Grain bin aeration control

Claim 2

Grain bin aeration control apparatus comprising: temperature sensor means positionable in a bin for exposure to the temperature therein; an air mover; control circuit means having input means for a source of electrical energy and output means connected to said air mover and including switching means; said temperature sensor means including a plurality of temperature responsive resistors positionable at various locations in a bin; said control circuit means including a plurality of bridges, each bridge of said plurality having one of said resistors in an arm thereof; said control circuit means including a plurality of unbalance detector means, each detector means of said plurality being connected to one of said bridges of said plurality; and said switching means being coupled to all of said detector means and operable by each of said detector means upon detection of an unbalanced condition in its respective bridge to couple said source to said air mover.

Claim 3

The apparatus of claim 1 wherein; each of said bridges has two arms in common, with a variable resistor in one said arms to establish a reference voltage for all of said bridges, said variable resistor being manually variable to establish the level of said reference voltage as desired to correspond to a temperature level sought at said sensor means.

Claim 4

The apparatus of claim 2 wherein each of said unbalance detector means includes: a first normally-quiescent transistor having its control circuit path connected across a series combination of the temperature responsive resistor of its respective bridge and the said variable resistor and oriented to become conductive upon occurrence of a voltage drop of a predetermined amount in one polarity across said combination; a second normally-quiescent transistor having its control circuit path connected across the said series combination and oriented to become conductive upon occurrence of a voltage drop of a predetermined amount in an opposite polarity across said combination; and the total range of the two of said voltage drops being selected to correspond to the desired range between the high and low temperatures sensed by said temperature responsive resistors at which air mover operation is desired for any one setting of said variable resistor.

Claim 5

The apparatus of claim 3 wherein; each of said transistors of said pair requires between 0.45 and 0.8 volts base-emitter forward bias to be switched from a quiescent state to a conducting state.

Claim 6

The apparatus of claim 1 wherein: said sensor means include probes insertable separately through walls of a bin, each probe having one of said temperature responsive resistors therein and a cable coupled therefrom to the exterior of the bin; said apparatus including a housing mountable on the bin, said housing having a socket portion of said output means therein receiving a plug connected to said air mover, said socket portion being coupled to said input means by said switching means upon operation of said switching means for energization of said air mover; and said probe cables being plugged into said housing for connection to arms of their respective bridges inside said housing.

Claim 7

Grain bin aeration control apparatus comprising: temperature sensor means positionable in a bin for exposure to the temperature therein; an air mover; control circuit means having input means for a source of electrical energy, and output means connected to said air mover, said control circuit means including portion of said sensor means and responsive to a temperature change of a predetermined amount at said sensor means portion to couple said source to said air mover; said circuit means including, a first bridge having a first arm with a temperature responsive resistance (21A) therein, a second arm with a first resistance (76) therein, a third arm with a second resistance (77) therein, and a fourth arm with an adjustable resistance (78,79) therein; first solid state switch means (83) having a control circuit coupled to the junction (86) between said temperature responsive resistance and said first resistance and to the junction (87) between said second resistance and said adjustable resistance, said switch means being switchable in response to a predetermined amount of unbalance in said bridge, said output means including electrically operable line switch means (66,67) having control means (92) coupled to said solid state switch means (83) and operable tHereby, said circuit means further including a second bridge having a first arm with another temperature responsive resistance (22A) therein, a second arm with another resistance (96) therein, a third arm in common with said third arm of said first bridge and, a fourth arm in common with said fourth arm of said first bridge; second solid state switch means (20) having a control circuit coupled to a junction (99) between said another temperature responsive resistance and said another resistance of said second arm of said second bridge, and to the junction (87) between said third and fourth arms of said first bridge; said second control means being switchable in response to a predetermined amount of unbalance in said bridge, and said control means (92) of said line switch means being coupled to said second solid state switch means (20) and operable thereby.

Claim 8

Grain bin aeration control apparatus comprising: temperature sensor means positionable in a bin for exposure to the temperature therein; an air mover; control circuit means having input means for a source of electrical energy, and output means connected to said air mover, said control circuit means including portion of said sensor means and responsive to a temperature change of a predetermined amount at said sensor means portion to couple said source to said air mover; said circuit means including, a first bridge having a first arm with a temperature responsive resistance (21A) therein, a second arm with a first resistance (76) therein, a third arm with a second resistance (77) therein, and a fourth arm with an adjustable resistance (78,79) therein; first solid state switch means (83) having a control circuit coupled to the junction (86) between said temperature responsive resistance and said first resistance and to the junction (87) between said second resistance and said adjustable resistance, said switch means being switchable in response to a predetermined amount of unbalance in said bridge, said output means including electrically operable line switch means (66,67) having control means (92) coupled to said solid state switch means (83) and operable tHereby, said circuit means further including a second bridge having a first arm with another temperature responsive resistance (22A) therein, a second arm with another resistance (96) therein, a third arm in common with said third arm of said first bridge and, a fourth arm in common with said fourth arm of said first bridge; second solid state switch means (20) having a control circuit coupled to a junction (99) between said another temperature responsive resistance and said another resistance of said second arm of said second bridge, and to the junction (87) between said third and fourth arms of said first bridge; said second control means being switchable in response to a predetermined amount of unbalance in said bridge, and said control means (92) of said line switch means being coupled to said second solid state switch means (20) and operable thereby.

Claim 9

The apparatus of claim 6 and further comprising: additional bridges, each having first and second arms with temperature responsive resistances and other resistances, respectively, therein and each having third and fourth arms in common with the third and fourth arms, respectively, of said first bridge; additional solid state switch means corresponding in number to the number of additional bridges, each additional solid state switch means having a control circuit coupled to the junction between the first and second arm of its respective bridge and to the junction between said third and fourth arms of said first bridge.