Protective circuit for an apparatus

Abstract

The invention is directed towards a protective circuit for an apparatus including an accelerometer having an output and a microcontroller coupled to the output of the accelerometer. The protective circuit also includes a switch for controlling the apparatus coupled to an output of the microcontroller and a load coupled to the switch. A power source is coupled to the load and the switch. In operation the microcontroller is cable of sending a signal to the switch to turn of power to the load when a dangerous condition has occurred. Also, the invention is directed toward a method of controller an apparatus with the protective circuit.

1 . A protective circuit for an apparatus, comprising:
 an accelerometer having an output;   a microcontroller coupled to the output of the accelerometer;   a switch for controlling the apparatus coupled to an output of the microcontroller;   a load coupled to the switch; and   a power source coupled to the load and the switch.   
     
     
         2 . The circuit of  claim 1 , wherein the accelerometer is a two-axis MEMS accelerometer. 
     
     
         3 . The circuit of  claim 2 , wherein the two-axis accelerometer includes a first axis in a y-direction and a second axis in an x-direction. 
     
     
         4 . The circuit of  claim 1 , wherein the accelerometer is a three-axis MEMS accelerometer. 
     
     
         5 . The circuit of  claim 1 , wherein the apparatus is selected from the group consisting of an electric iron, an electric soldering iron, and an electric heater. 
     
     
         6 . The circuit of  claim 1 , wherein the microcontroller outputs a control signal to turn off the switch when it receives output values of the accelerometer that are substantially equal to predetermined values. 
     
     
         7 . The circuit of  claim 2 , wherein the microcontroller outputs a control signal to turn off the switch when it receives a first output value of the two-axis accelerometer in an x-direction at about 1 G and a second output value of the two-axis accelerometer in a y-direction at about 0 G. 
     
     
         8 . The circuit of  claim 1 , wherein the power source is a DC power source. 
     
     
         9 . A protective circuit for an appliance, comprising:
 a two-axis MEMS accelerometer having a first axis in a y-direction and a second axis in an x-direction;   a microcontroller coupled to an output of the two-axis MEMS accelerometer;   a switch to turn on or off the small appliance coupled to an output of the microcontroller, wherein the microcontroller is configured to turn off the switch when the appliance is in a predetermined orientation for a predetermined period of time;   a load coupled to the switch; and   a power source coupled to the load and the switch.   
     
     
         10 . The circuit of  claim 9 , wherein the appliance is selected from the group consisting of an electric iron, an electric soldering iron, and an electric heater. 
     
     
         11 . The circuit of  claim 9 , wherein the appliance is an electric iron and the predetermined orientation includes at least the iron arranged on a heating surface. 
     
     
         12 . The circuit of  claim 9 , wherein the appliance is an electric iron and the predetermined orientation includes at least the iron arranged on a side surface. 
     
     
         13 . The circuit of  claim 9 , wherein the predetermined period is greater than about 5 minutes. 
     
     
         14 . A method of controlling an apparatus, comprising the steps of:
 periodically reading values from a MEMS accelerometer, wherein the values include a first gravitational measurement in a first direction and a second gravitational measurement in a second direction being substantially perpendicular to the first direction;   comparing the first and second gravitational values with a previous first and second gravitational value;   incrementing a no motion counter when the first and second gravitational values are within a first predetermined range of a previous first and second gravitational values;   resetting the no motion counter to zero when the first and second gravitational values are within a second predetermined range of the previous first and second gravitational values;   comparing the no motion counter to a predetermined first maximum no motion counter;   comparing the first and second gravitational values with a predetermined first and second gravitational values when the no motion counter is greater than the maximum no motion counter; and   sending a signal to turn off load to an apparatus when the first and second gravitational values are within a predetermined tolerance of the predetermined first and second gravitational values.   
     
     
         15 . The method of  claim 14 , wherein the predetermined tolerance is less than 10 percent. 
     
     
         16 . The method of  claim 14 , wherein the apparatus is selected from the group consisting of an electric iron, an electric soldering iron, and an electric heater. 
     
     
         17 . The method of  claim 14 , wherein the periodic interrupt is performed in range of about 1 ms to about 1000 ms. 
     
     
         18 . The method of  claim 14 , wherein the predetermined first and second gravitational values comprise about 1 G for the first gravitational value and about 0 G for the second gravitational value. 
     
     
         19 . The method of  claim 14 , wherein the apparatus is an electric iron having a toe, a heel, a first side and a second side, and a heating surface and the predetermined gravitational values are selected to correspond to a condition representing at least one of the following orientations of the apparatus the electric iron being positioned on the heel, the electric iron being positioned on the heating surface, and the electric iron being positioned on either the first side or the second side. 
     
     
         20 . The method of  claim 14 , wherein the MEMS accelerometer is a three-axis accelerometer.