Building automation systems have a variety of functions to improve the comfort and safety of workers in industrial and commercial environments. Through innovative microcontroller (MCU) technology, these functions can become more intelligent and economical. In order to design better building automation solutions, appropriate components should be selected to realize the different functions of these applications. The use of special MCU can make the system detect, sense and control a variety of parameters in the working environment, so as to increase the flexibility of design.

Precise detection and sensing of motion: PIR solution

Passive infrared or pyroelectric infrared (PIR) sensors are commonly used in security systems and motion detection applications. You can choose a variety of different technologies to integrate the PIR solution into the motion detection system to detect whether there are “hot” objects or people passing in front of the sensor. PIR needs low power consumption, small components, low noise and high-precision sensing in any case, so as to accurately detect the infrared radiation of objects or people.

Motion sensors usually use analog band-pass filters, although the design of such filters is complex. The discrete simulation method is vulnerable to noise (through capacitors), which may produce low-frequency noise affecting motion detection. In contrast, the intelligent analog combination integrated in microcontrollers such as msp430fr2355 can provide the whole signal chain of PIR sensor, adjust the sensitivity and detection range through software configuration, provide digital feedback loop, and optimize the low-power performance of the sensor. PIR sensor based on MSP430 MCU has many advantages. See Figure 1 for details.

  

Figure 1: advantages of analog PIR & MSP430 signal conditioning technology

Neither digital analog nor digital PIR solutions can easily adapt to changing ranges, target speeds, ambient temperatures and lighting conditions. Ti’s test results show that the PIR motion sensor designed with MSP430 MCU can detect motion 36 feet (11 meters) away without analog and digital signal processing.

Digital PIR solutions with integrated signal chains are simple to design, but may be more expensive. MSP430 MCU integrates the signal chain into MCU, maximizes the battery life by using the low-power mode of MCU, realizes low noise, low power consumption (≅ 6ua) and high-performance signal chain, and applies it to motion detection. Compared with similar digital PIR solutions, using fewer components can make the printed circuit board smaller and the layout simpler, which can save up to 20% of the bill of materials cost.

Motor control: camera motor module

Automated security applications, including Internet protocols and video conferencing cameras, require automatic control of tilt, focus and aperture. These cameras pan, tilt and adjust the lens focus through electric or manual control modules. The motor module is powered by an external power supply unit, and the microcontroller in the unit must communicate with the motor driver to generate the control signal required for full operation.

The motor control design in Figure 2 uses a special msp430fr2155 MCU and two drv8428 stepper motor drivers. MSP430 MCU can control a variety of internal motor functions, including:

• motor speed

• direction of rotation

• voltage output of DC motor

• stepper motor position with universal asynchronous receiver / transmitter

• reduce power consumption when the system is not running

  

Figure 2: block diagram of motor module with MSP430 MCU and drv8428 motor driver

Two drv8428 stepper motor drivers realize focus and tilt control through precision subdivision driver (1 / 256 micro step) and current adjustable function, which is equivalent to DC motor. Another drv8837c brushless DC motor driver is used to control the aperture to protect the system from short circuit, undervoltage and temperature overheating. The solution can provide a variety of modes to achieve super smooth and stable motion curves.

epilogue

High precision detection, sensing and control through MSP430 MCU can optimize the performance of building automation and improve efficiency. You can read our application report in depth and then evaluate it using our launchpad development kit.

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