In a Gerber viewer, the layers seem to be empty,

Ah.  ALWAYS check your gerbers before sending off a design...

Yeah ... Luckily, it was not important for either of the projects. Still, for the next one I really would like to know what I did wrong.

@pwillard
That's another possibility. Looks fine. But again, it is only 10$ for 10 boards, and I do not have SMD headers at hand.

Yes, I had both the adapter and another project (board for a Nexus 7 docking station using the loading pins) made at Seeedstudio. Worked very well, took around 4 weeks and the quality is fine.
I did the design in KiCAD and indeed I could use some feedback: Both my orders came without solder masks. In a Gerber viewer, the layers seem to be empty, despite the fact that I think I added them in KiCAD. So, I would appreciate if you or someone else could point me to my error.

I added both project, in case someone is interested.
Known issues of the Nexus board:
- Components would be better placed on the other side, as they now are positioned on the side where the Nexus will dock
- Holes for resistors etc. are only 2,54mm apart, so regular components will not fit very well. Should be replaced with SMD components or moved apart. For us, this was no problem, as we do not use the audio part and just put the circuits in for completeness
- Board could use some holes for screws.

Thanks ... ok, I'll just add a voltage devider.

I know there are other displays, but those come at nearly two times the cost. For abstraction, the Adafruit Library works very well for my purpose. Don't see any problem there.

This one:
http://www.ebay.de/itm/Error?errid=5&item=251110441587pt=Bauteile&var=550175401939&hash=item3a797823c2

I removed two resistors in the back to make it work via SPI. It does work with 5V when testing, but I am not sure it won't reduce the lifetime.

Just a quick question: what voltage rnge can I apply to digital input for HIGH on a 5V or a 3.3V Arduino? I would like to use a RTC using 5V and a OLED display using 3.3V
If the RTC takes 3.3V as HIGH and the microcontroller@3.3V takes 5V as HIGH without problems, I needn't use a logic level shifter ...

Just connect alll 5V pins to the 5V pin of your Arduino.
You can do it like this

5V---o---o---o

or like this

5V-----
   |   |   |
   o   o   o

or like this

5V--o
||---o
|----o

It is the same electrically (ideally, but that doesn't matter here). Same for ground.

Yes, I could solder it on one side, but it wouldn't look that nice. I have jumper wires, but I would like to have it fixed on the breadboard, not lying around on a cable.
As far as I understand, I would get 10 PCB for 10$ (+ shipping, making it about 10€) from Seeedstudio. So cost is not an issue, neither is a bit soldering.
Apart from that, I am really interested how the order comes out. I would just appreciate if someone would confirm that my layout is technically correct, as I have no background with PCBs.

I have build up some stuff on breadboards by now, but often I have trouble with double row pin headers. So I decided to make an adapter as my first PCB design. Simple thing, a double row pin header on one side (female for direct access or male for ribbon cable), and two on the other side, far enough apart to fit across the middle gap of a common breadboard.
Sideview:

Code:

_||_
|  |

As I have to solder on both sides, I need it to be plated-through, so i'll have to have it manufactured. Seeedstudio seems to be a very cheap possibility for a small batch.
I attached my KiCAD project. As this is my first try, could anyone have a look and tell me if this will result in what I want? The 3D image from KiCAD looks right, but I can't make out the drilling holes in the board layout, for example.

Why don't you use a digital sensor, like DS18B20?

Oh dammit. I put the µC and the display together some time ago and now I just assumed it also works with SPI - so I just wired everything like two SPI devices.
 Obviously, it does not. So, that explains alot.

Thanks!

Strange. I mean, it's pastebin. Pretty standard ...

Code:

// -----------------------------------------------------------------

#include <OneWire.h>
#include <DallasTemperature.h>
#include <SPI.h>
#include <SD.h>
 
// Data wire is plugged into pin 7 on the Arduino
#define ONE_WIRE_BUS 7
 
// Setup a oneWire instance to communicate with any OneWire devices
// (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);
 
// Pass our oneWire reference to Dallas Temperature.
DallasTemperature sensors(&oneWire);
float temperature = 0.0;

// -----------------------------------------------------------------

#include <LiquidCrystal.h>

// Connections:
// rs (LCD pin 4) to Arduino pin 12
// rw (LCD pin 5) to Arduino pin 11
// enable (LCD pin 6) to Arduino pin 10
// LCD pin 15 to Arduino pin 13
// LCD pins d4, d5, d6, d7 to Arduino pins 5, 4, 3, 2
LiquidCrystal lcd(12, 11, 10, 5, 4, 3, 2);

int backLight = 13;    // pin 13 will control the backlight

// -----------------------------------------------------------------

//SD card
const int sdPin = 9;
File logFile;

// -----------------------------------------------------------------

void setup(void)
{
  // start serial port
  Serial.begin(9600);
  Serial.println("Dallas Temperature IC Control");
  // Start up the library
  sensors.begin();
 
  pinMode(backLight, OUTPUT);
  digitalWrite(backLight, HIGH); // turn backlight on. Replace 'HIGH' with 'LOW' to turn it off.
  lcd.begin(16,2);              // columns, rows.  use 16,2 for a 16x2 LCD, etc.
  lcd.clear();                  // start with a blank screen
  lcd.setCursor(0,0);           // set cursor to column 0, row 0 (the first row)
  lcd.print("Dallas Temperature IC Control");    // change this text to whatever you like. keep it clean.
  lcd.setCursor(0,1);           // set cursor to column 0, row 1
  lcd.print("DS18B20");
  delay(1000);
 
  if(!SD.begin(sdPin)) {
    Serial.println("Failed to initialize SD card");
//    lcd.setCursor(0,0);
//    lcd.println("Init SD failed  ");
  } else {
    Serial.println("SD initialized.");
//    lcd.setCursor(0,0);
//    lcd.println("Init SD success ");
  }
  delay(1000);
}
 
 
void loop(void)
{
  // call sensors.requestTemperatures() to issue a global temperature
  // request to all devices on the bus
  Serial.print(" Requesting temperatures...");
  sensors.requestTemperatures(); // Send the command to get temperatures
  Serial.println("DONE");
  temperature = sensors.getTempCByIndex(0);

  Serial.print("Temperature for Device 1 is: ");
  Serial.println(temperature); // Why "byIndex"?
    // You can have more than one IC on the same bus.
    // 0 refers to the first IC on the wire
  lcd.setCursor(0,0);
  lcd.print(temperature);
  lcd.print("*C         ");
  lcd.setCursor(0,1);
  lcd.print(millis()/1000);
  lcd.print(" sec                 ");
 
  logFile = SD.open("cookLog.txt", FILE_WRITE);
  logFile.print(millis());
  logFile.print("\t");
  logFile.println(temperature);
  logFile.close();
}

Hi,

I am trying to log and display temperatures. I have a Duemilanove on a breadboard
with this SD card module http://www.ebay.de/itm/Neu-SD-Memory-Card-Module-Slot-Socket-SPI-Reader-For-Arduino-ARM-MCU-3-3V-5V-/261073492935?pt=Wissenschaftliche_Ger%C3%A4te&hash=item3cc9315bc7
and this display http://www.ebay.de/itm/5pcs-New-5v-1602-LCD-Display-Module-Blue-for-Arduino-2560-UNO-R3-ARV-STM32-ARM-/280928964351?pt=Bauteile&hash=item4168abceff

Now, the logging works. Always. The LCD, however, stops working as soon as as SD.begin is called and holds the last text displayed. Without line 59-67, the display works fine again (but of course, the logging does not). So, the wireing seems to be ok. I don't know where to start searching the problem ...

Code can be seen at http://pastebin.com/e7e4ASdU

Sure, if you need more voltage, than you should input more voltage
I am not powering anything above 5V and 5V-MicroUSB becomes widely available, so I think that is the way to go for me. Before I am having the PCB made I will test a bit on the breadboard, complete the software and then I will present the project and ask for specific comments

I am not going to use a ready-made Arduino board, so my question was: Build a DC-Input e.g. 7-12V with a 7805 regulator or similar, or go with a MicroUSB port and some external 5V power source? This thread seems to suggest the latter.

Ok, so there really seems to be not more reason then "giving addition supoport for more and lesser quality power support".
Seems to me that for my first project, I can directly go with 5V input.