is it possible to connect the Gertbot with a Windows PC using a USB-to-Serial-converter. Or is the Voltage (5V) to much for the uart interface on the gertbot?
I don't want to damage the gertbot.
A USB-to-Serial-converter is exactly what I am using in the demo (http://youtu.be/qnr7AlwMDPc)
There are several different types, 5V signals and 3v3 signals. You need to buy the 3V3 version. Both types output 5V on the (red) supply wire.
I even have run two Gertbots from one USB cable although according to the manufacturer it could only supply enough current for one.