Apr 062014

Topic: This project is about making photos of a sunset with a Nikon D200. Starting with full daylight photos will be taken until astronomical sunset (sun is at -18 degrees below horizon).

This requires constant adaptation of the cameras settings (ISO / aperture and time) due to the diminishing light.

I will record the luminosity with the Arduino, so I can set the average brightness of the single images afterwards accordingly.

For this I bought several luminosity sensors from Watterott:

  • Sparkfun Weather Shield
  • TSL2561 light sensor (digital) (0.1 to 40,000 Lux)
  • TSL45315 light sensor Breakout (3 Lux bis 220k Lux)
  • CoreLight (0.015 lux to 64,000 lux)

I will try which one is the best, measure some sunsets and gauge the camera against it.

In order to better understand what I am doing, I am developing some small tool, which tells me some astronomical data – as the position of the sun by time and date and some star positions.

For this I will look for a better tool than Excel and VBA… :)


First I downloaded a data base of star positions:

And an OpenGL-Sample containing the pattern of the earth:


A website containing C-code for positions of planets, the moon and the sun (based on the book “Astronomie mit dem Personal Computer” von Oliver Montenbruck und Thomas Pfleger):

Using the TSL2561 light sensor:

Using the TSL45315 light sensor:

Using the CoreLight light sensor:

  • Connect as follows:


Picture 1 of 1

 Posted by at 8:43 pm
Nov 242013

Topic: How to scan color transparencies.


I bought an old Heidelberg Linoscan 1450 scanner together with VueScan and would like to scan my 4×5″ negatives/slides. There are several problems to solve:

1. The scanner has some bad pixels, so I get stripes in the scanned image (solved by downloading and installing the newest version and clicking on “calibrate”).

2. How to get rid of newton rings?


I started with a dry scan and asked myself what side should be up: The base or the emulsion?

The first thing I noted was that the film bends. According to my observation it bends the edges upwards, when the emulsion side is up. Since I don’t have a film holder, I put the emulsion side down. This enables me to fix the film with tesa film on the scanner, where the tesa touches only the base side. This apparently solved already the Newton ring problem – at least for some photos. There were still some showing up newton rings.

So I tried a wet scan: With a normal spray bottle I sprayed some water on the glass surface of the scanner and placed the slide (emulsion side up = not touching the water) on the scanner. I tried to remove all air bubbles under the film, but was quite unsuccessful as I saw on the scan. Next try will be wo put the emulsion side down and use a roller (from linol-cutting) to squeeze out the bubbles. But for that I should buy a clean one first… :)

My overall impression comparing the dry scan with the wet scan was, that there is only a very slight improvement of the sharpness in the wet scan. If the water is applied to the upper side (base), it had some effect on the color of the image: the scan comes out darker in comparison with the dry scan.

After washing the image, it dried normally having no visible effect on the color nor leaving some marks behind.




 Posted by at 3:48 pm
Nov 162013

Topic: This post is about the application of the MF522-AN RFID reader and the Arduino for cards-magic (current stage: Proof-of-concept).


Effect: A randomly picked spectator shuffles a deck of cards, picks out a card of his choice and puts it into an envelope, which he places on a table. The magician is able to tell which card he has chosen, just by concentration – never having touched the card not the deck.



Getting the MF522-AN RFID reader working was pretty straightforward based on a script by Dr.Leong (, which was sent to me after I purchased the hardware at ebay.


Pin on RFID reader Meaning Connect with Arduino Colour of the cable on the   photo
8 SS Pin 10 Yellow
7 SCK Pin 13 Orange
6 MOSI Pin 11 Green
5 MISO Pin 12 Blue
4 Nothing
3 M-GND Grnd Black
2 RST Pin 5 White
1 M+3.3V 3.3V Red


Wiring the MF522-AN RFID reader with the Arduino

Picture 1 of 2


In order to place a RFID chip into every card, I had to find rather thin ones (not built in plastic), which I found at ebay:

“NFC tag sticker label RFID IC 13.56MHz ISO14443A Mifare1k S50 Compatible” sold by zillashop:


I then placed the RFID chip between two cards, glued them together (see photo 2). The RFID reader was able to read out the chip through my working desk: I placed the Arduino with the RFID under the desk and placed the envelope above it (on the desk).


I modified the script by Dr. Leong such that it would print the cards name (in case the RFID tag was known, otherwise it would use the standard output of Dr. Leong (as the Chinese characters will not show up here, I deleted the comments).

/* Arduino-program: I will only quote the modified "loop" statement here */
void loop() {
   uchar i,tmp;
   uchar status;
   uchar str[MAX_LEN];
   uchar RC_size;
   uchar blockAddr;
   String mynum = "";
   status = MFRC522_Request(PICC_REQIDL, str);
   if (status == MI_OK) {
      Serial.println("Card detected");
      Serial.print(" , ");
      Serial.println(" ");
   status = MFRC522_Anticoll(str);
   memcpy(serNum, str, 5);
   if (status == MI_OK){
      char* cardName=new char[200];
      cardName = "";
      if (serNum[0]==75) cardName = "Ace of diamonds";
      if (serNum[0]==219) cardName = "Ace of hearts";
      if (serNum[0]==43) cardName = "Ace of spades";
      if (serNum[0]==59) cardName = "Ace of clubs";
      if (serNum[0]==235) cardName = "Queen of hearts";
      if (cardName=="") {
          Serial.println("Unknown card! The card's number is : ");
          Serial.print(" , ");
          Serial.print(" , ");
          Serial.print(" , ");
          Serial.print(" , ");
          Serial.println(" ");
      } else {
   //Serial.println(" ");


In order to do something with the output I wrote a small processing script to run on my PC, which had the Arduino attached to it. This is definitely why its currently only a “proof of concept”. In the final stage I will have to find a different method to transfer the information to the magician :)…

I used a modified code from D. Shiffman ( Unfortunately it took me quite some time to get it running, as some class definitions were missing and I needed to download the javax.mail first. I found the solution here:


import processing.serial.*; 
import javax.mail.*; 
import javax.mail.internet.*; 
import java.util.Properties;

final int LINE_FEED = 10;
Serial arduinoPort;

import javax.mail.Authenticator; 
import javax.mail.PasswordAuthentication;

public class Auth extends Authenticator {
  public Auth() {     super();   }
  public PasswordAuthentication getPasswordAuthentication() {
     String username, password;
     //System.out.println("authenticating. . ");
     return new PasswordAuthentication(username, password);

void setup() {
   String arduinoPortName = Serial.list()[2];
   arduinoPort = new Serial(this, arduinoPortName, 9600);

void draw() {
   if (arduinoPort.available() > 0) {
     final String arduinoOutput = arduinoPort.readStringUntil(LINE_FEED);

             // Create a session
       String host="";
       Properties props=new Properties();
             // SMTP Session
       props.put("mail.transport.protocol", "smtp");
       props.put("", host);
       props.put("mail.smtp.port", "25");
       props.put("mail.smtp.auth", "true");
             // We need TTLS, which gmail requires

             // Create a session
       Session session = Session.getDefaultInstance(props, new Auth());
       try       {
             // Make a new message
         MimeMessage message = new MimeMessage(session);
             // Who is this message from
         message.setFrom(new InternetAddress("<INSERT YOUR EMAIL USERNAME HERE>", "<INSERT YOUR EMAIL USERNAME HERE>"));
             // Who is this message to (we could do fancier things like make a list or add CC's)
         message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("<INSERT TARGET EMAIL ADRESS HERE>", false));
             // Subject and body
             // We can do more here, set the date, the headers, etc.
         println("Mail sent!");
       catch(Exception e)       {


Putting it all together it resulted in an e-mail to my iPad with subject (and body) being the name of the card, which was in the envelope put on my desk under which I put the RFID unit (wired to the Arduino, which was on USB cable attached to my desktop PC)…  :)



 Posted by at 1:17 pm
Oct 052013

Topic: In order to display the measured voltage values graphically, the data need to be transferred to the computer.


Sample for measuring the light intensity

Picture 1 of 1


The Arduino sketch:

In order to transmit the data as quickly as possible (for having a good time resolution of the measurements),

the Arduino sketch has to be reduced to a minimum. All the evaluations are done on the main computer.

/* Measures and transmits the Voltage to the external computer. */
// the setup routine runs once when you press reset: 
void setup() {     
    // initialize serial communication at maximum 115200 bits per second:     

// the loop routine runs over and over again forever: 
void loop() {       
    /* Read the voltage over the photo sensistive resistor */     
    int sensorValue = analogRead(A0);     
    Serial.print("I: ");     

 The Processing sketch on the main computer.

This is a modified sketch of a sketch written by Maik Schmidt.

import processing.serial.*;

final int WIDTH = 1000; 
final int HEIGHT = 600; 
final int xCenter = WIDTH / 2; 
final int yCenter = HEIGHT / 2; 
final int LINE_FEED = 10;

Serial arduinoPort; 
int time = 0; 
float voltage = 0;

void setup() {   
   size(WIDTH, HEIGHT);
   String arduinoPortName = Serial.list()[2]; // modify this according to your system environment
   println("Arduino is at : "+arduinoPortName);
   arduinoPort = new Serial(this, arduinoPortName, 115200);

void serialEvent(Serial port) {
   voltage = getSensorData();
   if (voltage != 0) {
     println("Voltage: " + voltage);

float getSensorData() {
   if (arduinoPort.available() > 0) {
     final String arduinoOutput = arduinoPort.readStringUntil(LINE_FEED);
     int result = parseArduinoOutput(arduinoOutput);
     return result * (5.0 / 1023.0);
   } else {      
      return 0;   

int parseArduinoOutput(final String arduinoOutput) {
   int number = 0;
   if (arduinoOutput != null) {
     final int[] data = int(split(trim(arduinoOutput), ' '));
     //print("Data length "); println(data.length);
     if (data.length == 2) {
       number = data[1]; // Integer.parseInt(data[1]);
   } else {
      number = 0;
   return number; 

void init_screen() {

void draw() {
    int yValue;   
    point(time, yValue);
    if (++time == WIDTH) {
       init_screen(); time = 0;
 Posted by at 5:15 pm
Sep 102013

Topic: How to install a browser that allows practically anonymous browsing in the web.

Search for “TOR Browser” and read the manual.

(The computer magazine “chip” has a free TOR browser package).

 Posted by at 10:50 pm