DC thermostat with latching relay repulsing
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Solution Overview
Problem
Battery-powered thermostats with latching relays are prone to mechanical shocks and voltage fluctuations, leading to improper latching states, which can result in incorrect operation of heating and cooling systems, potentially causing comfort space temperature instability and damage due to failed furnace or air conditioning cycles.
Innovation Solution
A microprocessor-controlled thermostat that monitors battery voltage and temperature, incorporates re-pulsing functionality to ensure proper latching of relays, adjusts temperature setpoints and pulse widths to compensate for mechanical interference and battery degradation, and provides alerts for low battery conditions to prolong battery life and maintain system reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a latching relay is used to maintain relay state without continuous power, then battery life is extended, but the relay contact becomes vulnerable to mechanical shock and voltage fluctuations causing improper latching
Solution Approach 1:
The patent implements periodic repulsing of the latching relay contact at predetermined intervals (e.g., every 4 hours) to reset and verify the latching state. This periodic action prevents the relay from drifting into incorrect states due to mechanical shock or voltage fluctuations while maintaining the battery-powered operation that extends battery life.
Solution Approach 2:
The microprocessor monitors the relay latching state and implements feedback control by detecting improper latching conditions (such as when the relay state does not match the expected heating/cooling demand) and automatically triggering repulsing actions to correct the state, thereby maintaining reliability without continuous power consumption.
2Reliability
If the thermostat continuously monitors and corrects relay latching state, then operational reliability is improved, but battery power consumption increases
Solution Approach 1:
Instead of continuous monitoring, the system performs relay repulsing at predetermined periodic intervals (e.g., every 4 hours) only when heating or cooling is demanded. This reduces battery power consumption compared to continuous monitoring while still maintaining operational reliability through periodic verification and correction of latching states.
Solution Approach 2:
The system performs repulsing actions in advance at predetermined intervals before improper latching can cause operational errors. By proactively resetting the relay state periodically, the system prevents potential failures rather than continuously detecting and correcting them, thereby reducing power consumption while maintaining reliability.
3Measurement precision
If repulsing is performed at frequent intervals to ensure proper latching, then relay state accuracy is improved, but battery life is reduced
Solution Approach 1:
The system strikes a balance by implementing repulsing at predetermined moderate intervals (e.g., every 4 hours) rather than frequently or continuously. This periodic approach maintains sufficient relay state accuracy for reliable operation while avoiding excessive battery power consumption that would result from more frequent repulsing actions.
Solution Approach 2:
The system performs repulsing only when heating or cooling is demanded, rather than at all times. This partial action approach provides sufficient latching state accuracy during active HVAC operation while conserving battery life during periods when the HVAC system is not running, optimizing the trade-off between reliability and power consumption.
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 solution ensures reliable operation of heating and cooling systems by maintaining proper latching states and reducing battery energy consumption, thereby preventing temperature instability and potential damages such as frozen pipes or stress to indoor plants and pets.
Implementation Method 1
The latch mechanism in most latching relays relies on the magnetic force of the contact to keep the contact latched ON or latched OFF.
Implementation Method 2
A voltage applied across a relay coil generates a magnetic field that acts on a latching relay contact
Data Source
AI summary
A thermostat, of the type that employs latching relays to connect thermostat power to the various wires of the thermostat run, has a re-pulse feature that supplies latching pulses at a given interval, e.g., three hours, to ensure that the relays are in their proper state agreeing with the thermostat mode and the room temperature relative to the setpoint(s). In the case that the room air temperature is changing in a manner contrary to the current heating or cooling mode, which may indicate the latching relay has been knocked or bumped and needs to have its proper state re-established, the thermostat microprocessor issues pulses to the latching relay(s) more frequently, e.g., each 30 minutes, and the re-pulses may have a longer pulse width, e.g., increased from 20 ms to 25 ms.