Industrial power resistors play a key role in Industrial Internet of Things (IIoT) devices. We explore power resistor applications in IIoT and outline key considerations for selecting and implementing power resistors in these applications.
The Growth of IIoT
The term Internet of Things (IoT) was (allegedly) first used by Kevin Ashton in 1999. Rapid growth in RFID and M2M interfaces followed.
From 2010 onwards, interest in the Industrial Internet of Things (IIoT) grew rapidly. The phrase described the integration of machinery with networked sensors and software.
IIoT Power Management Challenges
IIoT systems rely on various devices. Sensors, actuators and gateways can all have distinct power needs. Power demands can shift based on operational states, like idle or active modes. As IIoT networks expand, it can become more difficult to maintain voltage across the network.
Power failures in critical IIoT systems can impact industrial operations. The challenge is to manage power distribution across numerous connected devices with varying power needs.
Industrial environments may have fluctuating power supplies due to heavy equipment usage. Power grid issues or integration with renewable energy sources can also have an impact. Heavy machinery operation may cause voltage dips or spikes. This can affect sensitive devices like sensors or computing units.
To prevent damage, IIoT systems must incorporate protection against overvoltage and undervoltage conditions. Noise on power lines can lead to transient voltage fluctuations, compromising device reliability if not properly regulated. Additionally, electromagnetic interference (EMI) from machinery and motors may degrade voltage regulation.
Battery-powered devices pose additional challenges, as battery discharge can cause voltage drops. Voltage regulators need to maintain consistent output, even as input voltage decreases. Ultra-low-power voltage regulators are critical for minimising energy consumption in battery-reliant IIoT devices.
Energy harvesting methods, such as solar or vibration-based systems, often generate insufficient energy. Environmental fluctuations, like light and motion, can impact energy harvesting efficiency.
Industrial Power Resistor Applications
Power resistors are found in a diverse range of IIoT devices including:
- Power management and voltage regulation circuits.
- Pulse protection circuits.
- Battery charging and protection circuits.
- Communication modules (e.g. RF circuits).
- Actuator control circuits.
- Energy harvesting circuits.
As the ability to sense and regulate current flow is critical for IIoT devices, current sense circuits are a common resistor application. To avoid signal interference, it is important to minimise parasitic inductance. This drives demand for surface-mountable devices.
Resistors are also common in voltage divider networks. Matching TCR and resistance values across resistors in the divider ensures consistent voltage output, which is crucial for stable power delivery.
Design Challenges in IIoT Power Resistors
When designing industrial power resistors for IIoT applications, the main design challenges include:
- Balancing power handling, thermal management and functionality
- Ensuring reliability in diverse environments
- Optimising for low power consumption
- Miniaturisation without compromising performance
Space constraints and high current flow in many IIoT applications often exclude wirewound and thin film resistors. The compact size and robust nature of thick film resistors, combined with their power handling capability, give them an advantage over other technologies in industrial power applications.
Resistors in IIoT applications must exhibit stability over extended operating periods. They must also be resistant to environmental factors such as moisture, chemicals and corrosion. Thick film resistors are the ideal choice for these demanding conditions.
When designing thick film resistors for IIoT applications, it is important to consider stability and long-term reliability.
Effective heat dissipation is crucial. Industrial power resistors in IIoT applications often experience prolonged exposure to high currents and thermal stress. While thick film resistors exhibit high power densities in a compact form factor, proper material selection, heat sinking and airflow design are essential.
In protection circuits, resistors are subjected to high-energy pulses or surges. Hence, designing for high pulse tolerance is critical to prevent damage. Additionally, industrial environments often have unstable or noisy power supplies. To mitigate these risks, power resistors must be designed with appropriate voltage ratings. Adequate spacing between terminals prevents dielectric breakdown or arcing.
Low voltage coefficient of resistance (VCR) resistors are preferred in IIoT applications to deliver reliable voltage regulation and maintain stability. A low Temperature Coefficient of Resistance (TCR) ensures that the resistor’s value remains stable across a wide temperature range.
The moderate VCR and TCR performance of thick film resistors is a reasonable compromise for many IIoT applications. Optimising the resistor design, material selection and production processes can improve these parameters.
When selecting industrial power resistors for IIoT applications, engineers must consider key parameters such as power handling, thermal management, pulse tolerance and environmental factors. There are trade-offs between size, performance, and cost.
Collaboration with specialist industrial power resistor manufacturers can yield solutions tailored to specific IIoT requirements. As IIoT continues to evolve, the role of power resistors remains critical in ensuring reliable, efficient and safe operation of industrial systems.