Input-, output-impedance and impedance matching

Input-, output-impedance and impedance matching

Impedances. You come across this property in various technical fields. Some examples are acoustics, optics, electrical circuits, to name a few.

Impedance is what the word says: the act to impede something. In case of wave propagation, this would be to impede propagation. This happens when a wave travels from one medium to another. In the case of an electrical circuit, impedance is the act to hinder a current in a circuit.

In this blog I will go a bit into this electrical impedance. And to be specific, impedances when connecting to circuits or devices. You deal with this whenever you electrically connect some output to an input. You can think of connecting your set of headphones to an amplifier or an audio-output of your notebook. But also for cable-tv when you are connecting the coaxial cable to the television set. Other, more technical, examples would be measuring voltages using an oscilloscope or simply connecting a sensor to a circuit.

In all these example it comes down to electrically connecting one thing to the other. We then deal with output and input circuits. Each of them have their own impedance. So what is the relation between them? Continue reading “Input-, output-impedance and impedance matching”


Buttons over touchscreens

Buttons over touchscreens

For years I tried getting used to it. And I still do not fancy them. Touchscreens. I have no choice to go along in this craze of technology using touchscreens for pretty much everything. I need my tactile feedback when I press a key. I need to know I have pressed a button. I need to know I am ‘on’ a key. Without it, I tend to make many mistakes typing on a touchscreen. A general feel of insecurity creeps up when using a touchscreen and it just doesn’t go away. “Did I press it? Did I not press it?”. And depending on the device there might be a lag between registering your touch and acting upon it. There are options to use haptic feedback. While this helps a bit, I still prefer to have physical feeling of touching a button before pressing. Continue reading “Buttons over touchscreens”

How to setup a low-power ATmega8 microcontroller

How to setup a low-power ATmega8 microcontroller

ATmegas are nifty little things. You can get them very cheap and they are very versatile to do simple things like controlling a LED, reading out a sensor, logging the data, controlling a display, etc.

For these simple applications the ATmega8 is usually sufficiently good. This chip only has 8 kB of flash data. But for small applications given above this is more than enough. For programs requiring more memory you can go for a higher numbered ATmega like the ATmega328.

Nowadays you can find ATmegas (usually the 328-kind) on Arduino boards. These require a certain voltage input of 5 – 12 V and are not necessarily power friendly. The required input voltage means that if you want to run it on batteries you have to combine it in such a way to obtain at least close to 5 V. This can be tricky if you want to build something compact and do not necessarily need a lot of power.

Figure 1: Typical use of an ATmega microcontroller. Sensors measure out the temperatures, relative humidity and the ambient pressure.

In this blog I will succinctly describe how to setup an ATmega8 at low power with the Arduino IDE. Also, I will describe the process of running the ATmega8 with only 2 AAA batteries or even a button cell. The process includes underclocking the ATmega8 from 16 MHz to 1 MHz using the internal oscillator. In the end this reduces power consumption considerably and allows the ATmega8 to run at lower voltages. Continue reading “How to setup a low-power ATmega8 microcontroller”

Physics of billiards: 90° rule

Physics of billiards: 90° rule

At first sight you would think it would be pretty easy to explain with physics why the balls move the way they move. Ideal case right? Spherical balls, all the same mass, bouncing off each other and bouncing off the side elastically…

Ofcourse, reality is a bit more complicated.

In this blog post I will show an easy case which is the 90 degree rule. This rule says that if the cue ball hits an object ball, the cue ball will deflect the object-ball’s trajectory by 90 degrees. Alright…, sketch time! Continue reading “Physics of billiards: 90° rule”

Arduino-controlled arcade stick mod (Part I)

Arduino-controlled arcade stick mod (Part I)

In this blog I will talk about the arcade stick mod I did for my HRAP2. I wanted to have programmed inputs for the arcade stick. Programmed inputs can allow for investigation of a (fighting) game engine. Although there may be many easier solutions for programmed inputs, I found it a fun project to use my Arduino for. A requirement I put myself is not to have the Arduino installed inside the arcade stick, so I could use the Arduino for other applications as well. In order to let the Arduino control the inputs for the arcade stick, the inputs had to be wired to the Arduino digital outputs. This meant using a wire from the PCB to the Arduino digital output.

As this is a Playstation 2 arcade stick, the first thing I needed to do was gut out the PCBs.

These guts were previously used as PCBs for the PS2 and PS3. Well, I don’t need them no more. And I planned to install the Brook Universal Fighting Board, which supports Xbox One, Xbox 360, PS4, PS3, Wii U, PC and Switch all in one go! This means using the same controller for different consoles :). Continue reading “Arduino-controlled arcade stick mod (Part I)”

Lengte van dag en nacht

Waarom gaat de zon eerder of later onder voor een andere plek op aarde? Ofwel, waarom verschilt de lengte van de dag of nacht voor verschillende posities op aarde?

Wat we uit ervaring weten is dat in Nederland de dagen korter zijn in de winter en langer in de zomer. Wat we misschien ook wel weten is dat de zon in de tropen min of meer altijd rond hetzelfde tijdstip onder gaat. Maar waarom is dat zo?
Een kort antwoord is dat dit komt door

  • de axiale tilt van de aarde,
  • de positie van de aarde ten op zichte van de zon.

En omdat de aarde roteert om zijn as, zorgt dit voor de dag-nacht cyclus.

In de bovenstaande figuur zien we enerzijds dat de aarde roteert zonder een axiale tilt en anderzijds met tilt. Dit opzich zeg niet zoveel als er niet aangegeven is relatief tot wat deze hoek is (immers je hoofd draaien geeft hetzelfde effect), maar is meer om een gevoel te geven hoe de aarde roteert om zijn as bij een tilt. De tilt is gegeven relatief tot de orbitale as van de aarde om de zon. Deze hoek wordt ook wel obliquity (engels) genoemd. Continue reading “Lengte van dag en nacht”

Hypotheekrenteaftrek, Wet Hillen

Je ziet de termen allemaal voorbijkomen. Hypotheekrenteaftrek, de Wet Hillen. In deze blogpost probeer ik het met een voorbeeld kort uiteen te zetten.

Stel je hebt een inkomen van 50 000 euro. Hierover moet je belasting betalen. In Nederland hebben we een aantal belastingschijven. In dit geval (as of 2017) val je in de schijf dat 40.80% loonbelasting moet betalen. Ofwel

  • Inkomen: € 50 000
  • Belasting: 0.4080 \times  € 50 000 =  € 20 400

Hypotheekrenteaftrek is de hoeveelheid rente dat je betaald in een jaar aan je hypotheek dat je van je jaarlijkse inkomen mag aftrekken. Wat betekent dit? Stel je hebt een hypotheek van 200 000 euro en je betaalt daar 2% rente over. Continue reading “Hypotheekrenteaftrek, Wet Hillen”