Monthly Archives: August 2016

Why You Can’t Use Resistors as a Voltage Regulator


Due to WordPress’s abysmal handling of code blocks this blog post is now hosted at https://majenko.co.uk/blog/

People, all the time, use a simple resistor-based voltage divider to change 5v into 3.3v. You see it all over the place. For instance, when you want to get your 5V Arduino to communicate with a 3.3V ESP8266 – you use two resistors (10K and 22K say) to drop the 5V of the Arduino down to the 3.3V the ESP8266 expects.

And that is all fine and dandy.

However I all to often come across people attempting to do the same thing to power a 3.3V device off 5V. After all, if you can use it for changing 5V into 3.3V for the signals, surely the same thing works for the 5V power to 3.3V, right? I mean, it’s the same 5V isn’t it?

Well, no. You can’t. Absolutely not. And it’s all because of the current.

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Dangers of Counterfeit Power Supplies


Due to WordPress’s abysmal handling of code blocks this blog post is now hosted at https://majenko.co.uk/blog/

SamPlugI thought I would take a look inside a power supply that I suspected was a counterfeit. See just what is going on with it.  This Samsung power supply was making strange things happen with my phone while it was plugged in. Yes, it charged the phone fine, but it made the touch screen go all screwy, and I suspected it was a rather noisy switcher in it. I had bought it from eBay for next to nothing, so I am expecting it to be somewhat nasty inside.

Guess what? I was right.

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Diagnosing Arduino Problems in Linux


Due to WordPress’s abysmal handling of code blocks this blog post is now hosted at https://majenko.co.uk/blog/

Getting Arduino and Arduino-like boards working properly under Linux can be a troublesome task if you are not familiar with how Linux works.

So I am going to introduce you to some of the basic tools you will need to work out why your board isn’t working as you’d like it to work. Continue reading

eBay Volt/Amp LED Meters


Due to WordPress’s abysmal handling of code blocks this blog post is now hosted at https://majenko.co.uk/blog/

s-l1600I thought the other day I would grab a couple of these cheap little LED volt & amp meters modules you see on eBay. 30V, 10A, red and blue LED displays. Funky little things. I felt I should take a look at them and see just what they are, what they do, how you use them, etc.

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Measuring Arduino Internal Pull-up Resistors


Due to WordPress’s abysmal handling of code blocks this blog post is now hosted at https://majenko.co.uk/blog/

The Arduino (and many other boards) have a very useful time-and-cost saving feature ideal for when you are working with buttons and switches – namely internal pull-up resistors on the GPIO pins which can be enabled / disabled at will in software. This means you don’t have to clutter your board up with pull-up resistors of your own for all the buttons and things, and also means they can be turned off and on to give your design much more flexibility. Continue reading