A device for detecting a level of a material in a bin or hopper and turning on or off a motor to control feeding of said material into said bin or hopper which in turn controls said level of said material within a preselected full point and a preselected refill point, said device comprising:
- (a) a first electronic force sensitive resistor located at said full point for detecting a force of said material, a first electronic circuit means responsive to the detected force for turning off said motor thereby stopping said material from overflowing of the bin, said circuit means comprising:
- a first logic nor gate connected to said first force sensitive resistor located at said full point of said bin so that when the resistance of first resistor is low a output of said first nor gate is high;
- a first type D flip flop with a reset input of said flip flop connected to the output of said first nor gate so that when said output of said first nor gate is at a logic high an output of said first flip flop is reset to a logic low;
- an enhancement mode, N-channel MOSFET switch with a gate of said MOSFET switch connected to the output of said first flip flop so that when said first flip flop is reset said MOSFET switch is in a non-conducting mode;
- an optical coupler with an input LED in electrical series with said MOSFET switch such that when said MOSFET switch is in the non-conducting mode said optical coupler is also in a non-conducting mode and an output section of said optical coupler is in the non-conducting mode;
- a triac switch with a gate connected to the output of said optical coupler so that when said output of said optical coupler is in the non-conducting mode said triac switch is also in the non-conducting mode;
- said triac switch is connected in electrical series with said motor so that when said triac switch is in the non-conducting mode said motor is off and said material is stopped from overfilling said bin;
- and
- (b) a second electronic force sensitive resistor located at said refill point within said bin for detecting a force of said material, a second electronic circuit means responsive to a detected force for turning on said motor thereby refilling said bin with said material, said circuit means having:
- a second logic nor gate connected to said second force sensitive resistor located at said refill point of said bin so that when the resistance of said second resistor is high a output of said second nor gate is low;
- a third logic nor gate connected so that when an input of said third nor gate is a logic low, an output of said third nor gate is a logic high;
- a second type D flip flop with a set input of said second flip flop connected to the output of said third nor gate so that when said output of said third nor gate goes to a logic high an output of said second flip flop is set to a logic high;
- said first flip flop with a set input of said first flip flop connected to the output of said second flip flop so that when said output of said second flip flop goes to a logic high the output of said first flip flop is set to a logic high;
- said MOSFET switch with the gate of said MOSFET switch connected to the output of said first flip flop so that when the output of said first flip is set said MOSFET switch is in a conducting mode;
- said optical coupler with the input LED of said optical coupler in electrical series with said MOSFET switch such that when said MOSFET switch is in a conducting mode said LED is also in a conducting mode and the output section of said optical coupler is in the conducting mode;
- said triac switch with the gate connected to the output of said optical coupler so that when said output of said optical coupler is in the conducting mode said triac switch is also in the conducting mode;
- said triac switch connected in electrical series with said motor so that when said triac switch is in the conducting mode said motor is on and said material is allowed to fill said bin.