How to avoid common electronics hardware engineering errors

There are many ways to arrive at a less-than-optimal electronics hardware solution. This article is an overview, not a comprehensive compilation of possible hardware engineering errors and how to avoid them.

Common errors include incorrect component selection, poor circuit design practices, such as grounding or signal integrity issues, improper power supply specifications, neglecting thermal management, and failing to adequately account for environmental factors like moisture or vibration.

Examples of errors related to both ac/dc and dc/dc power supply specification and integration include exceeding the maximum rating of key components, not considering the ability to support surge current demands from capacitive or inductive loads, and insufficient decoupling capacitors leading to voltage spikes on sensitive lines.

The power system must meet appropriate electromagnetic compatibility (EMC) requirements, including emissions and susceptibility to conducted and radiated electromagnetic interference (EMI). Additional considerations for AC/DC power supplies include sensitivity to surges and transients on the input line and a high power factor.

The location of power converters and specific types of loads like motors can result in hot spots that require extra attention during thermal design. Inadequate cooling due to insufficient heat sinking or inadequate airflow can lead to overheating, causing glitches and reducing operating lifetime.

Components must be compatible with the operating temperature range and anticipated humidity and have the needed power ratings. Circuit boards tie the system together, and layout errors can be serious. Improper trace routing can lead to crosstalk and signal integrity problems.

Trace width issues and incorrect trace spacings can reduce circuit integrity. Correct sizing and placement of ground planes is crucial, especially in high-performance systems.

Component placement requires careful consideration to avoid placing sensitive devices near high-power components where noise, EMI, and thermal factors can interfere with proper functioning. The integration of wireless connectivity brings unique PCB and system design challenges.

Modules can speed wireless circuit design

Designing the RF circuitry for wireless connectivity is complex and presents numerous challenges that can increase costs and delay time to market. Even if the circuit is correctly designed, the need for additional FCC certifications can be time-consuming and adds uncertainty.

Designing RF PCBs is different from designing circuits for sensors or digital logic. For example, maximum RF power transfer to the antenna is required, which requires matching the impedances of the transceiver circuit and the antenna.

That takes a properly designed RF transmission line on the PCB. Most designs need a 50-ohm transmission line to ensure maximum power transfer. The impedance is a complex transfer function that involves the transmission line and the adjacent ground planes, not simple resistance.

Designing the 50-ohm transmission line is complex, but it is not the only consideration. Most designs also need an LC matching circuit for fine-tuning to ensure maximum performance. Instead of dealing with the nuances of RF design, there are pre-certified RF modules for almost any protocol and frequency (Figure 1).

Figure 1. Wireless Bluetooth module ready for integration. (Image: Predictable Designs)

Hardware can cause software glitches

Once the design has been completed, a prototype built and testing has begun, glitches can appear. But the source may not be obvious. Hardware faults can cause software glitches.

Debugging systems with tightly coupled hardware and software is complex. Hardware faults can corrupt signal transmissions or variable values, leading to program execution errors. The results can look like software faults.

The potential sources are many and varied. Maybe there’s a bad solder joint in a hard-to-access location. Maybe critical component tolerances are adding up in a bad way. Maybe there are voltage margins to blame. Some fault sources can be easier to identify than others.

Faults like lower voltage margins can cause logic or communication link errors and be nondeterministic. That can make identifying the culprit difficult since their impact can be hard to distinguish from software errors like invalid memory access or exceptions in CPU operation. Data logging and careful monitoring of system operating conditions can help identify hardware errors masquerading as software or data anomalies (Figure 2).

Figure 2. Data logging and monitoring operating conditions can help identify hardware errors masked by software glitches. (Image: MDPI electronics)

Summary

Avoiding common electronics hardware engineering errors is all about the details: details related to power conversion and power distribution, details related to thermal management and environmental conditions, details related to component selection and placement, and details related to PCB layout. The use of pre-engineered modules can simplify and speed the integration of wireless connectivity. After the design is completed, hardware problems can be masked as software glitches.