Control circuitry for thermoelectric environmental chamber

Circuitry for controlling a solid state thermoelectric device in a thermoelectric environmental chamber, said solid state thermoelectric device being in thermal communication with an internal heat exchanger disposed inside a thermal compartment of said thermoelectric environmental chamber and an external heat exchanger disposed outside of said thermal compartment, said circuitry comprising in combination:

• a. temperature selecting means for digital selecting of a temperature that is desired to be maintained in said thermal compartment;
• b. first means responsive to said temperature selecting means for producing a first current representative of said selected temperature;
• c. second means responsive to said first current for producing a first voltage representative of a first upper range limit of said selected temperature;
• d. third means responsive to said first current for producing a second voltage representative of a first lower range limit for said selected temperature;
• e. first temperature sensing means disposed in said compartment for sensing an actual temperature in said thermal compartment and producing a third voltage representative of said actual temperature;
• f. comparison means for comparing said third voltage to said first and second voltages to produce first information indicating whether said actual temperature is above said first upper range limit or below said first lower range limit;
• g. fourth means responsive to said first information for producing a first control signal;
• h. first switching means responsive to said first control signal for
• i. coupling a first terminal of said solid state thermoelectric device to a first supply voltage conductor and,
• ii. coupling a second terminal of said solid state thermoelectric device to a second supply voltage conductor,
• if said third voltage is greater than said first voltage;
• i. second switching means responsive to said first control signal for,
• i. coupling said second terminal to said first supply voltage conductor and
• ii. coupling said first terminal to said second supply voltage conductor
• if said third voltage is less than said second voltage;
• and
• j. first temperature indicating means responsive to said first temperature sensing means for producing a perceivable indication of said actual temperature.