Capacitive Home Automation Transmitter with Battery Isolation
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Solution Overview
Problem
Existing capacitive detection transmitters for home automation face challenges in achieving compact dimensions while preventing untimely command transmissions during battery installation and pairing operations, due to the overlap of battery components with capacitive electrodes, leading to involuntary signals.
Innovation Solution
The transmitter design incorporates a cover with mechanical means to create a threshold greater than the capacitance variation caused by battery movement or contact, using a comparator to prevent command transmission until a finger's normal position is detected, and includes a time delay circuit to further prevent untimely emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a large diameter button battery is used to ensure several years of autonomy, then the battery can provide sufficient energy, but the battery covers the capacitive electrodes and causes involuntary command transmissions
Solution Approach 1:
A non-conductive spacer is introduced as an intermediary element between the battery and the capacitive electrodes. This spacer physically separates the battery from the electrodes, preventing the battery's presence from causing false capacitive signals while still allowing the battery to provide power. The spacer acts as a mediator that resolves the conflict between needing a large battery for autonomy and preventing the battery from interfering with electrode detection.
2Volume of moving object
If the transmitter is made compact to fit in decorative frames, then the thickness is reduced to about 10 mm, but the battery occupies the same space as the electrodes
Solution Approach 1:
The problem of spatial conflict between battery and electrodes in the thickness dimension is resolved by introducing a new dimensional layer - the non-conductive spacer. This spacer creates a dimensional separation that prevents the battery from directly contacting or interfering with the electrodes, effectively using an additional spatial dimension to resolve the overlap issue while maintaining the compact overall thickness.
3Measurement precision
If the threshold is set low to detect finger approach, then detection sensitivity is high, but battery movement causes false detections
Solution Approach 1:
The harmful capacitive effect of the battery is extracted or removed from the detection system by introducing the non-conductive spacer. This spacer effectively takes out the battery's interference from the capacitive detection circuit, allowing the threshold to be set low for high sensitivity without suffering from false detections caused by battery movement. The spacer isolates the battery's capacitive influence from the electrode measurements.
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 design ensures the transmitter remains compact, prevents untimely transmissions during pairing and battery installation, and maintains operational reliability by setting a detection threshold above the signal amplitude from battery movements or finger contact, ensuring accurate command issuance.
Implementation Method 1
capacitive sensing control points... make it possible to issue command activation commands when the user's finger approaches or lands on an external insulating plate, for example made of glass, masking a set of electrodes whose capacitance varies in the presence on point
Data Source
Figure 1~2
Figure 3~6
AI summary
Home automation transmitter (1) comprising: - an insulating outer plate (11) under which is arranged a front face (12a) of a printed circuit (12), the front face comprising at least one capacitive sensing electrode (4) providing a signal when there is a change in the capacitance of the sensing electrode, - a cover (7), - a compartment for a button cell battery (6), - a comparator comparing the signal to a threshold (5a) to cause the transmission of a control order by a control unit (2) of the transmitter, characterized in that the threshold is greater than the amplitude of the signal when there is a change in the capacitance of the sensing electrode due to a movement of the battery in its compartment and/or due to the contact of a finger on the battery through the opening.