Marlow Industries, Inc.

Robert L Montgomery

John L Nelson

Richard J Buist

Alternating current is applied to a bi-directional triode thyristor (triac) and a zero voltage switch, the zero voltage switch controls the operation of the triac to selectively heat a heater element, the thermal energy of the heater element drives a first thermoelectric heat pump (module), acting as a dc power generator, to produce power to drive a second thermoelectric heat pump acting as a cooling or heating source, towards a preselected temperature, a thermally sensitive resistor (thermistor) senses the temperature and generates a resistance corresponding to the temperature, the thermistor is connected to the zero voltage switch in series with a temperature set point resistor (potentiometer) and source of power to form a voltage divider input to the zero voltage switch, whereby when the resistance of the thermistor substantially equals that of the temperature set point resistor the zero voltage switch inhibits the trigger pulses to the triac to cut off ac current to the heater element.

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Garland, TX, United States of America

Robert L Montgomery