Do-it-yourself construction kits for sensor stations is a novel approach for citizen driven sensor networks. In this paper we present the development of SenseBox, a toolkit for open source sensor applications. We provide manuals and open source toolkits for hardware makers to establish a large scale sensor network in Germany, and additionally for schools to teach secondary school students programming in a playful and simple way based on open source microcontrollers. All collected data is open and being published on OpenSenseMap, our platform for open sensor data. After a test phase where we equipped citizens with construction kits for continuous measurements we discovered that most of the stations were disconnected after a few weeks. Following from that we performed a user study to reveal possible error sources during the wiring process, software installation and online registration on OpenSenseMap. Missing general computer skills led to larger problems than wiring of hardware parts.