Abstract: Circuitry for controlling the temperature of a thermoelectric environmental chamber includes a pair of digital switches for selecting any desired temperature between -10 degrees C. +79 degrees C., the digital slide switches selecting tap points of a group of series connected resistors forming a feedback loop of an operational amplifier. Three resistors connected in series with the output of the operational amplifier and the feedback resistors produce a plurality of voltages that represent upper and lower limits to tolerance range about the selected desired temperature. These voltages are compared by means of a plurality of comparators to a voltage produced in response to a solid state temperature sensor located in the thermal compartment of the environmental chamber. Decoding circuitry decodes the outputs of the comparators to produce signals which control switching devices that control the direction of current through a thermoelectric heat pumping device.

Abstract: A portable, lightweight thermoelectric environmental chamber includes insulative side walls, an insulative bottom and an insulative cover that is hingeably connected to one of the walls. A handle is attached to the upper surface of the cover. A thermoelectric unit includes a thermoelectric heat pumping device disposed between an internal heat exchanger disposed inside the thermal compartment of the environmental chamber and an external heat exchanger disposed outside of the thermal compartment. An external blower continuously forces outside air along the surface of the external heat exchanger when the thermoelectric environmental chamber is turned on. An internal blower is controlled by a momentary switch that turns the internal blower on when the cover is closed. A shroud encloses the internal blower and guides air in close proximity to the internal heat exchanger and recirculates air in the compartment to maintain a uniform temperature in the thermal compartment when the cover is closed.

Abstract: A compact thermoelectric refrigerator includes a storage compartment, the lower portion of which is lined with a thin, high-conductivity aluminum liner which functions as an internal heat exchanger. The storage compartment is separated by means of a dividing wall from a compartment containing a thermoelectric module, a low profile, high density external heat exchanger including an extruded high thermal conductivity aluminum base and a plurality of closely spaced high thermal conductivity fins attached to the base by means of thermal epoxy, and a centrifugal fan disposed above the external heat exchanger and driven by a fan motor disposed in a recess in a wall of the thermoelectric refrigerator. Outside air is drawn by the centrifugal fan through an air intake grill located in the upper portion of an end panel and is forced through the fins of the external heat exchanger and out of an air outlet grill located along the lower edge of the end panel.

Abstract: A portable cooler includes a urethane foam shell having a storage compartment and fan recess. An internal heat exchanger is mounted to a wall of the storage compartment and conducts heat out of the storage compartment by means of a thermally conductive block to an external heat exchanger mounted in the fan recess. An electric fan mounted in the fan recess blows outside air through fins of the external heat exchanger. A grill covers the fan recess. A solid state thermoelectric device is disposed between the external heat exchanger and the thermally conductive block. A control circuit includes a first thermistor which senses the temperature of the internal heat exchanger. A comparator having one input coupled to a temperature control reostat and another input coupled to the first thermistor controls a switch circuit which connects the terminals of the thermoelectric device and the terminals of the fan motor to a supply voltage conductor.