Mar 102015

This is the case study to prepare for the Cambridge Nationals in ICT R001 exam in June 2015.

Download here: Cambridge Nationals in ICT R001 pre-release June 2015 (685)


The exam has two scenarios that are based on a computer animation business. On first glance, the following appear to be likely topics for exam questions:

  • Computer graphics
  • File storage, security and backup
  • Input/output devices
  • Collaborative working (e.g. VoIP/Skype and Wikis)
  • HTML forms and types of form fields (e.g. text field, select list, etc.)
  • Data validation (e.g. format check, range check, etc.) and verification (e.g. double entry)
  • Social networking

I will create a more comprehensive revision list in the coming days.

Feb 242015

I live in a rural village with limited broadband options. When we moved here a year ago, we chose BT Internet and now pay £17.00 per month broadband fee. We get a download speed of about 6.8 Mb/s and an upload speed of about 0.36 Mb/s. This is adequate for general web browsing and emails but is less than ideal for streaming videos and large upload/downloads.

We received a letter from BT this week with the subject “Your account review”. It recommended an upgrade to BT Infinity (only recently available in our area) with the following features:

* Speeds of up to 5x faster than the average speed of standard UK broadband
* The Infinity Hub, with the fastest wi-fi technology in the UK (£6.95 delivery)
* Streaming with less buffering

Apart from mentioning the cost of posting the hub, no other costs were mentioned so I thought I’d give BT a call (0800 011 3739).

The BT sales rep confirmed that BT Infinity was available in my area and they could guarantee 39-40 Mb/s download and 9-10 Mb/s upload. This seemed very specific, but they said they were confident of the speed due to my proximity to the exchange.

Before haggling, I was offered the following deal:

£23.00 per month
£6.95 delivery charge for router
£30.00 activation charge for BT Infinity

After complaining about the poor download speeds on my existing contract, I was offered an improved deal:

£10.00 per month for the first 3 months
£23.00 per month thereafter
£6.95 delivery charge for router
£30.00 activation charge for BT Infinity

I then haggled some more and the BT sales rep extended the discount period to six months:

£10.00 per month for the first 6 months
£23.00 per month thereafter
£6.95 delivery charge for router
£30.00 activation charge for BT Infinity

I know that much better introductory deals exist for new customers but I’m reasonably happy with this offer. I placed the order and should get the new service in about a week.

I’d be interested to know whether anyone has been offered better deals.

 Posted by at 6:55 pm
Feb 142015

This week I received a cheap GPS module that I ordered from a supplier on eBay.


The module cost £7.65 including delivery from China and was advertised as follows:

Ublox NEO6MV2 GPS Module Aircraft Flight Controller For Arduino

The seller listed this unit as Power supply 3V – 5V with no mention of logic levels; however, the schematic suggested this was probably a 3.3V device.


Wanting to confirm the logic levels I hooked the GPS up to a 3.3V power supply. My oscilloscope showed the RX/TX pins are 3.3V level. I then repeated the test with a 5V supply and the logic levels stayed at 3.3V.

To make this absolutely clear, the GPS module that I purchased can use a 3.3V or 5V power supply but the data transmission is 3.3V and therefore not compatible with most Arduino boards which use 5V logic. Connecting the module to an Arduino Uno (for example) may result in damage! The module is however compatible with the 3.3V logic used on the Raspberry Pi. If I wanted to use this GPS module with a board that uses 5V logic then I would use a level shifter.

Nov 042014

I used to import goods to the UK and sell them on eBay as a small part time business. When I contacted eBay to revert my Business Seller account to Private Seller status they refused and so I have continued to use the account for the occasional private transaction. Having retained my Business Seller status, I received the following email today:


What’s changing?

From 1 January 2015, new EU legislation is changing the way VAT is charged on electronically supplied services, such as your eBay fees.

If you’re not a business seller, eBay will charge VAT at the rate of the country where you’re based (for example 20% for the UK) rather than the rate of the country where eBay is based (15% for Luxembourg up until 31 December).

Read the full message here.

To be honest, the full meaning of this message is not at all clear to me and is the subject of some online discussion. Like others have mentioned, I’m hoping that eBay will clarify the situation for holders of Business Seller accounts who are not VAT registered.


 Posted by at 5:23 pm
Oct 152014

Budget web-hosting packages frequently attract negative reviews, but for every one dissatisfied customer I bet there are ten who are quietly content. With that in mind I thought I’d write my own review of Hostmonster to let you know why I have renewed for another 36 months of web hosting.

Firstly, I should point out, nowadays I have very little interest or time for editing or managing websites and only keep them online for the modest advertising revenue that they provide. I have a full-time job doing something else, and for me it would be pointless in investing money in high-performance web hosting packages as I only run low-traffic web sites of a few hundred visitors per day. These web sites arose when I had more time on my hands; however, even at peak demand (or personal ambition) the hosting resources have been adequate for my needs.

For a monthly outlay of $12 (or much less – more about that later) Hostmonster can provide web hosting with all the features you probably need to host a modern web site. PHP, MySQL databases and multiple domains are supported as standard, and SSH shell access comes on request. Hostmonster provide unlimited storage and bandwidth but on a shared server performance is limited.

Some people may criticise performance or support at Hostmonster, and whilst I realise the performance is not super-fast what do you expect for a few dollars per month? On the other hand, my experience of support and the real-time chat feature at Hostmonster has always been outstanding. As a Hostmonster customer since 2006 I have never been left waiting and the service has always been knowledgeable and courteous. Moreover, I have never had to chat online with someone who was blindly reading from a script (of course, they do have some set questions) or had a poor grasp of English.

My only bugbear with Hostmonster has been their charging policy which in truth is probably no different from most other budget web-hosting companies. Hostmonster provide very cheap hosting in the initial term but then increase the rates on renewal. New customers are currently being offered the Plus package at $6.49 per month (advertised as: “normally $9.99”) but recently I was offered renewal at $11.99

To be quite honest, the difference between $6.49 and $11.99 is not that significant for me and if I had to renew at the higher amount I would have done so. I also understand business practices and why the initial term is there to attract new customers. I had my eyes wide open when I signed up and I benefited from the promotional rate at that time and I’m not one to cry about it now. Nevertheless, two days ago I used the Live Chat feature and with not much effort got the fee discounted to $9.99 and then $7.99 per month (plus VAT at 20%).

So if you don’t like Hostmonster for whatever reason, my advice is to move on but don’t expect much better unless you pay a lot more. If you read any rave reviews online (Hostmonster, or otherwise) I’d suggest a big pinch of salt if there is any possibility of an “in-house” review or affiliate link being paid. Be warned: most of the positive reviews I have read include an affiliate link.

There is no affiliate link on this page and I’m not even going to link to Hostmonster as I’m sure you can find them without my help. Hostmonster apparently pay $65 per referral but I’m not going to bother as you probably wouldn’t click anyway, and instead you can enjoy my honest, unpaid and impartial opinion. Hostmonster provides a feature-rich package with modest performance but good service that has kept me happy for eight years and hopefully three more years to come.

Good luck with choosing a web hosting package.

Feb 022014

Cheap laser pointers abound in many different products. I recently purchased a handheld infrared thermometer and it included a red laser pointer for sighting purposes. The first thing my mother asked was, “Is it dangerous?” to which I replied the standard “no” but how can I be so sure?

GM550 IR thermometer

According to the product markings it uses a “safe” Cat II laser. It also had markings for CE and FDA approval but then again it was a cheap product made in China.

I had a quick search online for how to check laser pointer safety but drew a blank for low-power red laser pointers. I did on the other hand find a useful academic paper written in fairly accessible language identifying concerns and how to check green laser pointer safety. It may be worth a read to check whether any of the concerns raised and methods used could be relevant to red laser pointers.


An inexpensive green laser pointer was found to emit 20 mW of infrared radiation during normal use. This is potentially a serious hazard that would not be noticed by most users of such pointers. We find that the problem derives from an unsafe design, and describe a simple method of testing for it using common household items.

 Posted by at 7:12 pm
Feb 012014

This week I bought a cheap GM550 Infrared Thermometer on eBay. There were many models to choose from but this one appealed to me due to its low price (GBP 11.35) and stated measurement range (-50 to 550 C). Other cheaper units exist but they have a lower maximum temperature (typically 380 C) which may not be adequate if I need to measure stove and incinerator temperatures.

The GM550 thermometer has a resolution of 0.1 C and claimed accuracy as follows:

 0 C to 550 C +/- 1.5 C or +/- 1.5%

-50 C to 0 C +/- 3 C

* Whichever is greater

According to the specification, normal room temperatures should be measured to about +/- 1.5 C. Temperatures below freezing are much less accurate (+/- 3C) and the highest temperatures should be within +/- 8.25 C.

I have compared room temperature readings taken with the GM550 and an Oregon Scientific digital thermometer (a domestic thermometer) and found the readings to be very similar, typically within 0.8 C.

The GM550_User_Guide was written in surprisingly good English and was easy to understand. It explains that this thermometer has a preset emissivity value (0.95) and that shiny and polished surfaces must be covered with masking tape or flat black paint before readings are taken.

The GM550 looks and feels very well made and appears to function well. The LCD screen is bright and easy to read, and the unit casing is made from rigid plastic that does not flex under normal use. The thermometer fills your hand and has gives the impression of being a good quality device. If you want a cheap non-contact digital thermometer with a wide temperature range then this unit may well be suitable.

Jan 012014

I finally got around to trying out my ENC28J60 Ethernet adapter with an Arduino micro-controller. These adapters are very cheap (about 2 GBP on eBay) but are frequently considered difficult to use compared with a “standard” Arduino Ethernet shield.

I connected the ENC28J60 adapter to an external 3.3V power supply (with common ground) and measured the current draw at about 108 mA. In case it is not clear, this measurement confirms the ENC28J60 draws too much current to be powered by the Arduino 3.3V pin.

I downloaded the Ethercard library which provided some simple examples to create a web browser, test DHCP, etc. So far, these have all worked as expected and the card has proven much easier to use than I had initially supposed.

I have been playing about with email access for the Arduino which involves a simple PHP script that I have posted online. This allows the Arduino to request the page and thereby send an email. This could be used to send an alert or some data by email.

Dec 302013

I’m sharing this instruction book (with circuit drawing / schematic) for the Farnell L-Series Bench Power Supplies in case it is of use to anyone. These bench power supplies are frequently available on eBay (e.g. Farnell LT-300T dual power supply 0-30V 0-2A) but they are old, probably dating back to the 1970s.


Example model numbers:

  • Farnell LT-300T
  • Farnell LT-301
  • Farnell LT-302

Download the instruction manual: Farnell L-Series PSU

Oct 202013

I bought one of these pressure sensor breakout boards from a Chinese supplier on eBay.

GY-65 BMP085 pressure sensor

The board has a BMP085 barometric sensor, 662K voltage regulator (3.3 volts) and two 4.7K resistors. It has three other components that I have not identified. I presume the resistors act as pull-ups on the SDA and SCL lines for connection to the I2C bus.

I have tested the breakout board using 3.3V and 5V power supplies. I used an Arduino sketch to scan the I2C bus and found the pressure sensor at 0x77. I tried the Adafruit BMP085 driver and it appeared to function correctly.

  • VCC – 3V3 or 5V
  • SDA – Arduino analog 4
  • SCL – Arduino analog 5
  • XCLR – (no connection)
  • EOC – (no connection)
  • GND – ground

GY-65 BMP085 pressure sensors are available on eBay for less than 3 GBP including delivery.