Dr. Monk's DIY Electronics Blog

Open Source hardware, Arduino, Raspberry Pi, BeagleBone, DIY electronic construction, reviews, projects, how-tos and recipes.

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Testing the micro:bit's Analog Inputs

The BBC GPIO connection rings (labelled 0, 1 and 2) of a micro:bit can all be used as analog inputs.You might think, that as long as you are careful to to exceed the 3V input voltage limit, then you can measure any low voltage whatever the source. Perhaps a photoresistor in a voltage divider arrangement with a fixed resistor. While this is basically...

Unit Testing and Arduino

When I worked in software, I was an early adopter of agile software development (eXtreme Programming) and so have always loved unit tests and TDD. Like many people from a software background, when I first started programming Arduino, my instinct was to write frameworks, patternize and objectify my code. Then I realised that I have 32k of program space...

Making Protective Face Shields with a K40 Laser Cutter - Part 3

Part 1 Part 2We finally had a chance for the household to go ahead and make some shields.CleanlinessThis was tricky, I don't have gloves, but do have a face mask each that covers our mouths and noses. So, I would not count these masks as sterile and as such have been careful to pass on that information to recipients.So we had frequent hand washes and...

Making Protective Face Shields with a K40 Laser Cutter - Part 2

In part 1 of this post I looked at laser-cutting the plastic band. In this post, we can now attach the clear A4 sheet to the shield.I used this from eBay with a thickness of 140 micros for the visor, which seems about right.The A4 clear 'acetate' sheet fits in landscape aspect ratio and is punched with 4 holes. I used one of these:.. and put one pair...

Making Protective Face Visors with a K40 Laser Cutter - Part 1

This blog documents my efforts to make protective face masks using a low cost K40 laser cutter using Kitroniks visor design.The A4 'acetate' sheets for the transparent shielding bit haven't arrived yet, so consider this post a Part 1 , dealing just with making the strap.Early indications: Yes, it's feasible - if you have a K40, give it a go.K40These...

Installing OpenCV 4 on a Raspberry Pi 4

I have recently been updating the Computer Vision chapter of the third edition of my Raspberry Pi Cookbook. Way back when I was writing the seconds edition, I decided to use the SimpleCV wrapper to OpenCV because it was -- well very simple to use.SimpleCV is no longer maintained and in any case requires Python2. So the chapter's code needed to be changed...

Making an SD card out of 1960s transistors

Reading about flash memory, I was staggered by the astronomical number of transistors in such a small place I decided to see what it would take to make one of these using 1960s technology.     Flash Memory: Lets go with a modest 32GB micro-SD card.Transistor: I'll use a TO-18 package transistor. If like me you are from the UK and of a certain age, then...

Arduino Air Quality Monitor

I've recently spent some time developing the MonkMakes CO2 Sensor for micro:bit and have spent a fair amount of time researching into indoor air quality. It struck me that I actually had no idea how healthy (or otherwise) the air is, in the house that I both sleep and work in. Time for a project! What's more I can reuse some of the sensors that I have...

Review and use of: Katsu ZD-8915 Desoldering Station

Desoldering through-hole components with two or three legs, is pretty straightforward. Apply heat and some fresh solder to the underside and pull them out from the top. But when it comes to chips and modules with more pins, this approach doesn't work. Some people manage to master the use of the small pen-shaped 'solder-suckers'. The idea is that you...

Cuban Makers at "Copincha" in Havana

Last week I found myself in front of a room full of Cubans in Havana, delivering a course on Arduino in broken Spanish. Was this a variation on the kind of dream where you are sitting down to an exam without having done a stroke of revision? Or the dream where you find yourself at work having forgotten to put on your trousers? The sequence of events...

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