Adjustable Amplitude Ultrasonic Sensor for HVAC Noise Immunity
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Solution Overview
Problem
Ultrasonic occupancy sensors are prone to false triggering due to environmental noise such as forced air from HVAC systems, leading to unintended activation of electrical loads and energy wastage.
Innovation Solution
The implementation of an adjustable amplitude ultrasonic occupancy sensor system, which includes a microcontroller-controlled transmitter that adjusts output amplitude and a peak voltage detector circuit to analyze signals and adjust sensitivity levels, thereby reducing environmental noise-induced false triggering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ultrasonic transmitter outputs high amplitude signals to ensure detection range, then the sensor can detect occupancy over larger distances, but environmental noise such as HVAC airflow is more easily mistaken for occupancy signals causing false triggers
Solution Approach 1:
The patent implements dynamic adjustment of the ultrasonic transmitter's output amplitude based on detected environmental noise levels. The system continuously monitors the acoustic environment and automatically modifies transmission power to optimize the balance between detection range and noise immunity, preventing false triggers while maintaining occupancy detection accuracy.
Solution Approach 2:
The system changes the operating parameters of the ultrasonic transmitter by adjusting output amplitude dynamically. When environmental noise is detected, the system modifies transmission power levels to reduce the impact of noise on false triggering, while maintaining sufficient signal strength for valid occupancy detection.
2Measurement precision
If the ultrasonic receiver sensitivity is increased to detect weaker signals, then the sensor can detect occupancy in quieter environments, but the receiver becomes more prone to false triggering from environmental noise
Solution Approach 1:
The patent employs feedback mechanisms where the receiver monitors the acoustic environment and provides information back to the transmitter control system. This feedback loop enables the system to adjust transmission amplitude based on real-time noise conditions, creating a closed-loop control system that prevents false triggers while maintaining detection sensitivity.
Solution Approach 2:
The system dynamically adjusts receiver sensitivity settings based on environmental conditions. When high noise levels are detected, the system automatically modifies receiver thresholds to reduce false triggering, while maintaining the ability to detect valid occupancy signals through adaptive parameter adjustment.
3Power
If the ultrasonic transmitter operates at high power to ensure adequate signal strength, then the sensor maintains good detection performance, but the total internal system noise increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent applies partial action by transmitting ultrasonic signals at optimized power levels rather than maximum power continuously. The system adjusts transmission power to the minimum necessary level for adequate detection, reducing internal noise generation while maintaining sufficient signal strength for reliable occupancy detection.
Solution Approach 2:
The system dynamically changes transmitter power parameters based on detected occupancy conditions and environmental noise levels. When occupancy is detected or noise levels are high, the system reduces transmission power to minimize internal noise and improve signal-to-noise ratio, while maintaining adequate detection capability through adaptive adjustment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces false triggering by lowering the total ultrasonic energy and internal system noise, improving the signal-to-noise ratio and ensuring that only valid occupancy signals activate electrical loads.
Implementation Method 1
Active ultrasonic room occupancy sensors are equipped with an ultrasonic transmitter having an output with a generally fixed amplitude
Implementation Method 2
Ultrasonic occupancy sensors are sensitive to environmental noise such as forced air, e.g., from a HVAC vent, and other extraneous air pressure changes that may be interpreted by the ultrasonic receiver as a return ultrasonic signal
Data Source
AI summary
The adjustable voltage regulator under control of a microcontroller applies controlled amplitude voltage in the range of 5 to 9 VDC to the sensor transmitter to adjust the output amplitude of the transmitter. The adjustable amplitude transmitter allows an occupancy sensor to have its total output energy adjusted to reduce environmental noise-induced false triggering and to conform to the area to be covered. Lowering the total ultrasonic energy in the monitored space lowers the sensitivity of the receiver to inappropriate activations. Lowering the input power to the transmitter also lowers the total internal system noise and provides an improved signal to noise ratio in the receiver.