Feature: Hardware design


Figure 1: From brief to structure: (a) The original product brief; (b) The generated KiCad hierarchy separating the POWER, SENSOR and CONTROL_UI subsystems


Defining hardware requirements before


component selection


By Ruiwen Dong, Electronics Engineer, SpeedUp


also allow early part choices to define requirements that nobody has yet agreed. Consider a brief for a home temperature and humidity sensor that is battery powered, charges through USB-C and shows


A 16 October 2026 www.electronicsworld.co.uk


hardware project often appears to begin with component selection. Once the product brief arrives, it is tempting to choose the microcontroller, sensor, power supply and connectors, then draw the schematic around them. This creates visible progress, but it can


live readings on a small display. It identifies the product, but leaves most of the electrical design unspecified. It does not state measurement accuracy, update interval, battery life, charging temperature, display duty cycle, wake latency, environmental exposure or expected behaviour when the battery is flat. The purpose of hardware requirements is not to produce


paperwork before engineering begins. It is to convert product intent into measurable electrical constraints that guide architecture, component selection, schematic design and verification.


Turning product language into engineering limits A useful hardware requirement identifies the required behaviour, the condition under which it applies, a measurable limit and the intended verification method. “Long battery life” is not verifiable; however “the device shall operate for at least 12 months from a specified cell at 25°C whilst measuring once per minute and updating the display every minute” is. The distinction matters because each condition affects the


circuit. The measurement interval changes sensor and processor duty cycles. The OLED refresh interval changes the average display current. The lowest permitted battery voltage constrains the regulator and brownout threshold. The temperature range affects battery capacity, oscillator accuracy and component qualification. A real battery-powered temperature and humidity sensor


KiCad project illustrates the transition. Its original prompt specifies home use, battery power, USB-C charging, a small screen and real-time temperature and humidity. The resulting first-pass project divides the design into POWER, CONTROL_ UI and SENSOR sheets. It includes a BQ24074 charger, TPS63031 3.3V buck-boost regulator, ATTINY816 controller, CHT20MEMS sensor and OLED display, together with a BOM and editable KiCad source files; see Figure 1. Those parts make the architecture concrete, but they do


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