HP 300s+ Scientific Calculator – Short Review

HP 300s+

HP 300s+

A few weeks ago I was searching for a new calculator which could do hexadecimal conversions as I often need them while programming and I find it more convenient to have a dedicated calculator on my desk instead of using a software calculator on the PC. In school I had a TI-36X solar from Texas Instruments, which could do this easily and now I wanted to have an additional calculator with similar features.

While searching for alternatives I found the HP 300s+ Scientific Calculator. We also used to have several calculators from HP which I also very liked. It looked like a decent entry-level calculator which is advertised with a “Perform decimal and hexadecimal conversions.” feature. For 15€ including shipping directly from HP it looked like a bargain. It was delivered very quickly by UPS. Continue reading

Maker Faire Hannover 2013

Heute hat die erste Maker Faire Hannover statt gefunden. Dieses Event konnte ich mir natürlich nicht entgehen lassen! Ich hatte sogar etwas Glück und habe bei @reichelt_el Eintrittskarten gewonnen. Pünktlich um kurz nach 10 Uhr war ich am Hannover Congress Centrum und der Andrang war (für mich) überraschender Weise schon sehr groß. Die Maker Faire bestand aus einer Halle mit zahlreichen Makern die ihre Projekte vorstellen, vielen Hackerspaces aus ganz Deutschland und ein paar Sponsoren. In zwei Veranstaltungsräumen gab es Vorträge. Im Außenbereich gab es außer Workshops und weiteren Ständen von Makern auch etwas zu Essen und zu Trinken. Continue reading

My first iOS app – hue⁺

When I first heard of Philips hue I really liked the idea of controllable LED bulbs. I googled a little bit to understand how it works and finally found out the it is based on ZigBee Light Link. So I had the idea to buy one of these starter kits and build some AVR based controller for them on which I wanted to implement the protocol myself. On the embedded world 2013 in Nürnberg I even found some non-Philips stuff from Dresden Elektronik that was compatible to ZigBee Light Link. So I bought a ZigBee Sniffer from Dresden Elektronik and some XBee ZB modules and was ready to start. Continue reading

Non-uniform distributed random numbers

Creating non-uniform distrubed random numbers is not straightforward. Usally programming languages like C provide functions like rand() which returns an integer random number between 0 and RAND_MAX or drand48() with returns a double random number between 0 and 1. The numbers returned by these functions are uniform distributed meaning that if you run them very often you get each number by the same amount.
If you want random numbers in other ranges, these can be rescaled easily. For example, if you need integer random numbers between 1 and 10 you simply could get a random number x from rand() and apply the function \(f(x) = 1 + 9 \cdot x\) to it.

But what if you want to distribute them in a non-uniform way? Continue reading

Webfont rendering on different browsers/platforms

Yesterday, I updated my blog to use webfonts. As I was curious how they look on different platforms in different browsers I made some comparisons. I tried to cover all major browsers on various operation systems. As a rendering example I took my blog post about AirPlay Simultaneity as it uses three different fonts within the first paragraph.

For each browser/platform combination I made an image consisting of an overview of the rendering and a detail view. On the left side of each picture you can see a simple screenshot which is displayed in such way that it is scaled by one over device-pixel-ratio. That means, that all PC screenshots are displayed 1:1, where as the iPad 3 screenshot is display at 50 % and the Nexus 7 at 75 %. On the right side is a zoomed view of a few characters of each font used. It is displayed with a magnification factor of 4 for the mobile devices and 5 for the PC devices. Continue reading