Determining power stealing capability of a climate control system controller
View Patent ↗Disclosed are exemplary embodiments of systems and methods for determining a power stealing capability of a climate control system controller. In an exemplary embodiment, a controller for use in a climate control system generally includes a capacitor chargeable by current flowing through an off-mode load of the climate control system. A voltage detect circuit detects a voltage across the capacitor. The controller includes a timer for determining a charge time of the capacitor from a first specific voltage to a second specific voltage based on input from the voltage detect circuit. The controller determines a resistance of the off-mode load based on the charge time and, based on the determined resistance, determines a level of current for power stealing through the off-mode load.
1. A controller for use in a climate control system, the controller comprising:
a capacitor chargeable by current flowing through an off-mode load of the climate control system;
a voltage detect circuit for detecting a voltage across the capacitor; and
a timer for determining a charge time of the capacitor from a first specific voltage to a second specific voltage based on input from the voltage detect circuit;
the controller being configured to determine a resistance of the off-mode load based on the charge time and based on the determined resistance, to determine a level of current for power stealing through the off-mode load; and
wherein the resistance of the off-mode load is determined in accordance with:
V t =V 0 +( V 1 −V 0 )×(1 −e −t/RC )
where V t represents a voltage across the capacitor at a time t, R represents a circuit resistance that includes the resistance of the off-mode load, C represents capacitance of the capacitor, and V 0 and V 1 represent the first and second specific voltages.
2. The controller of claim 1 , wherein the controller is further configured to control the life of a battery providing power to the controller, the controlling performed by adjusting a duty cycle of the controller based on the determined level of current for power stealing.
3. The controller of claim 1 , further comprising a power stealing circuit.
4. The controller of claim 1 , further comprising a current limiting circuit between the capacitor and the HVAC equipment.
5. The controller of claim 1 , wherein the controller is a thermostat.
6. The controller of claim 1 , wherein the controller uses the determined resistance and a lookup table to determine the level of current for power stealing.
7. A controller for use in a climate control system, the controller comprising:
a power stealing circuit for stealing power from an off-mode load of the climate control system;
a capacitor chargeable by current flowing through the off-mode load;
a voltage detect circuit for detecting voltages across the capacitor, including first and second specific voltages; and
a timer configured to determine a charge time of the capacitor from the first specific voltage to the second specific voltage as detected by the voltage detect circuit;
the controller being configured to:
determine a resistance of the off-mode load based on the charge time;
determine a power stealing capability of the power stealing circuit based on the determined resistance; and
adjust a duty cycle of the controller based on the determined power stealing capability; and
wherein the resistance of the off-mode load is determined in accordance with:
V t =V 0 +( V 1 −V 0 )×(1 −e −t/RC )
where V t represents a voltage across the capacitor at a time t, R represents a circuit resistance that includes the resistance of the off-mode load, C represents capacitance of the capacitor, and V 0 and V 1 represent the first and second specific voltages.
8. The controller of claim 7 , further comprising a current limiting circuit between the capacitor and the HVAC equipment.
9. The controller of claim 7 , wherein the controller is a thermostat.
10. The controller of claim 7 , wherein the controller uses the determined resistance and a lookup table to determine the level of current for power stealing.
11. A method of determining a power stealing capability of a controller of a climate control system, the method comprising:
determining a time duration for charging a capacitor of the controller from a first specific voltage to a second specific voltage, where the capacitor receives charge current through an off-mode load of the climate control system;
determining a resistance of the off-mode load based on the time duration; and
using the determined resistance to determine a level of current stealing by the controller through the off-mode load; and
wherein the resistance of the off-mode load is determined in accordance with:
V t =V 0 +( V 1 −V 0 )×(1 −e −t/RC )
where V t represents a voltage across the capacitor at a time t, R represents a circuit resistance that includes the resistance of the off-mode load, C represents capacitance of the capacitor, and V 0 and V 1 represent the first and second specific voltages.
12. The method of claim 11 , further comprising adjusting a duty cycle of the controller based on the determined current stealing level, the adjusting performed to control the life of a battery of the controller.
13. The method of claim 11 , wherein the controller is a thermostat.
14. The method of claim 11 , wherein the controller uses the determined resistance and a lookup table to determine the level of current for power stealing.