February 28, 2018

Assembling and Testing electronic circuits. Preparation.

Before you start assembling a circuit in a working environment, there are some general preparations which you need to make. Since this is a work environment, it is covered by health and safety legislation. There might also be specific working practices defined, such as not working alone (in case of accident), only eating/drinking at designated locations in the workplace, clear access routes, etc.

Many chemicals and products which you work with can be dangerous (if ingested, heated, mixed with other products, or even if they are physically damaged. Legislation called COSHH defines some of the things you and your employer must do to minimise the risks, and you should have access to an Material Safety Data Sheet (MSDS) for everything you work with. You also need to be aware of risks from hot or cold materials, moving equipment and electrocution.

There will be instructions to describe the work you have to do. These can be detailed instructions for every step, or you may need to work with various types of schematic and standard procedures to complete the work. Within this, each operation may require you to use defined techniques for each stage. These may be documented, or you might be expected to use an accepted approach which is learnt by experience. Some working environments (aerospace for example) may have stricter requirements for these operations, requiring documentation and formalised regular training in technique. Regardless of the detail, the standards which you are expected to work to will be defined and you should take responsibility for ensuring that your work meets the standard expected.

It is important to use the correct techniques since the way that components are mounted and fixed can affect the safety or operation of a circuit when it is being used, long after assembly and testing is completed.

You must check that the tools you are using are safe and in good condition. This can include calibration and electrical safety testing (which both need to be repeated at regular intervals). You should know any risks specific to your workplace, and know how to act in case of an accident to make the environment safe, to summon assistance, and when to try to provide aid yourself without putting yourself in danger. If the task requires you to use a tool which you are not familiar with, it is your responsibility to raise this as an issue and avoid putting yourself at risk.

In addition to these items which will apply to every task, you need to prepare for the specific task. This is described in the next post.

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Electronics for Performing Engineering Operations

This is a NVQ course (7582), covering a wide range of topics.

I’m disappointed by the amount and quality of supporting material (a book published in 2012 – Grimwood, will be a little dated by now even if it was current when published). Courses are using circuit examples based on NE555 and 7805 type voltage regulators – These are 45 year old components and do not provide a good starting point for students entering the workforce in 2020.

The posts here are not answers to assessment questions, but provide background information which will help you with the assessments.

Please provide your feedback on the topics which you would like to see discussed and explained in more detail.

I’ve worked in designing prototype electronics (mainly radio-frequency circuits), including small production runs of up to 500 units for evaluation. I’m familiar with both the design, and manual/automated assembly and test. More recently, I’ve been working in ASIC/Integrated circuit design.

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December 29, 2016

Microbit Neopixel Christmas Tree

OK, so you’ve got your micro:bit RGB christmas tree from Andrew Gale’s kickstarter project. Its all soldered up ready to go as per his instructions but you’re not quite sure how to proceed.

First, use some croc-clip wires to connect the pads on the christmas tree to the pads with holes on the micro:bit edge connector. It is important to get the order right, and to avoid connecting also to the small pads between the main pads on the micro:bit. It doesn’t matter which colours you use, but normally 3V would be red, and 0V would be black.

  • Pin 0 to SOUND
  • Pin 2 to LED
  • 3V to 3V
  • GND to GND

Now you need some software. For a quick-start take this file directly from GitHub. Right click here and save-as (the file should be called tree.hex). Now plug your micro:bit into your PC, and copy the hex file to what looks like a flash storage device on your micro:bit. The yellow light should flash on the micro:bit as the file is transferred, this will take a couple of seconds. Now the program will start, and although the micro:bit display remains blank, the tree will have sound and light.

You can see the program (which is written in python) here on GitHub. We import both the neopixel module and the music module. These add extra functionality to the basic micro:bit, and they’re described here.

First, we initialise a neopixel on pin 2. This can drive several of the intelligent LEDs. They work in series over a single wire, and can be set to light each of Red, Green and Blue to different brightness. I am using 155 for each colour in turn which is a moderate brighness (255 is really too bright to look at safely).

Before starting to light the LEDs, we play the NYAN theme (non-blocking, so the program continues to run whilst the tune plays in the background).

We then cycle through all 5 LEDs and all 3 primary colours. Then we change the tune, and repeat.

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