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Free study courses from FutureLearn

19/9/2013

Futurelearn are offering free training places on short part-time courses. There’s a limited list to choose from but one that may interest the readers is an introductory course on Java programming.

The courses are run by leading UK universities, are completely free, and you can study at your pace.

The Java course starts early 2014, runs for 7 weeks and they suggest you will need to study around 3 hours per week – that should give me something to do on the train every day.

Full details and a list can be found here: https://www.futurelearn.com/courses

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Transistors and their specifications

16/9/2013

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Whilst attempting to repair a simple microphone pre-amplifier for a friend, the culprit was found to be a blown transistor. A quick internet search found the specifications of the device and it was then a simple matter to find a suitable replacement from what was available in the junk box.

Interestingly, my friend, who has only a casual interest in electronics, was bemused by all the Vcb, Vce, Ic and other details in the parameter tables.

So I did a quick drawing of a simple common emitter amplifier based on a NPN transistor and explained the different values.

Below is a sample specifications table for some NPN transistors. Notice the three BC107 transistors at the bottom of the list are from two different manufacturers, but their specifications vary quite a bit. For example, the Hfe (Small Signal Gain) of the TRU device is over four times that of the CDIL variant, but the CDIL variant has a higher maximum working frequency.

The parameter that most hobbyists are concerned about tends to be the Ic. This is the maximum current that the transistor can drive when a load is connected between the Collector and +Vcc.

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Shift registers

13/9/2013

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I've been a bit lax recently and whilst I've got piles of content that I need to complete and upload, pressures of starting a new job are taking their toll. I'm hoping that normal service will be resumed soon.

Anyway, I've uploaded an article (PDF document) that attempts to give the reader a brief introduction to shift registers. Theory is all well and good so there are some simple construction details for a PIC based project that can control up to 255 x seven-segment displays. All the source code and diagrams etc are supplied so the constructor can change the firmware to fit their own requirements.

UPDATE 20th Sept, 2013.... Just uploaded the correct version of the PDF file... sorry about that.

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Free study courses from FutureLearn

Transistors and their specifications

Shift registers

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