Wireless Thermostat Power Stealing for C-Wire-Free Connectivity
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Solution Overview
Problem
Current wireless-enabled thermostats require continuous power, which is not efficiently provided by existing power stealing methods, especially in systems without a C wire, leading to installation challenges and increased power consumption.
Innovation Solution
A power stealing circuit that intercepts power from the 'on-mode' load of a climate control system, such as a compressor or gas valve, to charge a capacitor, enabling intermittent wireless network connections and adjusting sleep times based on charging progress, thereby reducing power consumption and eliminating the need for a C wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power stealing is used to power the wireless network interface, then power consumption is reduced, but wireless connectivity becomes intermittent due to capacitor charging time
Solution Approach 1:
The wireless network interface operates in periodic cycles, alternating between active communication mode and sleep mode. The thermostat connects to the wireless network, performs data transmission, then enters sleep mode while the capacitor recharges through the power stealing circuit. This periodic operation allows the system to maintain wireless connectivity functionality while adapting to the intermittent power availability from power stealing.
Solution Approach 2:
The system dynamically adjusts its operation based on capacitor charge state. The control circuit monitors the capacitor voltage and dynamically switches between operational modes - when the capacitor is sufficiently charged, the wireless interface becomes active; when voltage drops below threshold, the system transitions to sleep mode to allow recharging. This dynamic adaptation resolves the contradiction between maintaining connectivity and managing limited power supply.
2Use of energy by moving object
If the thermostat connects intermittently to the wireless network, then power consumption is reduced, but data transmission efficiency decreases
Solution Approach 1:
The system maintains continuous useful action by ensuring that during each active window, critical data transmission tasks are completed efficiently. The capacitor is charged during sleep periods to ensure sufficient energy is available for uninterrupted data transmission during connect periods. This approach maintains productivity by ensuring that when the system is active, it can complete its communication tasks without interruption, while the intermittent nature of these active periods maintains low overall power consumption.
3Ease of manufacture
If power is stolen through the on-mode load, then installation without C wire is enabled, but power availability varies with load current
Solution Approach 1:
The power stealing circuit draws power from the existing on-mode load current without requiring additional wiring or a dedicated C wire. The circuit automatically captures and stores energy from the load current through the capacitor, making the system self-sufficient for powering the wireless interface. This self-service approach enables easy installation in existing systems while the capacitor-based energy storage ensures reliable operation despite variations in load current.
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
Enables continuous or nearly continuous wireless connectivity in climate control systems without a C wire, reducing power consumption and installation complexities by utilizing the 'on-mode' load for power sourcing, allowing for efficient and frequent network connections.
Implementation Method 1
A power stealing circuit of the thermostat is configured to steal power through an 'on-mode' load of the climate control system
Implementation Method 2
charge a capacitor or other energy storage device to provide the power for the wireless network interface
Data Source
AI summary
Disclosed are exemplary embodiments of apparatus, systems and methods for power stealing for a wireless-enabled thermostat. In an exemplary embodiment, a wireless-enabled thermostat generally includes a control having a wireless network interface that intermittently connects the thermostat in a wireless network in accordance with a duty cycle, the duty cycle having a connect time in which the thermostat is connected in the wireless network and a sleep time in which the thermostat is not connected in the wireless network. A power stealing circuit of the thermostat steals power through an “on-mode” load of a climate control system to charge a capacitor or other energy storage device to provide the power for the wireless network interface. The control adjusts at least the sleep time in accordance with a time for charging the capacitor or other energy storage device to a threshold voltage.