Smoke Sensor Circuit Feedback for Low-Power Pulsed Detection
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Solution Overview
Problem
Conventional smoke sensors require continuous monitoring of room air, which is energy-intensive and reduces battery life, necessitating a more efficient circuit arrangement for energy-saving and reliable smoke detection.
Innovation Solution
A circuit arrangement with a photodiode, input amplifier, and compensation current source, featuring a feedback network with switches and capacitors that quickly sets the operating point, reducing activation time and power consumption, and includes a self-test mode to compensate for noise and dark current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous monitoring of room air is implemented, then measurement precision is improved, but use of energy increases significantly
Solution Approach 1:
The patent implements periodic pulsed measurement instead of continuous monitoring. The transmitter emits light signals in periodic pulses, and the measuring unit performs measurements at discrete time intervals. This periodic action maintains measurement capability while significantly reducing energy consumption compared to continuous operation.
2Duration of action of moving object
If larger battery is used to provide more energy, then duration of action is extended, but device complexity and size increase
Solution Approach 1:
By switching from continuous to periodic pulsed operation, the energy consumption is dramatically reduced, allowing the same battery to provide much longer service life (potentially quadrupled as stated in the patent) without increasing battery size or device complexity.
Solution Approach 2:
The patent includes a test mode that can be activated before normal operation to characterize the input amplifier and compensate for noise influences. This preliminary characterization allows the system to operate more efficiently during normal measurement, extending battery life without requiring additional energy capacity.
3Productivity
If measurement time is reduced for faster response, then productivity is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent replaces traditional continuous analog measurement with pulsed optical measurement and digital signal processing. The photodiode detects light pulses, and the evaluating unit processes the digital signals to determine smoke presence. This substitution enables fast pulsed measurement while maintaining precision through digital evaluation and noise compensation techniques.
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 significantly reduces power consumption, extending battery life and enabling faster measurements, with the battery life of smoke sensors potentially quadrupled compared to conventional designs.
Implementation Method 1
The circuit arrangement has a photodiode for the optical measurement of particles in the measurement chamber. The photodiode detects the transmission signal that hits the diode after passing through the measuring chamber.
Implementation Method 2
The feedback includes a feedback network formed from at least one capacitance and at least one switch
Data Source
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AI summary
Smoke sensor (1) and circuit arrangement (10) for a smoke sensor (1) with a measuring chamber (2), wherein the circuit arrangement (10) comprises an optical transmitter (6) which emits a measurement signal into the measuring chamber (2), a photodiode (12) for optically measuring the measurement signal after it has passed through the measuring chamber, an input amplifier (28), and a compensation current source (22). The input amplifier (28) is supplied with an input current generated by the photodiode (12). It has feedback from an input amplifier output (36) to an input amplifier input (32). The feedback comprises a feedback network (38) formed from at least one capacitor (56) and at least one switch (58).