Smart devices or a central portal: Simple single-purpose devices (SD devices) do their job, too

Advantages and disadvantages of simple vs. smart devices

The question whether it is better to use single-purpose devices or rather to integrate more functions into one device has been debated since the first microprocessors. By using more single-purpose devices, better system scalability can be achieved but possibly at higher costs. By integrating functions, hardware costs can be significantly reduced but there is an increased risk that a fault in one subsystem will make the whole system inoperable.

At the same time, the decision whether to use smart autonomous devices or a cloud-based solution should not be based on the device costs alone; it must reflect the actual application – for what purpose is an independent monitoring solution being implemented – as well as the system design and installation.

Smart devices (Poseidon, Damocles, PWR and so on)	SD-Devices
Autonomous operation without a permanent Internet connection	Easy installation by non-qualified personnel
Support for several types of communication protocols, easy integration into monitoring systems	Bidirectional communication works without the need for in-depth network knowledge
Internal logic can perform autonomous actions	Function easily changed using a unified portal
Extended support for M2M communication	Unified communication format
Internal datalog	Very stable operation
More complex system design	Higher system modularity
Installation requires expert personnel	System functionality limited by the portal capabilities
Higher price	Operation dependent on a third-party system

System design and scalability

Simple single-purpose devices offer a clear advantage. They contain a small, clearly-defined number of inputs, outputs and sensors. They do not combine functions within a single package; however, it is easy to combine different devices. This makes it much easier to design the entire ecosystem and also to extend it.

When designing a monitoring solution, it is important to keep in mind not just the function but also the range of monitored elements and quantities. Monitoring can encompass elementary quantities, such as temperature and humidity, and also things such as door contacts, equipment states, voltages or currents. From this point of view, single-purpose devices and smart devices serve equally well. In simpler applications, smart devices have an advantage because an all-in-one solution provides all the necessary elements and functions at low installation costs. So, to monitor the environment inside a rack, all that is needed is a STE2 with a thermometer, a humidity sensor and two door contacts, or a Poseidon2 3268 that can also control additional fans. However, in case of more complex applications, it is harder to keep the costs under control. Smart devices provide a limited number of inputs, outputs and sensors in various combinations; therefore, it is necessary to know all the available models and choose a suitable combination. It can easily happen that a user who needs just 1 additional digital input ends up purchasing an entire additional (and expensive) device.

Installation and configuration

Simple single-purpose devices are all configured at a single place – the central SensDesk portal.

Simple devices themselves do not process data in any way; they just send the data to a remote master system (the portal), where all further processing takes place. This requires highly reliable measurement devices and a robust method of registering them in the system; at the same time, it provides two significant advantages. All configuring and setting up is performed at a single place – in the central SensDesk portal. There is no need to configure each remote device separately, which might require creating tunnels through the Internet to each device. Anyone who has tried to make their data at home accessible over the Internet knows that setting up the required routing at the home gateway (e.g. modem) is not always a straightforward task. And while it is relatively easy to set this up for one device, it can become very complex for multiple devices. Simple single-purpose devices, such as SD-Devices or NB-devices, connect to the server automatically without the need to configure any tunnels.

Smart devices, by their nature, need to be installed by an expert who, in addition to the intended application, also understands computer networks, address translation, and so on. Such people are expensive to hire; moreover, they may not be always qualified and authorized to work on the equipment to be monitored. As a result, the installation may need two people – a technician installing the sensors and an engineer configuring the monitoring device. On top of that, if the installation is done at a customer’s premises, the customer’s IT department may need to be involved, too. If you need to monitor one rack, it is possible to fine-tune the settings and, with the help of the IT team, put in place remote access for possible reconfiguration. A large installation can use a virtual LAN (VLAN) to simplify the situation. However, in case of many devices at different physical locations, the situation becomes complex and the advantages of simple single-purpose devices quickly become an important factor.

Smart devices that allow connecting sensors and detectors to buses can save hardware costs but rigorous testing and documentation is needed. Without it, it will be very difficult to troubleshoot e.g. swapped sensors in full operation. Therefore, simple single-purpose devices make things much easier. These devices actively send data to the remote server; instructions for the installation crew can be as simple as “plug the brown sensor into jack 1 and the white sensor to jack 2”, minimizing the risk of errors.

In case of M2M communication, the communication port must always remain open on the target router / firewall, which requires the intervention of a network specialist.	Access to individual devices from the external network (Internet) is also uncomfortable with direct connections, as communication ports need to be open on the destination router / firewall (one port per device), which requires the intervention of a network specialist.
When SensDesk is used as an intermediary, there is a slight slowdown in communication, but there is no need to interfere with the network infrastructure, which increases the security of both the application and the rest of the network.	By using the portal solution for setting up the behavior, Saferange and other target application parameters, the security of not only the application but also of the rest of the network is again increased. This method is very user-friendly, and what is more important, it remains the same across different products.

Changing the device configuration

When it comes to reconfiguring the devices, the differences between simple and smart devices are similar as in the case of installation. The portal solution is simpler and faster to maintain. Moreover, a single experienced engineer can manage even very large systems.

M2M operation

When two devices need to cooperate, the solution must be chosen according to the particular application. Compared to all-in-one solutions, simple devices offer the advantage of easy scalability. However, a direct connection between two devices is always faster and more secure than an intermediate central portal. Due to the architecture of cloud solutions, when an action needs to be performed with an output of a device via the portal, it is necessary to wait until the device connects to the central server; this can take anywhere from tens of seconds to several minutes. On the contrary, Poseidon2 and Damocles2 devices can establish a direct connection between themselves and react within a few hundred milliseconds to a few seconds. However, if the devices are in different networks, such a connection requires special routing configuration; this may take significant effort or, in corporate networks, can be even impossible.

Suitable applications for smart devices

Smart devices, such as Poseidon2, Damocles2 or HWg-PWR, are ideal for use in critical applications where the reaction, such as the sending of a text message or switching an output, must be as fast as possible. These devices also keep track of the real time and maintain a time-stamped data log. Moreover, they support multiple communication protocols, such as SNMP, ModBus/TCP, MQTT and more; however, configuration is required for proper operation. They are, therefore, better suited for industrial applications or closed networks and systems.

Independence of the solution

The need for a truly independent monitoring is the strongest argument for using devices such as Poseidon2, Damocles2 or HWg-WLD (smart devices). These device can autonomously measure the monitored quantities, evaluate the measurements and, if needed, send alerts, turn on a back-up system or switch off the monitored equipment to prevent further damages. The only criterion here is the importance of the application and its purpose. To send e-mail alerts, all that is needed is a working connection to the Internet (a SMTP server); to send text messages, a HWg-SMS-GW3 in the same network can be used (some devices can also interface with a modem).

Any single-purpose device relying on cloud services or another server solution is dependent on Internet access. Such a topology introduces at least one element to the communication chain that the user does not have under control. For this reason, smart devices are better suited for critical applications, or for installations where a company policy prohibits the use of server-based or cloud services.

Suitable applications for single-purpose SD-Devices and NB-Devices

Simple single-purpose devices are primarily intended for larger installations in terms of their geographical scope or the number of sensors.
They are suitable for applications that encompass many small installations spread over multiple locations. They allow connecting a few sensors and detectors and thus enable simple installation. At the same time, they do not require any special configuration, apart from e.g. configuring the Wi-Fi in case of SD-Devices. All subsequent operations are performed in the SensDesk portal only, and can be done by a qualified person. The low per-device cost is an advantage when extending the system; it is sufficient to buy just the inputs or outputs that are needed.

NB-Devices are typically used at remote locations without electricity and internet.

Cooperation between smart and simple devices

Both technologies can be combined within a single solution. The SensDesk portal can be used as the unifying element for both monitoring solutions, combining their advantages. For example, smart devices can be used to measure values and simple devices to control remote outputs or watch for water leaks.