Wednesday, February 23, 2011

5 amp fuse - cowboy electrician detector

Most home appliances do not require more than 5 amps of electrical 'draw'.

However hairdryers are a notable exception. Hairdryers which have a rating of more than 1200 watts will need a fuse larger than 5 amps.
So if your hairdryer says 'Salon rated 1800 watts' or 'Salon quality 2000 watt AC motor' then you best throw a 13 amp fuse in that plug.

Other appliances that might require 13 amps, are things that involve a large physical motor, perhaps a washing machine, or a high powered vacuum cleaner.

An industrial heater or a spin dryer might require that sort of 'draw' when in 'high heat' mode.

What hairdryers will run okay on a 5 amp fuse? The smaller travel hairdryers or something small / light which you have given your daughter, may well be rated 1200 watts or less (for that a 5 amp will do fine)

Old televisions that are more than 3 years old but less than 10 years old, do NOT require a large 'draw', to power the emitter at the back of the Cathode Ray setup. Newer televisions are often better again, and can usually be fitted with 5 amp fuses (see next section)

Power washers that claim to be powerful enough to clean outside concrete, with a blast of water ... yep that will likely be more than 5 amps worth.

Your laptop is likely to require less than 1 amp (more details toward end of article)


What in my home should be fitted with a 3 amp or 5 amp fuse?:

Bedside lamps and reasonably modern oil heaters, should not require more than 5 amps.

For some a 3 amp fuse will be sufficient (check the booklet)

( Readers from outside the UK, may have a different granularity with regard to plug fuses, or adopt a 'one fits all' approach )

LED Televisions (even up to 32 inches) rarely require more than 1 amp!!

Older televisions (we have a 28 inch from 2005) require less than 3 amps mostly.
( The Panasonic 28DTX1 in the link above uses < 1 amp and 90-120 watts)

Look on the back of the Television and read off what it says if you are unsure.
( A good television from a reputable manufacturer, should have the Volts and Amps indicated on the rear. )

Failing that a decent Electricity monitor can tell you right away what the Television is using.


The Handyman versus the Electrician:

A reputable Electrician in the UK should never be without a range of fuses (3 amp, 5 amp, and 13 amp), and should fit appropriate for the equipment.

If you use an Electrician and s/he fits a 13 amp fuse to a 5 amp rated device, then you should ask yourself "Is this Electrician lazy or irresponsible?"


Why is this important?
As electrical devices get older they sometimes become less reliable and malfunction. The first indication might well be a warm cable or a blown fuse.

A device fitted with the correct rated fuse, will possibly indicate it's malfunction to you earlier.

( I do not own a pair of hair straighteners, however if I did, and they were rated at 4 amps, but regularly tripped a properly fitted 5 amp fuse, then I would certainly want to either replace them, or have an electrician do a safety check. )


Elderly relatives and Electrical safety:

There are various reasons why the Elderly are considered for 'priority home checks' by the Fire Department. Those reasons might well be communicated to you if you ask.

If you are visiting an Elderly relative, then take the time to help out with replacing old equipment, or enquiring about Electrical items that have seen better days.

In particular it takes only minutes to check the fuse ratings for those items and to flag up any 13 amp fuses you see.

Did the handyman fit them? Does your great Aunt or Grandfather have a ready supply of fuses, or did they just buy a pack of 13 amp and use them whatever?

A four pack of each should do, and will cost you very little from the local store.
Keep them together and mark the bag so they are conveniently found when needed.


If the device was overrated (fitted with a 13 amp fuse), then correct things and mark the plug to help in future.


This 750 watt Oil Filled (Mini) Radiator I own 'draws' 2.88 amps.

Probably a 3 amp fuse would have done, however there would be almost no tolerance there. Giving a 2.88 amp device some headroom up to 5 amps is probably a lot safer still than fitting a 13 amp fuse.


Laptop peak usage - expect your laptop to use no more than 1 amp:

If your laptop is fitted with a 13 amp plug, then I am pretty sure this fuse can be replaced with a lower rated fuse (check your laptop booklet in the section 'specification' if unsure)

Measured at the plug using an energy monitor, here are examples based on my Dell Inspiron 15 inch laptop:

  • Before boot cycle startup 0.02 amps
  • Normal usage 0.234 amps
  • Watching pre-recorded TV online (BBC iPlayer) 0.283 amps
  • Normal usage with cdrom drive spinning 0.318 amps
So that Dell Inspiron 1525 uses between a quarter to half of 1 watt and no more.

Worth a check what is in the plug at the moment:


...which is overrated as 3 amps is easily sufficient for my laptop, so a quick replacement is worth my time.





So now the laptop which draws half an amp (max), is fitted with a properly rated fuse (3 amp fuse).



Notes and further reading:

Do check the booklet when you purchase a new device.
That Oil Filled Radiator which draws 2.88 amps, came fitted with a 13 amp fuse!


A proper rating of fuse in the plug should help avoid the cable or device warming excessively in the case of older devices / malfunction.
This should make you feel safer in your home knowing that you have taken a practical step towards a known fire safety issue.
Some Electrical devices have an 'internal fuse' which is designed to protect the internal electronic circuitry.

Even with an internal fuse present, it still makes sense to stop the cable becoming excessively warm. This is particularly important if you are the type to hide cables, perhaps just under the edge of a rug or concealed at the carpet edge

Thursday, February 10, 2011

android - be discerning at lower end

Here is what to look for (as reasonable minimum) in android tablets, if you have £200 or more to spend:
  • 3D graphics support (OpenGL ES)
  • 256MB ram
  • SD card slot (or microSD at a push)
  • Android 2.1 or later (2.3 or later for WebM)
Here is what you can get if you halved your budget:


This advert was in an 'offers' sheet posted through the door. At the time, I remember thinking that the specification is value for money, but really at the low end of what I would want in a tablet.


If you only had £100 to spend would I recommend this tablet?

Well I think it ticks quite a few boxes for what it costs (about the same as 60 loaves of bread in UK)

When looking at a tablet it is all about budget. Firstly are you looking 'low range', 'mid range', 'high range'. Putting this as a car analogy, are you wanting a cheap compact (Vauxhall Corsa or similar), a mid priced saloon (Ford Focus), or a fast roadster (BMW Z4).

Staying with cars ... if you have £8,000 in your pocket, it is no good rejecting a Corsa because "It's not a BMW Z4"


That Elonex tablet and why it is not £200:

Going back to my 4 point test:
  • Does not have 3D graphics
    [ probably fine for watching movies and a bit of light browsing, however   Angry birds and newer games might not be available for the device ]
  • Has 128MB rather than 256MB
  • Has microSD which is okay.
    [ Full sized SD capability would be better ]
  • Android 1.6
Android 3 is now out. If you want to buy Android 2 devices then okay, but as Android 2 came out late last year, buying Android 1.6 device needs to be considered carefully.


What does a newer version of Android bring?

Perhaps a slightly slicker interaction, and improved power consumption from the same battery unit. More details in the link at the end of this article.


Elonex and December 2011:

This might be a little demanding, but I would not be surprised if in December this year Elonex for £99 ticked all the boxes :)

It is the way in technology that components get cheaper generally, and software technology develops quickly also.

The observant amongst you will have noticed that in my quick review of the Elonex £99 tablet, I failed to mention the keyboard / docking setup.
What a great little feature!

Maybe the build quality is not brilliant, but again going back to budget, for £99 Elonex offered a 720p capable 7" tablet with HDMI output.

It would be hard to argue represented anything other than GREAT VALUE.


My own tablet wants and likely purchase:

I am in no hurry to buy a tablet. I will be interested to see the situation around December in the coming year.

Probably I will still not buy, but in 2012 I will be looking at how 'free and open source' the available tablets are, and choosing one then.


Press coverage and "It's not a blah" type responses:

There are some in the media who have a favourite tablet.

Nothing will change that, and why should it. If I already owned a tablet and thought it was the 'bees knees', then it would be unlikely to be unsettled by a new arrival.

However what is inexcusable is for tech reviewers in major newpapers or online sites (BBC click) or similar, to disparage a £200 tablet because it cannot match a £500 tablet.
Refer back to my car analogy, for a reminder on why it is just nonsense to do so.

There is a premium tablet out now, from Motorola, named Xoom. I find it laughable that some of the same journalists will now say things like:

Unfortunately, at £nnn the tablet could end up as representative of the exclusive, expensive and elitist toys collected by tech's early adopters

So what the reviewer is really saying is "I already have my favourite".

Reviewer: Show me a £200 tablet, and I will fail to see it's merits, and just launch into a comparison of the new tablet against my favourite.

Reviewer: Show me a $800 tablet, and I will fail to see it's merits, and just launch into a comparison of the new tablet against my favourite.


Tablets as commodities and the Tesco / Asda launch:

Right now in the UK, the budget tablet market is pretty fierce.

[ Which is great for the consumer :)  ]

The £80 to £150 bracket in particular is being targeted by Tesco and Asda.

Do read the checklist at the beginning of this article and know what you are buying. If you just want a bit of light browsing and do not currently own a computer a tablet in this price range might represent excellent value for money.

It will not set your world alight perhaps, however as a useful piece of convenience, it might be hard to find better value.

If you can afford a Samsung Galaxy Tab or a Dell Streak or a Motorolla Xoom, then your options are much wider.

However it is important to be honest about your usage. Would you regret paying £500 for a tablet and rarely using it, or would you get better value paying more or less than that amount.

The choice, as they say, is yours.


Notes and Further Reading:

In the main article I did not expand on why I preferred SD card slot rather than microSD. An 8GB SD card will be slightly cheaper that an 8GB microSD card.

Also, some people, especially those who have dexterity problems, or who have deteriorating sight, might find microSD just 'too fiddly'.

Thursday, February 3, 2011

debian squeeze - xfce panel disappeared?

Debian squeeze, is a debian version that I joined early.

In choosing to use 'beta' software, you will run across an occasional bug.

Mine was the loss of the xfce panel, which did cause me an issue for an hour or so.

Debian production releases are generally very good, so do only choose to play 'beta' if you are prepared for a hiccup once in a while.



Loss of xfce-panel, the cause, and how to fix:

The probably cause was using a KDE application when my desktop is Xfce.
( Often this is not an issue, but sometimes it is. )

In short I installed choqok identica client, even though I do not run a KDE desktop (more on this later)

The big problem:
The application failure killed the program xfce-panel and I had no obvious way to restart it!

Help! my xfce panel is missing!


The fix (seems obvious now):
Open a terminal and start xfce4-panel manually.

( The untidy output from xfce4-cpugraph-plugin can be ignored as noise )


The permanent fix / check:

Xfce session can be set to always start 'xfce4-panel', and probably should be this way by default:


Session shows you what is running and the 'Restart Style'

Ensure (using the Application Autostart tab) that xfce4-panel is set to 'Immediately'

Once this is set to 'Immediately', you should be safe in the knowledge that a simple reboot will create a new session that autostarts xfce4-panel.

It should not take the loss of your panel to have such a desirable setting, but at least now you know where these sort of things are located :)

Xfce Menu --> Settings --> Session and Startup

( Above is where you will find how to change those preferences shown above )


Final Gotcha and Kiosk mode:

There are two ways of saving the session - (1) Shown above the 'Save Session' button within the Startup list screen
...and...
(2) The ticked box during Logout 'save session' prompt

Because you have started xfce4-panel from a terminal, then pressed 'Save Session' button, then most likely killed the terminal with (X)....

...if you then have 'save session' ticked when you see the logout prompt, then you will have undone all your good work!

Just this once, ensure you logout with NO TICK when the logout prompt is displayed.


But none of this worked for me as I just kept getting warnings about kiosk mode?
There is a bug in the beta for Debian 7 (wheezy) which seems to trigger kiosk mode if you attempt to manually start the panel from the clickable menu, rather than as I suggested (from a terminal).

If you get warnings about Kiosk mode, then recap on my instructions above, and avoid starting the panel by clicking a drop down menu - DO IT via TERMINAL


Xfce users running KDE and Gnome programs:

In short your mileage will vary.

You can go some way to having maximum compatibility by installing the entire KDE and Gnome libraries and desktop. Although this sort of defeats the object of running an Xfce 'light' installation!

You should maybe consider having these checkboxes ticked:




If you find yourself worrying about this kind of thing often, then perhaps you really should be running a full KDE or Gnome desktop in the first place.

Xfce is an excellent desktop, however it really depends on how _you_ use your computer. If it is not for you then try an alternative. At least with GNU / Linux you have these choices available to you :)


Notes and Further reading:

Would my issue have occurred had I not been using 'beta' software? Maybe, but it is hard to say for sure otherwise.

Would my issue occur, if I choose to play nicely, and start all the services that KDE relies upon in every session? Probably.

( If I have made this sound in any way like it is KDEs fault, then that is not my intention in this article. My aim was merely to introduce a discussion about compatibility based on an individual experience. )


My install log of choqok, showing the version which I think was not entirely happy with my 'light' Xfce environment:

2010-12-02 20:50:52 install choqok  0.9.81-3
2010-12-02 20:50:52 status half-installed choqok 0.9.81-3
2010-12-02 20:50:52 status half-installed choqok 0.9.81-3
2010-12-02 20:50:52 status half-installed choqok 0.9.81-3
2010-12-02 20:50:52 status half-installed choqok 0.9.81-3
2010-12-02 20:50:53 status unpacked choqok 0.9.81-3
2010-12-02 20:50:53 status unpacked choqok 0.9.81-3
2010-12-02 20:50:57 configure choqok 0.9.81-3 0.9.81-3
2010-12-02 20:50:57 status unpacked choqok 0.9.81-3
2010-12-02 20:50:57 status half-configured choqok 0.9.81-3
2010-12-02 20:50:57 status installed choqok 0.9.81-3

Wednesday, February 2, 2011

Debian Squeeze - free and non-free - Realtek Ethernet

With debian (6.0) squeeze release just days away, I have been following some of the news closely.

My interest is in free software that can be modified and distributed under reasonable terms, and much of what Debian does I like.

The removal of non-free firmware from the Kernel was announced a month ago.

Truly free firmware has been coming on leaps and bounds recently, particularly with the Broadcom commitment.

Michael Hurlston, Senior Vice President & General Manager, Broadcom's WLAN line of business
had this to say:

"There is no question: Linux has become a major platform for communications
devices and technologies"
The announcement means Broadcom are now a member of the Linux Foundation, and will work closely with developers to release driver code that can be used, modified, and distributed as appropriate.


But what about existing hardware?

Good question. If you already own a computer then it has a number of devices which are driven by firmware.

Will all those devices work with the stock Debian Kernel? Mostly.

There are some (mostly older) devices which have been superseded or where the company has gone out of business, that might cause a problem.

Thankfully hardware suppliers (like Broadcom) are willing to get involved properly with their current product range, and in some cases produce retrospective drivers also.


But what about Realtek Ethernet cards?

Here are some messages following my kernel update earlier:

update-initramfs: Generating /boot/initrd.img-2.6.32-5-amd64
W: Possible missing firmware /lib/firmware/rtl_nic/rtl8168d-2.fw for module r8169
W: Possible missing firmware /lib/firmware/rtl_nic/rtl8168d-1.fw for module r8169


If you have these messages appear during an update, then do not despair, it could mean nothing other than a warning.

What is worth doing, is installing discover and finding out exactly what is in your system:

apt-get install discover

Running discover should tell you a fair bit about your system:


The network card information should be in there for you to check. For me it shows that the card is in fact a Realtek, and gives me a best guess at the model number ( RTL8111 or RTL8168B )

Now I will reboot and ensure my networking initialises properly after the update.

And everything was fine.

If I was unfortunate enough to have older hardware, that did rely on non-free firmware, then I would have to take some more action.


Links and Further Reading:
Note: If you work in a large company / college and know for sure that all your computers include firmware Ethernet cards, that only have non-free firmware, then you should perhaps download the unofficial cd image mentioned in the final link above.

( There is an alternative to 'discover' in the package 'hwinfo', but all other alternatives I looked at gave me a 'non-free' feeling. )