Power-Strobed Piezoresistive Pressure Sensing for Low-Current Pushbuttons

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing pedestrian pushbutton sensors face challenges with high power consumption and vulnerability to vandalism and environmental damage, particularly in high-traffic areas with harsh climates, where piezoresistive sensors are not suitable due to their power requirements and susceptibility to damage.

Innovation Solution

A low-power sensor system utilizing a piezoresistive sensor with a strobing power supply that intermittently activates the sensor, reducing average current consumption to less than 500 microamps, and an adjustable construction to accommodate varying pressures, including a housing design with environmental seals to protect against weather and vandalism.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If piezoresistive sensors are used for pressure sensing, then sensing capability is improved, but power consumption increases to several milliamperes which exceeds the maximum allowable quiescent current

Engineering Contradiction:

Improvepressure sensing capabilityVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent applies periodic action by strobing power to the piezoresistive sensor in brief intermittent pulses rather than continuous power supply. The sensor is activated only during brief measurement windows, allowing it to maintain full sensing capability when needed while dramatically reducing average power consumption to below the 500 microamp threshold for pedestrian pushbutton applications.

Inventive Principle:

Principle #19Periodic action

2Measurement precision

If piezoresistive sensors are used in pedestrian pushbuttons, then pressure sensitivity is improved, but vulnerability to vandalism and environmental damage increases

Engineering Contradiction:

Improvepressure sensitivityVSAvoidvulnerability to vandalism and environmental damage

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent employs a disposable seal component that can be easily replaced. The seal is designed as a simple, inexpensive element that protects the sensitive piezoresistive sensor from environmental damage and vandalism. When the seal becomes compromised, it can be quickly replaced without replacing the entire sensor assembly, maintaining pressure sensitivity while providing robust environmental protection.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If continuous power is supplied to the sensor, then measurement accuracy is maintained, but average current consumption exceeds the rigid limit of a few hundred microamps

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidaverage current consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The system uses periodic strobing of power to the sensor, activating it only during brief measurement intervals. This allows the sensor to achieve full measurement accuracy when powered, while the average current consumption remains below the 500 microamp limit because power is supplied only during short measurement windows rather than continuously.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system performs preliminary actions by pre-planning measurement windows and strobing power in advance of actual measurements. The microprocessor controls power delivery to activate the sensor only when measurements are needed, ensuring measurement accuracy is maintained when required while minimizing overall power consumption through advance planning of power delivery timing.

Inventive Principle:

Principle #10Preliminary action

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

The system effectively reduces power consumption and enhances durability, ensuring reliable operation with minimal quiescent current while maintaining sensitivity to pressure changes, thus addressing the limitations of traditional sensors in harsh environments.

Implementation Method 1

The piezoresistive effect describes the change in electrical resistance (in the case of mechanical devices) or resistivity (in the case of semiconductor devices) when a mechanical stress is applied.

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Implementation Method 2

The piezoresistive effect describes the change in electrical resistance (in the case of mechanical devices) or resistivity (in the case of semiconductor devices) when a mechanical stress is applied.

Methodology Applied

Scientific EffectElectrical resistance change under stress: Piezoresistive Effect

Data Source

PatentUS8746086B1Extremely low power pressure sensing system using power strobed sensor

Publication Date: 2014.06.10 NIEMEYER THADDEUS J

AI summary

A sensing system has a sensor suitable for producing a signal relative to the sensing of a physical parameter, a power supply connected to the sensor, and a strobe interconnected to the sensor or to the power supply so as to pass power to the sensor so as to activate the sensor so as to cause the sensor to sense the physical parameter. The strobe intermitantly passes power at rapid rate to the sensor. A human interface device is cooperative with the sensor such that the sensor senses an operation of the human interface device. The sensor is a piezoresistive sensor. A processor is connected to the sensor so as to receive a signal from the sensor corresponding to the activation of the sensor by the strobe.