’ve gone from about 3Mb/s down and 0.5Mb/s up to over ten times that. Shwing!

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How to control indoor air quality

Posted in Green, Howto on May 25th, 2013 by Andy

I recently blogged about how I solved an indoor air quality problem in my house by fitting a single room MVHR unit, but thought it might be useful to look into the different ways to tackle this common problem.

A family seated at the dinner table wearing gas masks

There must be a better way

What causes mould, condensation and humidity indoors?

The amount of moisture that the air can hold varies with temperature. Warm air can hold more water than cold air. This is known as the Relative Humidity. An RH of 80% means that the air contains 80% of the maximum for that temperature. Cooling the air would cause the RH to go up, until at 100% the air could no longer contain that water, and it would condense out. So we need to avoid very moist air from touching anything cold and causing condensation.

The main sources of moisture in your home are wet rooms (ie: showers), cooking, and the presence of people. These all release moisture which if not ventilated can build up. Besides humidity the other problems for indoor air quality include CO2, volatile gases, radon, outside pollutants, etc. However monitoring humidity is cheap and easy, so can serve as a useful proxy for indoor air quality in general.

How can we tackle a dampness problem?

The first thing to do is buy a cheap humidity monitor and see what your RH is. It’s very difficult to tell without one, as people are pretty insensitive to humidity. If you’re seeing above about 70% RH in winter, you should take some action.

Eliminate sources of moisture


This means doing simple things like putting lids on pots on the stove, or opening the windows while showering (assuming it’s warm enough!).

  • Pros: Simple, costs nothing
  • Cons: Limited effectiveness, especially in winter.

Mechanical Extract Ventilation (MEV)

This includes simple extractor fans in wet places like the bathroom or kitchen. These vary widely in price, with the more effective humidistat controlled versions costing several times that of the cheapest. The range of fitting options are wide, you can fit them through walls or windows or you can mount them in the ceiling and run a duct through your loft to the eaves.

The main drawback is that by simply chucking all your nice warm internal air out they create negative pressure which sucks cold outside air  in elsewhere. So while your indoor air quality will improve, your house will be colder. At current energy prices it is still cheaper to burn more fuel to replace the lost heat than it is to pay for a more expensive MVHR option (see below), but there is the comfort and carbon footprint angle to consider. Most extractor fans are also very draughty when not running, although ones with shutters are available.

  • Pros: Wide range available, can be very cheap.
  • Cons: Substantial heat loss

Positive Input Ventilation (PIV)


Essentially the opposite of MEV, PIV continually forces fresh air into the house, creating a slight positive pressure within. That air needs to have a defined exit path, so you’ll need continually open airbricks, trickle vents or MEV as well.

PIV units are often mounted in the loft where they draw air that is not quite as cold as external air, but if you’ve insulated your loft as well as you should have the difference will be pretty minimal. Effectively the have the same drawback as MEV. Since they run continuously the temperature swings will be less uncomfortable, but overall your heating bills will be higher. Some are available with heating elements to warm incoming air, but since this is straight resistive heating it’s a very expensive and dirty way to heat your home.

  • Pros: Effective, and don’t cause sudden temperature drops.
  • Cons: Same heat loss as MEV, or very expensive if pre-heating the air supply.



Dehumidifiers can get the moisture out of the air without venting it to the outside, and have the bonus that the dried air releases some heat, and is easier to heat than moist air. This would seem like a good option for a green home, if not for one major risk.

Excess humidity means that the home is not well ventilated enough. Besides moisture other pollutants such as CO2 can build up. While a dehumidifier can remove the moisture it doesn’t remove anything else, and excessive CO2 levels indoors can cause fatigue, headaches, etc. I would advise people to use dehumidifiers sparingly, and only to deal with point sources of humidity such as drying clothes indoors. Don’t leave them running continuously unless you are also monitoring CO2 levels. Unfortunately CO2 monitors can be quite expensive.

The better solution IMO is to ventilate, not dehumidify.

  • Pros: Tackles the problem directly
  • Cons: Not particularly cheap, risks masking air quality problems.

Insulate cold spots


Condensation will only form when air is allowed to cool so much that the water condenses. By eliminating cold spots you prevent this dampness from forming. Old windows and doors can be replaced or secondary glazing fitted, air leaks can be plugged, and cold spots on walls can be insulated (watch out for voids in cavity insulation, or bits that people forget to insulate like dormer windows and the ceiling of bay windows).

  • Pros: Often an easy DIY job, reduces fuel bills.
  • Cons: Not always easy to do, cures condensation but doesn’t actually improve air quality.

Whole house MVHR (Mechanical Ventilation with Heat Recovery)


This is the gold-standard solution. Air is extracted through ducts, passed over a heat exchanger and vented. Fresh air is drawn in and picks up heat from the heat exchanger to supply warmed air.

Generally it is impractical to retrofit a whole-house MVHR unless you’re doing a major refurb, due to the need to run ducts. MVHR also requires a high standard of air tightness in the house, which has to be designed into the structure of the building. MVHR is popular in high-tech Passivhaus eco-homes, but is very rare otherwise due to the four-figure pricetag.

  • Pros: Effective, quiet, comfortable, green.
  • Cons: Expensive, requires highly air tight house, requires duct runs.

Single room MVHR


This is a hybrid of conventional MEV and MVHR. A continuously running fan is fitted through the wall of wet rooms such as the kitchen and bathroom, and includes a heat exchanger to warm the supply air. Often an old bathroom extractor fan can be directly replaced with a single room MVHR, making them ideal for retrofit.

In my case I’ve found a single MVHR in the bathroom has been sufficient to control humidity for my whole house.

  • Pros: Effective, retrofittable, reduces heat loss.
  • Cons: More expensive than MEV while doing basically the same job.
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MicroSD storage madness

Posted in Computers, Random, Stupid trivia, Tech on May 18th, 2013 by Andy

 An giant 19070s hard the size of a man compared to a tiny microSD card sitting in someone's palmThis is a pretty mad picture. I remember the first PC I owned had a 202MB hard drive, a size that just seems laughable compared to that microSD card.

So where does it all end? Will we eventually be able to pack the entire internet into a pinhead? Physics wonks tell us there is a maximum theoretical amount of data you can squeeze into a finite amount of matter,  but it’s a lot. For the microSD card given above it works out to about 567 bits, which is about 6.2 trillion trillion trillion trillion trillion MB.

It turns out that the capacity of hard drives has been growing at an exponential rate over time:

Capacity of hard drives over time. Note the logarithmic scale...

Capacity of hard drives over time. Note the logarithmic scale…

So, if they keep growing at this rate when would that microSD card sized storage device max out? Well, if the biggest microSD you can get currently is 64GB then I make it 132 years. And what could that microSD card fit on it? Well, the entire data storage of Earth in 2013 is around 735 exabytes, and that would take up a smidge over 0.000000000000000000000000000000000000000001% of the space on this “perfect” microSD card.

So clearly things can get even smaller, and store even more. Watch this space.


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