Thermal photocontrol switch circuit

A circuit having an input and an output and configurable for power sources of more than one voltage, comprising:

• an input for connection to a source;
• an output for connection to a load;
• a heating element that dissipates heat responsive to a current flow through the circuit;
• a series resistor connected to said heating element;
• and
• a bypass shunt connected in parallel with said series resistor, said bypass shunt having at least one connection formed of a meltable material, said one connection located in proximity to said heating element so that dissipation of heat by said heating element above a predetermined level sufficient to melt said connection opens said bypass shunt to configure said circuit for another voltage.

A method of self-configuring a photocontrol circuit for use with power sources of more than one voltage, comprising the steps of:

• connecting an input to a power source;
• connecting an output to a load;
• providing a heating element in a conductive path between the input and a neutral terminal;
• operating a switch in a conductive path between said input and said output in response to heat dissipated by said heating element;
• bypassing a series resistor with a tensioned shunt located in the conductive path between said input and said neutral terminal;
• melting a connection at an end of said shunt to allow said tensioned shunt to relax thereby preventing the bypassing of said series resistor when said input is connected to a power source of a higher voltage.

A method of manufacturing a dual-range self-configuring photo control circuit that has an input for connection to a power source and an output for connection to a load, a photocell responsive to ambient light, a heating resistor connected to said photocell, a bimetallic element in proximity to said heating resistor and movable in response to generation of heat from said heating resistor from a first position to a second position, a switch connecting between said input and said output, said switch operated by said bimetallic element, and a series resistor connected to said heating resistor, the method comprising the steps of:

• connecting one end of a shunt to a location at one end of the series resistor such that the other end of said shunt is a distance away from the other end of said series resistor;
• bending said shunt so that said other end is in electrical contact with the other end of series resistor and in proximity to the heating resistor;
• and
• making a stable connection between the other end of shunt and the other end of the series resistor by means of a meltable solder so that the shunt forms a bypass across said series resistor so long as the solder does not melt.