Temperature controller for low voltage thermoelectric cooling or warming boxes and method therefor

A control system for a thermoelectric device to maintain the temperature in a storage compartment at a set point, said control system comprising:

• a pair of input terminals for receiving a DC voltage thereacross;
• a pair of output terminals for connecting to the thermoelectric device;
• a first switch means operatively connected between one terminal of the pair of input terminals and one terminal of the pair of output terminals, said first switch means connecting said one terminal of the pair of input terminals to said one terminal of the pair of output terminals when enabled by the application of the DC voltage to said pair of input terminals with a predetermined polarity of the DC voltage being applied to said one terminal of the pair of input terminals;
• a second switch means operatively connected between the other terminal of the pair of input terminals and the other terminal of the pair of output terminals, said second switch means connecting said other terminal of the pair of input terminals to said other terminal of the pair of output terminals when said second switch means is enabled;
• a first diode network operatively connected between said first and second switch means for electrically connecting said first switch means and said second switch means and enabling said second switch means when said first diode network is enabled;
• coupling means operatively connected to said first diode network to enable said first diode network when said coupling means is enabled;
• sensor means providing an output indicative of the temperature in the storage compartment;
• programmable control means receiving the output from said sensor means and providing an output to said coupling means to enable said coupling means, said output from said programmable control means being determined by the amount of deviation of the sensed temperature in the storage compartment from the set point temperature;
• and
• a second diode network operatively connected between said pair of input terminals and said programmable control means to provide the correct polarity of the DC voltage to said programmable control means regardless of which input terminal of the pair of input terminals is provided the plus polarity of the DC voltage.