How to design a Car’s HVAC System?

hvac system

How to design an advanced auto HVAC system?

HVAC (heating, ventilation, and air conditioning) is the technology of indoor and automotive environmental comfort. These days HVAC systems are available in most of the mid and high end automotive. Traditional HVAC systems were mostly electromechanical with mechanical knobs to adjust air flow vents, cooling control, blower speed etc.

NXP offers the MPC560xS/MPC5645S microcontroller based HVAC system that is designed to replace existing mechanical switches based system with TFT LCD and resistive touch-based interactive system.

MPC5606S/MPC5645S based HVAC System Design


The HVAC design comprises all the basic features of HVAC system and adds some user-friendly advanced features for better controllability.

Basic features

Basic features include Airflow Vent Control, Blower Speed Control (5 Level), Cool/Warm Control, Defogger On/Off,  Recirculation On/Off and Air Conditioning On/Off.

Airflow Vent Control

The design consists of the five basic air flow vent control icons on the TFT LCD screen instead of mechanical rotator switch. The placement of icons gives the comfort of choosing any particular vent position in a single tap/ key press.

Blower Speed Control (5 Level)

A five-stage blower speed selection is provided on the screen. On tapping/key press an enlarged screen pops up to ease the selection even from rear-seat. The speed control could be implemented as analog control with very fine step size but is currently limited to five steps for comfort of user in switching from mechanical systems to advanced TFT LCD based systems.

Cool/Warm Control

An analog slider is implemented for the cooling control. On tapping/button press, similar to speed control, cooling control slider also enlarges and eases the selection. The analog slider is kept analogues to slider control in traditional mechanical systems but step size can be reduced to a much larger extent in advanced system.

  • Defogger On/Off
  • Recirculation On/Off
  • Air Conditioning On/Off
Indoor Reference Design for Smart Buildings and Homes

Advanced features

In order to take the HVAC technology further closer to comfort and luxury various advanced features are implemented in the design. Some of them include Cabin temperature display, Date display, Time display, LIN and CAN for communication, actuator motor stall detection, Blower motor stall detection, System control interfaces (IR remote control, Resistive touch control, RF remote control), Audio warnings for hazard reporting, and QSPI memory for high end graphics.

The following items will be supplied to the user for developing the HVAC system using the Freescale MPC560xS/MPC5645S controller:

  • Reference HVAC system.
  • Software – Source code
  • Documentation – DRM, BOM, Schematics.

For further details, click here.




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