Posts tagged with guide - page 2

XKCD's "Now" Coded in JavaScript

I love XKCD’s web comics, they always give you a new way of looking at something and a laugh to boot. Yesterday at work I came accross the Now comic. It shows you at a glance what countries are in business hours, or outside them. The image is rendered on the XKCD server and updated every hour when you refresh your page.

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Setup Mass Dynamic Virtual Hosts on Nginx

Apache has a handy feature that allows you to dynamically serve a domain without having to create a virtualhost for each time, called Dynamic Virtual Hosts. Nginx doesn’t have this feature built in, but it does gives you the tools you need to to set it up in no time. Here is a guide to how I got it working on my server after I transitioned my site from Apache to Nginx.

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PWM Exponential LED Fading on Arduino (or other platforms)

For a project I am working on I needed to dim a LED strip light using the PWM (pulse width modulated) outputs on an Arduino. The most straightforward way to do this would have been to linearly vary the output frequency. Shown below in an Arduino sketch:

// Use pin 9 as the PWM output
const int outputPin = 9;

void setup() {
  // Set the pin as a digital output
  pinMode(outputPin, OUTPUT);

void loop() {
  // Fade the brightness from 0 (min) to 255 (max) with 40ms delay per step
  for (int brightness = 0; brightness <= 255; brightness++) {
    analogWrite(outputPin, brightness);

However the light outputted by the LED does not scale linearly. If you were to use the very scientific metric of “Perceived Brightness” vs. time for the above sketch it would look something like the below for a linear PWM signal:


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Experiences with Buying Cheap Arduinos and shields on eBay

Recently I’ve started getting interested in electronics and in particular Arduino. Ardunios are a microcontroller boards that you can programme to perform actions. The board I am interested in is the entry level Ardunio Uno. This board has 14 digital inputs/outputs and 6 analogue inputs. The Arduino can be expanded with Shields, these are addon boards that stack on top of the Arduino to offer additional functionality (like ethernet, storage, motors etc.)

Buying genuine Arduinos in Ireland can be costly because they have to be ordered from suppliers in the US or UK/Europe. Often the cost of shipping and customs exceeds the cost of the Arduino itself!

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