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Technology Evaluation

This section of the documentation is about the technology evaluation of the software we used and partly tested. After a short explanation, we highlight the advantages and disadvantages of the respective software. We then briefly summarise these in a conclusion and supplement this with a personal opinion and experiences. Each sub-page deals with a separate topic.


In addition to the subpages, we evaluate the software used in a clear table.

Service Technology Installation Configuration Usability Error rate Documentation
Speech to Text DeepSpeech Hard without experience* Easy Medium High Good
LED Control Hermes LED Control Medium Easy Good None Medium
Text to Speech Mozilla TTS Hard Easy Bad Medium Medium
Text to Speech Nano TTS Easy Easy (in Rhasspy) Good None Bad
Intent Handling Node-RED Easy Easy Medium Low Good
Wake Word Raven Easy Easy (in Rhasspy) Good Low Good
Set of voice assistant services Rhasspy Easy Easy Medium None Good
Microphone ReSpeaker Medium None Good None Good
Intent Recognition Snips-NLU Hard without experience Medium Good Low Good
MQTT broker Mosquitto Easy Easy Good None Good
Single Board Computer Raspberry Pi Easy None Good None Good
Operating System Raspbian Easy Medium Good Medium Good
Zigbee Adapter CC2531 Easy None Good None Medium
Zigbee Adapter ConBee2 Easy None Good None Good
Bridge from Zigbee to MQTT Zigbee2MQTT Easy Medium Medium None Good

*as for German pretrained model

Statement for disability and educational assistance

The system is only suitable for use in the disability and educational assistance, if none of the operators has a strong speech accent or a speech impediment, otherwise the spoken sentences will not be recognized correctly with DeepSpeech. If this is not the case, it can be used to control Zigbee devices very well. This is also very practical for the handicapped or for educational aids who do not have a free arm to switch on the light or to lower the shutters. With NodeRED you can also easily automate daily sequences so that you don’t have to do them every time. Problems could arise, however, if children like to turn lights on and off, by voice this is much easier than with normal light switches. Normal light switches may be more difficult for children to reach. The Rhasspy system is a very robust system that runs without further maintenance without any problems, it does not crash and does not need internet for the simple skills (time, access to Zigbee sensors and actuators). Even if you pull the plug, the system does not get destroyed. This must then only be plugged in and after a few minutes, the voice assistant works again.

Most importantly, the Rhasspy voice assistant is privacy compliant, unlike Google Assistant and Alexa. Rhasspy works completely autonomously without sending voice files or private data to the Internet, as mentioned above, it also works without an Internet connection.

Software/Hardware overview

In the following component diagram, all the technologies listed above have been brought together in relation.

Software and hardware overview

Table of contents