• • • SURGE + CIRCUIT PROTECTION • • • The expanding need for circuit
protection in mission-critical IoT devices By Ian Doyle, director sales & marketing EMEA, ProTek Devices
T
he Internet of Things (IoT) market is projected to grow from USD 714.48 billion in 2024 to USD 4,062.34 billion by 2032, according to
Fortune Business Insights. It is anticipated that IoT in agriculture will grow amongst the fastest. This is due to the budding demand for field-based equipment and sensors. But this growth also brings unprecedented challenges that require thinking in new ways to meet mission-critical design requirements. Delivering successful IoT means overcoming IoT’s 5Cs of technical challenges: connectivity, continuity, coexistence, cybersecurity and compliance. As a result, device circuit protection has become mission critical.
supply lines or induced onto communication signal lines. According to the Insurance Institute for Business and Home Safety, industry experts estimate that power surges cost businesses lost time, equipment repairs and replacements, totalling $26 billion annually.
The IEC 61000-4-2 ESD Standard The International Electro-Technical Commission (IEC) has defined the Human Body Model (HBM) for an ESD event. The intent is to guide system designers in implementing adequate overvoltage protection in their applications. The Commission defined the HBM ESD discharge impulse, with four levels in 61000-4-2 standard. The impulse waveform has a rise time of less than 1 ns and decay time of 60 ns, as shown in Figure 3.
Figure 2: Example of Electrical Transient Damage to an IoT Chipset
Meeting Industry Figure 1: IoT Device Operating in Smart Greenhouse
Some key high-tech monitoring applications in the agricultural sector are smart greenhouses, smart farming, precision farming and smart drones. Such technologies generate analytics that enable accurate decision making for optimum agricultural growth. The IoT system is often described as a network of physical and virtual devices that can communicate autonomously with each other using Internet Protocols (IP). IoT devices are embedded with sensors, software and connectivity capabilities. This enables them to collect and exchange data over the Internet across a variety of industries, not just agriculture.
The Persistent Threat to IoT Devices
According to National Geographic, there are about 100 lightning bolt strikes on the Earth’s surface every second. Each bolt can contain up to one billion volts of electricity. The National Severe Storms Laboratory (NSSL) estimates at least 30 million points on the ground are struck on average each year, just in the USA. Within residential or commercial building infrastructure, 80 percent of electrical transients that can impact IoT devices are generated by important equipment. These include pump motors, air conditioners, air compressors, blow motors, elevators, office copiers and more. Devices like these are where surges are generated on power
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Compliance Requirements There is an ever demanding need to ensure greater safety and reliability for IoT devices operating in the field. System designers are challenged with meeting industry compliance standards while also ensuring robustness of the system design for long life performance. Each new generation of IoT devices face growing transient threats from electrostatic discharges (ESD), electrical fast transients (EFT), surges, lightning, voltage spikes, or reverse polarity.
System design engineers must consider adequate overvoltage protection that does not degrade IoT transmission rates or create non- compliance with immunity standards. European Union regulations require end user modules such as IoT devices to meet CE compliance standards. They also require compliance with UL safety standards or compliance with EU low voltage directives.
Some of the standards that need adhering to include IEC 61850-3 for Industrial Communication Equipment, IEC 62052-11 for Metering Equipment, IEC 60601-1-2 for Medical Electrical Equipment, ISO 16750-2 12V & 24V for Road Vehicles, and ISO 21780 48V for Electric Vehicles. But there is more. Transmission protocol requirements such as IEEE Std 802.3 Ethernet Communication 10/100/1G/PoE/PoEP or USB 2.0- 3.2 Connector Specifications must also be considered. Each of the previously identified immunity standards will reference IEC 61000-4-2 Electrostatic Discharge (ESD), IEC 61000-4-4 Electrical Fast Transient (EFT), or IEC 61000-4-5 Surge requirements for the levels of transients applied to the AC/DC power supply or signal interfaces.
Figure 3: Graph of Applied IEC 61000-4-2 HBM ESD Pulse
The four levels of IEC 61000-4-2 are shown in
Table 1. They are up to plus or minus 8 kV contact / plus or minus 15 kV air discharges for ESD transients applied to systems. In some applications, a higher level is specified for enhanced contact and air discharge specifications. This is because human body models can reach plus or minus 25 kV in static-rich environments. To select appropriate ESD protection levels, designers must consider what external transients will be applied to equipment during installation or in operational mode in the field.
The IEC 61000-4-4 EFT Standard Electrical fast transients, also commonly referred to as fast transients or bursts, are a series of quick, high frequency pulses often caused by arcing. For example, power line transients occur when an AC/DC connection is made or broken, when equipment is powered down, or circuit breakers are switched. The pulse waveform for EFT is defined by a risetime of 5 ns, pulse width/duration of 50 ns, and burst duration of 300 ms.
The four levels of IEC 61000-4-4 are shown in
Table 2. They are up to plus or minus 4kV for EFT transients applied to systems using a 5/50ns pulse, as shown in Figure 4 using a repetition of pulses with a duration of 300ms.
ELECTRICAL ENGINEERING • NOVEMBER 2024 37
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