Integrated level sensing printed circuit board

• US 9,692,411 B2
• Filed: 05/13/2011
• Issued: 06/27/2017
• Est. Priority Date: 05/13/2011
• Status: Active Grant

• Current Assignee: Xylem Ip Holdings LLC (Xylem, Inc.)
• Original Assignee: Flow Control LLC (Xylem, Inc.)
• Inventors: Estrada, Jesus
• Primary Examiner(s): Ngon, Ricky
• Application Number:
  US13/107,584
• Publication Number:
  US 20120290227A1
• Time in Patent Office: 2,237 Days
• Field of Search: 702 55, 702 52, 73290 R, 73304 C, 324696, 324691
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

A level sensing circuit board featuring at least one processor and at least one memory including computer program code, where the at least one memory and computer program code are configured, with the at least one processor, to cause the apparatus at least to: respond to a signal containing information related to the electrical conductivity of a material causing a stimulus to a sensing plate that corresponds to a positive plate of a capacitor directly connected to an input of a comparator that forms part of a variable frequency oscillator; and determine a proportional response containing information about the material causing the stimulus to the sensing plate based at least partly on the signal received. The level sensing circuit may be used as a means to turn a pump on or off based on a sensed fluid level.

Claims

1. A level sensing printed circuit board, comprising:

a sensing capacitor having a sensing plate and a negative plate, the sensing plate being a positive plate and configured to sense the electrical conductivity of a material causing a stimulus and provide positive plate signaling containing information about the electrical conductivity sensed, and the negative plate corresponding to a ground plane of the level sensing printed circuit board;

a variable frequency oscillator having a comparator with an input configured to respond to the positive plate signaling, and provide variable frequency oscillator signaling containing information about variable frequency oscillations based upon the positive plate signaling sensed; and

a signal processing module configured at least to;

respond to the variable frequency oscillator signaling, and

determine a corresponding signal containing information about a proportional frequency response caused by the stimulus and sensed by the sensing plate, based at least partly on the variable frequency oscillator signaling received.

2. A level sensing printed circuit board according to claim 1, wherein the variable frequency oscillator signaling received contains information about a frequency variation that is proportional to the electrical conductivity of the material placed in front of the sensing plate, how much of the sensing plate'"'"'s surface the material is facing, and the distance between the material and the sensing plate.

3. A level sensing printed circuit board according to claim 1, wherein the proportional frequency response contains information about at least one of the following:

the type of material in the proximity of the sensing plate;

or

the distance between the material and sensing plate;

or

the size of the material'"'"'s surface facing the sensing plate;

or

some combination thereof.

4. A level sensing printed circuit board according to claim 1, wherein the ground plane is configured to surround the sensing plate laterally and from behind to act as a barrier that nullifies the response from the sensing plate and cause the sensing plate to detect objects placed substantially in front of it.

5. A level sensing printed circuit board according to claim 1, wherein the signal processing module is configured to implement signal processing functionality related to implementations configured related to multiple sensing plates based at least partly on one input.

6. A level sensing printed circuit board according to claim 1, wherein the signal processing module is configured to distinguish between material types, so as to determine if the material is water or a part of a person in contact with the sensing plate.

7. A level sensing printed circuit board according to claim 1, wherein the signal processing module is configured to detect a non-conductive material, including plastic.

8. A level sensing printed circuit board according to claim 7, wherein the variable frequency oscillator comprises the comparator;

the sensing capacitor is directly connected to an inverting input and ground, an output and the inverting input are connected through a resistor (RY);

the non-inverting input is connected through three resistors, all having substantially the same value (RXa, RXb, RXc), to power (+V), ground and the comparator'"'"'s output; and

the comparator output is used as feedback for both inputs.

9. A level sensing printed circuit board according to claim 7, wherein the comparator is configured to operate as follows:

when the comparator output is high, it generates a current that charges the sensing capacitor connected to the inverting input and a reference voltage applied to the non-inverting input, the value of the reference voltage is higher than the sensing capacitor'"'"'s voltage when the comparator'"'"'s output changes from low to high, as a result, the comparator output remains high until the sensing capacitor voltage reaches the reference voltage, at which point the comparator output changes from high to low;

the low state generates a current that discharges the sensing capacitor connected to the inverting input and a different value for the reference voltage applied to the non-inverting input, the value of the reference voltage is lower than the sensing capacitor'"'"'s voltage when the comparator'"'"'s output changes from high to low, as a result, the comparator'"'"'s output remains low until the sensing capacitor'"'"'s voltage reaches the reference voltage, then the comparator'"'"'s output changes from low to high and the cycle starts again.

10. A level sensing printed circuit board according to claim 1, wherein the signal processing module is configured to provide the corresponding signal as an output signal for turning on or off a pump based on a fluid level.

11. A level sensing printed circuit board according to claim 1, wherein the sensing capacitor is built using conductive strokes on the level sensing printed circuit board, comprising the variable frequency oscillator that provides the variable frequency oscillator signaling, and the signal processor module forms part of a microcontroller that comprises at least one memory and computer program code and at least one processor configured to perform the signal processing functionality for responding to the variable frequency oscillator signaling and determining the corresponding signal.

12. A level sensing printed circuit board according to claim 1, wherein the input is an inverting input of the comparator.

13. A level sensing printed circuit board according to claim 12, wherein the sensing capacitor is a stand alone capacitor coupled directly or indirectly to the level sensing printed circuit board, and the negative plate of the sensing capacitor is directly connected to the ground plane of the level sensing printed circuit board.

14. A level sensing printed circuit board according to claim 1, wherein the proportional frequency response is based at least partly on a change in a relationship between a value of the sensing capacitor and a frequency of the variable frequency oscillator.

15. A level sensing printed circuit board according to claim 1, wherein the signal processor module is configured to count pulses produced by the variable frequency oscillator during a constant time interval or time base, so the proximity of any material to the sensing plate is reflected as a reduction in the pulses counted so as to detect the material.

16. A level sensing printed circuit board according to claim 1, wherein the signal processing module is configured to detect the distance between the sensing plate and the material based at least partly on the fact that, if the type of material doesn'"'"'t change, and the amount of sensing plate'"'"'s surface facing the material remains substantially constant, then the frequency variation of a variable frequency oscillator coupled to the sensing plate will be inversely proportional to the distance between the material and the sensing plate.

17. A level sensing printed circuit board according to claim 1, wherein the signal processing module is configured to detect a fluid level and the size of a flat object facing the sensor plate based at least partly on the fact that, if the type of material doesn'"'"'t change, and the distance between the material and the sensing plate remains substantially constant, then the frequency variation in a variable frequency oscillator coupled to the sensing plate is directly proportional to the amount of sensing plate'"'"'s surface facing the material.

18. A level sensing printed circuit board according to claim 1, wherein the signal processing module is configured to detect different types of materials based at least partly on the fact that, if the distance between the material and the sensing plate remains substantially constant as well as the amount of sensing plate'"'"'s surface facing the material, then the frequency change of a variable frequency oscillator coupled to the sensing plate will be directly proportional to the electrical conductivity of the material.

19. A level sensing printed circuit board according to claim 1, wherein the sensing plate is segmented into several discrete surfaces, each one with a well defined contribution to the net capacitance value but all them interconnected in a different printed circuit board layer, so that only one sensing plate can act as multiple virtual sensor surfaces, and so that the sensing plate need not be located on the same printed circuit board layer as the signal processing module and the variable frequency oscillator.

20. A level sensing printed circuit board according to claim 1, wherein the signal is provided from an output of the variable frequency oscillator.

21. A level sensing printed circuit board according to claim 1, wherein the signal processing module comprises:

at least one processor;

at least one memory including computer program code;

the at least one memory and computer program code configured to, with at least one processor, cause the signal processing module to implement the signal processing functionality for responding to the signal and determining the corresponding signal.

22. A level sensing printed circuit board according to claim 1, wherein the sensing capacitor forms part of the level sensing printed circuit board, and the negative plate of the sensing capacitor is directly connected to the ground plane of the level sensing printed circuit board.

23. A level sensing printed circuit board, comprising:

a variable frequency oscillator having a comparator with an inverting input, a non-inverting input and an output, having a sensing capacitor with a positive plate and a negative plate, and having resistors;

a sensing plate that corresponds to the positive plate of the sensing capacitor directly connected to the inverting input of the comparator of the variable frequency oscillator, and the negative plate of the sensing capacitor corresponding to a ground plane of the level sensing printed circuit board; and

a signal processing module configured at least to;

respond to a signal containing information about the electrical conductivity of a material causing a stimulus sensed by the sensing plate,

determine a corresponding signal containing information about a proportional frequency response caused by the stimulus and sensed by the sensing plate, based at least partly on the signal received, and

provide the corresponding signal as an output signal containing information about the proportional frequency response for turning on or off a pump.

24. A level sensing printed circuit board according to claim 23, wherein the level sensing printed circuit board comprises a ground plate that surrounds the sensing plate laterally and from behind.

25. A level sensing printed circuit board according to claim 23, wherein the signal contains information about a frequency variation that is proportional to the electrical conductivity of the material placed in front of the sensing plate, how much of the sensing plate'"'"'s surface the material is facing, and the distance between the material and the sensing plate.

26. A level sensing printed circuit board according to claim 23, wherein the proportional frequency response contains information about at least one of the following:

the type of material in the proximity of the sensing plate;

or

the distance between the material and sensing plate;

or

the size of the material'"'"'s surface facing the sensing plate.

27. A level sensing printed circuit board according to claim 23, wherein the signal processing module comprises:

at least one processor; and

at least one memory including computer program code;

the at least one memory and computer program code configured to, with at least one processor, cause the signal processing module to implement the signal processing functionality for responding to the signal, determining the corresponding signal, and provide the corresponding signal as the output signal.

28. A level sensing printed circuit board according to claim 23, wherein

the positive plate is coupled to the inverting input;

and

the resistors comprise a first resistor coupled between the inverting input and the output, a second resistor coupled between the non-inverting input and the output;

a third resistor coupled between a voltage source of the level sensing printed circuit board and the non-inverting input, and a fourth resistor coupled between the non-inverting input and the ground plate of the level sensing printed circuit board.

29. A pump, comprising:

a pump controller, configured to respond to a control signal and turn the pump on or off; and

a level sensing printed circuit board having

a sensing capacitor having a sensing plate and a negative plate, the sensing plate being a positive plate and configured to sense the electrical conductivity of a material causing a stimulus and provide positive plate signaling, and the negative plate corresponding to a ground plane of the level sensing printed circuit board,

a variable frequency oscillator having a comparator with an input configured to respond to the positive plate signaling, and provide variable frequency oscillator signaling containing information about variable frequency oscillations, based upon the positive plate signaling received, and

a signal processing module configured at least to;

respond to the variable frequency oscillator signaling,

determine a corresponding signal containing information about a proportional frequency response caused by the stimulus and sensed by the sensing plate, based at least partly on the signal received, and

provide the corresponding signal as the control signal containing information about the proportional frequency response for turning on or off a pump.

30. A pump according to claim 29, wherein the signal processing module comprises:

at least one processor; and

at least one memory including computer program code;

the at least one memory and computer program code configured to, with at least one processor, cause the signal processing module to implement the signal processing functionality for responding to the signal and determining the corresponding signal.