Where do the relays get the 12V they need?

This is a source of confusion for a lot of people. The Relays are 12V but an arduino puts out 5v.

Am I supposed to feed the arduino 12V and let the I/O Shield take this from the Vin pin?

Correct, Arduino needs to be supplied 12VDC.
Running it from a USB port will not drive the relays.

What is the power consumption of the board?
I use the ka05 on top of an Arduino UNO in combination with the Dragino shield.

The Dragino shield is powered through the 5V circuit of the UNO and Dragino advises to use maximum 7V DC input to avoid overheating the Voltage regulator on the Arduino UNO board. Adding the KA05 not only requires the higher input power, but also increases the load on the 5V circuit too.

At first I wanted to use the KA05 in combination with the Arduino Yun (which I have too), but apparently the YUN requires the KA08 which can’t be ordered now.

Would this solution be ok:

  • Power the Arduino/Dragino combi through the USB with 5V
  • Power the KA05 by disconnecting the KA05 Vin pin from the arduino and by putting 12VDC between GND en Vin on the KA0

Sorry, board power consumption is not documented.
Anyway, 5V power consumtion can be ignored, since it is only a control voltage.
Most likely, powering the KA05 from an external 12VDC source is the best solution.