The sensor itself
To recognize obstacles in the near surrounding I choose the ultrasonic sensor HC-SR04. This sensor has a good support for Arduino and is also very cheap. The basic technical specifications are the following
The sensor case
Next, I was searching for a suitable casing for my HC-SR04 ultrasonic sensor to mount it on my robot base. On Thingiverse you will find a perfect component which meets the basic requirements: adjustable and easy to mount. You only need two little screws to mount it onto the SZDoit T200.
Here the link to the mentioned part on Thingiverse: HC-SR04 Casing + Angle Adjustable Cradle.
All related and needed files can also be found in the project repository on GitHub: