This thesis describes the development of a load weight device and emergency phone system, both used in domestic elevators. The purpose of the load weight device is to prevent car movement in case of an overload, which exceeds 10 % of the maximal permitted load. The purpose of the emergency phone is to call a rescue service in the event of an elevator malfunction, even when the power is lost.
We begin the development of the load weight device on the basis of functional demands, which are described in European standard EN81-1 in addition to other functions, which are needed to provide greater comfort in elevators. We begin the development of the emergency phone system on the basis of functional demands, which are described in European standard EN81-1 [14] in addition to the European telecommunications standard TBR21 [13]. First, the thesis introduces different elevator cabin load measurements, followed by the theory of load cell with strain gauge, used hardware and software development. This is followed by electronic board design for emergency phone system, used integrated circuits and software design, which will result in a user friendly interface. At the end sometest results for both devices are presented.
The final result are two devices. The first is a load weight device, which uses a load cell designed to be installed on the steel ropes of an elevator in order to measure the load inside the cabin. The load is measured as the strain gauge deforms, causing the output voltage to change. When this voltage change is processed, relays switch ON or OFF. The second device is a hands free emergency phone system with the ability to record and play messages with parasitic power supply using an analog phone line.
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