In any vehicle, the instrument cluster forms a critical part as it is the face of the vehicle that reflects the current state. Apart from providing basic vehicle information, it can also provide crucial indications of electrical component malfunctions (EFI/ISG related). Clusters can acquire vehicle data over simple mechanisms such as encoders as well as through complex interfaces such as CAN and SAEJ1850.
Instrument cluster design for electric vehicles presents a unique challenge: the system may carry less mechanical complexity compared to combustion counterparts, yet the electric vehicle instrument cluster must be more user-friendly, less power-hungry, and delivered as a cost-effective solution. Careful design and component selection are necessary to meet stringent compliance requirements. Among all constituent components, the MCU carries the most weight — and only a few vendors support automotive-grade MCUs with the required feature sets for a robust electric vehicle instrument cluster.
Embien'automotive engineering team has delivered multiple Instrument Cluster Design projects across OEM, Tier 1, and Tier 2 supply chains, spanning heavy-duty trucks to lightweight electric scooters. Visit our industries page to see the full range of domains we serve.
Instrument Cluster Design: Subsystem Overview
A complete Instrument Cluster Design integrates several subsystems that together present the driver with real-time vehicle status. Understanding each subsystem is key to building an effective electric vehicle instrument cluster. The major components and their functionalities are as follows:
- Gauges: Generally, three gauges — RPM, Temperature, and Fuel/Battery Level — are indicated by the cluster.
- Fuel/Battery Gauge: The gauge ranges from Empty (E) to Full (F). In electric vehicles, this gauge tracks state-of-charge rather than fluid level. The signal received from the sensor is analog; pointer position depends on the incoming resistance or voltage value.
- RPM Gauge: The signal received from the RPM sensor (encoder with tach terminal, signal and ground wire) is treated as a frequency input. Based on the vehicle type and top speed, the input range varies.
- Temperature Gauge: The signal from the temperature sensor is analog, realized with a thermistor and two-wire connection. A front-end circuit converts input resistance to a corresponding voltage, which the microcontroller reads as the current temperature.
- Seven-Segment Displays: Clusters may use segmented displays in various resolutions (27×4, 39×4, 48×4, 53×4, or 54×4) to show odometer readings, trip distance, hour meter data, and similar information.
- Telltales: Telltales are regulatory indicators typically realized with LEDs that show the state of key components — low battery, engine faults, high beam, and more. They are usually implemented with onboard LEDs and mechanical light guides, with graphical overlays carrying standard tell-tale symbols.
- Switches: A single push switch or rotatable push-type switch allows the driver to toggle information shown on the display, such as trip distance or time.
Feature set and component selection will vary by vehicle manufacturer, but the overall Instrument Cluster Design architecture remains consistent across platforms.
Renesas RL78 IoT Solutions for Electric Vehicle Instrument Clusters
Renesas is a leading semiconductor company in the automotive space, offering cluster MCUs for many decades. The Renesas RL78 IoT solutions portfolio provides ultra-low-power microcontrollers that are automotive-grade and well-suited for realizing a complete electric vehicle instrument cluster. While there are architectural differences across the RL78 family, the core subsystem for cluster applications remains consistent.
The high-level block diagram of the RL78 MCU-based electric vehicle instrument cluster is shown below:
The Renesas RL78 IoT solutions make it straightforward to realize vehicle clusters effectively with a feature-rich peripheral set:
Microcontroller: The RL78 MCU delivers high performance within the low-end MCU space. It offers improved efficiency, extensive scalability, and reliable safety functions that aid in developing energy-efficient electric vehicle instrument clusters. Operating voltage ranges from 2.7V to 5.5V, with an 80-pin package suitable for compact cluster PCBs.
Stepper Motor Drivers: Up to three channels of stepper motor controllers with zero-point detection are configurable via PORT pins (Sin+, Sin−, Cos+, Cos−). Each channel controls a dedicated gauge needle, commanding the motor to move and hold at an angle without a position sensor. Software-based PID control ensures precise needle movement.
Segment LCD Controller: The built-in LCD controller can drive 200+ segments, supporting display resolutions of 27×4, 39×4, 48×4, 53×4, and 54×4 — all directly driven from the RL78 microcontroller. The LCD screen is software-controlled to display dynamic data such as trip information and hour meter readings.
Multiple IOs: Multiple analog and digital IOs are available for interfacing sensors and tell-tale LEDs. RPM, temperature, and fuel/battery sensors connect via suitable front-end circuits. Digital outputs drive tell-tale LEDs for indicators such as turn signals, service alerts, and brake warnings.
- Analog Input Gauges: The RL78 series includes a rich ADC input set that converts resistance/voltage-based sensor inputs to digital values. Software processing increases measurement accuracy.
- Encoder Inputs: With up to 24 timers, the RL78 measures encoder inputs such as RPM, applies custom processing, and yields accurate digital values.
- External Connectivity: I2C/SPI interfaces connect to peripherals such as EEPROM (for storing odometer and trip data) and RTC modules for real-time tracking.
Variants within the Renesas RL78 IoT solutions family also include a sound generator (configurable volume and tone frequency), two CAN channels for vehicle network integration, and expanded flash/RAM up to 512 KB/24 KB — making them well-suited for low-end to mid-range electric vehicle instrument cluster designs.
Graphical Instrument Clusters with RL78
Modern electric vehicle platforms increasingly demand graphical instrument clusters that go beyond simple needle gauges and seven-segment displays. Graphical instrument clusters combine LCD panels, animated icons, and theme-based rendering to present speed, battery state, navigation hints, and ADAS alerts in a visually rich format. The RL78 series, when paired with an external graphics controller or a higher-end variant supporting parallel display interfaces, can serve as the host MCU for graphical instrument clusters in cost-sensitive vehicle lines.
Digital Instrument Cluster for Two-Wheelers
The Renesas RL78 family has proven especially popular in the two-wheeler segment. A digital instrument cluster for two-wheelers must operate within tight power budgets, survive vibration and temperature extremes, and present battery charge level, speed, and telltale status at a glance. The RL78's ultra-low standby current, integrated LCD controller, and three-channel stepper motor drive make it an ideal choice for a digital instrument cluster for two-wheelers — from entry-level electric scooters to premium electric motorcycles.
Embien's Expertise in Automotive Instrument Cluster Design
Embien Technologies is a leading embedded systems development company specializing in high-tech product engineering. With a unique mix of innovation, technology, and quality, our automotive engineering practice delivers cutting-edge electric vehicle instrument cluster solutions by leveraging the latest technologies in clusters, diagnostics, infotainment, and connectivity.
We have assisted several OEMs, Tier 1, and Tier 2 vendors in advancing their Instrument Cluster Design efforts — covering heavy and light-duty vehicles, digital cockpits, and electric powertrains. Our work spans integration of sensors and radars, CAN network connectivity, and path planning and mapping technologies. Explore the full scope of our work across the industries we serve.
Do you have an electric vehicle instrument cluster design challenge? Get in touch with our team today.