[en] In this work we propose to monitor in real time the storage conditions of the cargo transported in the hold of a ship, using low-cost free software and hardware that has a great potential for scalability (increasing the number of sensors connected to the same server) without too many added costs. For this purpose, an electronic data acquisition system (DAES) called MRCAB (remote monitoring of environmental conditions in the hold) has been designed. With this system we will be able to obtain records of different environmental variables (such as pressure, temperature, humidity, etc.) of all the holds of a ship, in real time, from any point on the planet (with an Internet connection). This project is part of the so-called "Internet of Things" or IoT, where a large number of devices establish communication between them through one or more protocols that allow the exchange of information (through messages). In this project, new forms of M2M (machine to machine) communication are used to transmit and store sensor data, leaving behind asynchronous serial transmission protocols such as RS232, RS422 or RS485, which are still the most commonly used for this type of installation. The protocol that we will use to transmit the data recorded by the sensors is the MQTT (MQ Telemetry Transport) communications protocol, which is one of the most widely used protocols in IoT projects. This is a messaging protocol based on publication-subscription that works over the TCP/IP protocol and that allows us to connect multiple sensors at the same time, overcoming the difficulties of previous communication systems and simplifying the connection systems between the sensor and the unit receiving the data. The information obtained by the sensors will be stored in a InfluxDB database, and a Grafana web application will be deployed and configured to allow users to visualise the data collected in different graphs, allowing them to configure the time interval from which the data will be displayed, as well as to configure alerts to notify the user in case any condition is met. With the implementation of this DAES on any ship, the objective is not to replace the existing systems for recording environmental variables but to complement them and thus optimise the unloading processes, give confidence to the recipient of the cargo and the shipowner, simplify the documentation to be presented by the crew at the time of delivery, and in general to add value to the choice of a ship with this system for a given freight.

[gl] Neste traballo proponse monitorizar en tempo real as condicións de almacenaxe da carga transportada na bodega dun buque, utilizando software e hardware libre de custo reducido que dispón dun gran potencial de escalabilidade (aumentar o número de sensores dependentes dun mesmo servidor) sen demasiados custos engadidos. Para isto, deseñouse un sistema electrónico de adquisición de datos (SEAD) denominado MRCAB (monitorización remota das condicións ambientais na bodega) co que poderiamos ter rexistros de diferentes variables ambientais (como presión, temperatura, humidade, etc.) de todas as bodegas dun barco, en tempo real, dende calquera punto do planeta (que dispoña de conexión a Internet). Este proxecto está enmarcado dentro do chamado "Internet das cousas" ou IoT onde unha grande cantidade de dispositivos establecen comunicación entre eles a través dun ou varios protocolos que permiten o intercambio de información (a través de mensaxes). Neste proxecto úsanse novas formas de comunicación M2M (machine to machine), para transmitir e almacenar datos de sensores e deixárense atrás protocolos de transmisión serie asíncrona como o RS232, RS422 ou RS485 que seguen a ser os mais utilizados para este tipo de instalacións. O protocolo que usaremos para transmitir os datos rexistrados polos sensores é o protocolo de comunicacións MQTT (MQ Telemetry Transport), o cal é un dos protocolos máis usados en proxectos IoT. Este é un protocolo de mensaxería baseado en publicación-subscrición que funciona sobre o protocolo TCP/IP e que nos permitira conectar múltiples sensores ó mesmo tempo superando as dificultades de sistemas de comunicación anteriores e simplificando os sistemas de conexión entre sensor e unidade receptora de datos. A información obtida polos sensores almacenarase na base de datos InfluxDB, e despregarase e configurarase unha aplicación web Grafana que permitirá que os usuarios poidan visualizar os datos recollidos en diferentes gráficas, permitindo configurar o intervalo de tempo do que se amosarán os datos así coma configurar alertas que notifiquen ó usuario no caso de que se cumpra algunha condición. Coa implementación deste SEAD en calquera buque, non se persigue substituír os sistemas de rexistros de variables ambientais existentes pero si complementalos e con iso optimizar os procesos de descarga, dar confianza o destinatario da carga e ó dono do buque, simplificar a documentación a presentar pola tripulación no momento da entrega, e por en valor a elección dun buque con este sistema para un determinado flete.