A temperature control device comprises: an operation amount upper limit setting part that sets an upper limit of an operation amount of a heater; and a temperature change rate comparing part that determines, in every prescribed time period, whether an actual measured change rate of the temperature of a body-to-be-heated with respect to time is outside a prescribed range that includes a target rate of change. The operation amount upper limit setting part sets the upper limit to a preset initial value when operation of the heater is started toward the target temperature, and updates the upper limit, in a period until the temperature of the body-to-be-heated reaches the target temperature, such that the difference between an actual measured temperature and a temperature locus that is represented using the target rate of change becomes smaller when it is determined that the actual measured change rate is outside the prescribed range.

The present disclosure is directed to an optical device including at least one temperature-dependent tunable element for controlling a wavelength of an optical signal, a first sensor configured to indirectly monitor the optical signal, a second sensor configured to directly monitor the optical signal, and a control circuit. The tunable element may be one of (i) a laser for transmitting an outgoing optical signal and (ii) an optical filter coupled to a photodetector for receiving an incoming optical signal. The control circuit may be configured to receive first and second inputs from the first and second sensors, respectively, adjust the tuned wavelength of the tunable element from a first preselected wavelength to a second preselected wavelength based on the first input received from the first sensor, and maintain the tunable element at the second preselected frequency based on the second input received from the second sensor.

A power harvesting system employs a saturable core transformer having first and second primary windings and a secondary winding. The first primary winding is a high impedance winding with a large number of turns and the second primary winding is a low impedance winding with a small number of turns. The first and second primary windings are connected to a load. A relay is operable in a first state to connect A/C power to the first primary winding and in a second state to connect A/C power to the second primary winding. When A/C power is connected to the first primary winding, a small current flows in the first primary winding which is insufficient to activate the load but sufficient to transfer power to the secondary winding. When A/C power is connected to the second primary winding, a larger current flows in the second primary winding sufficient to activate the load and to transfer power to the secondary winding.

A fluid heater includes a heating circuit, a temperature monitoring circuit, a controller, and an overheat sensing element. The controller is disposed in a control unit and is in circuit communication with a temperature gauge and a power supply switch, the controller being configured to operate the power supply switch in response to feedback from the temperature gauge to maintain the heater at a setpoint temperature. The overheat sensing element is disposed in a heater housing proximate to a thermal fuse and is in circuit communication with the controller to provide an indication to the controller when the overheat sensing element reaches an overheat temperature lower than the critical temperature. The controller is configured to operate the power supply switch to reduce or shut off power to the heating element in response to receiving the indication that the overheat sensing element has reached the overheat temperature.

A temperature limiting device for a thermal system includes a modular unit that is configured to connect to a two-wire heater of the thermal system. More particularly, the modular unit includes a heater interface configured to connect to a two-wire heater of the thermal system, a power interface configured to connect to a power source to receive power; and a controller including a sensor circuit. The sensor circuit is configured to measure an electrical characteristic of the two-wire heater, which includes voltage, current, or a combination thereof. The controller is configured to calculate a temperature of the thermal system based on the measured electrical characteristic and determine whether the temperature is greater than a temperature setpoint.

A power harvesting system employs a saturable core transformer having two primary windings and at least one secondary winding. One of the primary windings is a high impedance winding, and the other primary winding is a low impedance winding. The two primary windings are connected with the load (motor). The secondary winding provides power to the circuit components of a replacement electronic thermostat. Relay contacts connects A/C power to either the high impedance primary winding or to the low impedance primary winding. When the relay is de-energized, A/C power is applied to the high impedance winding so that a relatively small amount of current flows through both the high impedance winding and the load. This current is low enough that it does not energize the load but is sufficient to generate the required voltage to transfer power to the secondary winding. This power can be used to power an electronic thermostat. When the relay is energized, A/C power is applied directly to the low impedance primary winding, energizing the load. At the beginning of each A/C cycle, the current through the low impedance winding builds up rapidly until the core saturates. The result is that a short pulse is generated in the secondary on both the positive and negative A/C cycle. This pulse has an amplitude determined by the turns ratio of the low impedance winding to the secondary winding and is used to power the electronic thermostat. After the core saturates, the impedance of the low impedance winding is only the resistance of the wire of the winding which is relatively small and results in negligible impact on the load.

The present disclosure is directed to an optical device including at least one temperature-dependent tunable element for controlling a wavelength of an optical signal, a first sensor configured to indirectly monitor the optical signal, a second sensor configured to directly monitor the optical signal, and a control circuit. The tunable element may be one of (i) a laser for transmitting an outgoing optical signal and (ii) an optical filter coupled to a photodetector for receiving an incoming optical signal. The control circuit may be configured to receive first and second inputs from the first and second sensors, respectively, adjust the tuned wavelength of the tunable element from a first preselected wavelength to a second preselected wavelength based on the first input received from the first sensor, and maintain the tunable element at the second preselected frequency based on the second input received from the second sensor.

The present disclosure is directed to an optical device including at least one temperature-dependent tunable element for controlling a wavelength of an optical signal, a first temperature control circuit for controlling a temperature of a first region of the optical device; and a second temperature control circuit for controlling a temperature of a second region of the optical device. The second region may include a portion of the first region. The second region may be smaller than the first region. The tunable element may be positioned in the second region such that a temperature of the tunable element is controlled based on the second temperature control circuit controlling the temperature of the second region. The tunable element may be one of (i) a laser for transmitting an outgoing optical signal and (ii) an optical filter coupled to a photodetector for receiving an incoming optical signal.

A method for controlling an electric fan including an electric motor and electronics for controlling the electric motor, including a step for controlling the speed of the motor, a step for controlling the power of the motor as an alternative to the step for controlling the speed; the step for controlling the power including a step for monitoring the electrical power P.sub.IN;FEEDBACK absorbed by the motor and a step for regulating the electrical power P.sub.IN;FEEDBACK absorbed by the motor including a step of applying a variation freq to the electricity supply frequency of the motor as a function of a difference between a power set-point PI.sub.IN, REF and the power absorbed by the motor PI.sub.IN,FEEDBACK.

A power harvesting system employs a saturable core transformer having first and second primary windings and a secondary winding. The first primary winding is a high impedance winding with a large number of turns and the second primary winding is a low impedance winding with a small number of turns. The first and second primary windings are connected to a load. A relay is operable in a first state to connect A/C power to the first primary winding and in a second state to connect A/C power to the second primary winding. When A/C power is connected to the first primary winding, a small current flows in the first primary winding which is insufficient to activate the load but sufficient to transfer power to the secondary winding. When A/C power is connected to the second primary winding, a larger current flows in the second primary winding sufficient to activate the load and to transfer power to the secondary winding.