GB2517172A

GB2517172A - Fixed sensor device for automatic monitoring of moisture content in building materials

Info

Publication number: GB2517172A
Application number: GB1314495.1A
Authority: GB
Inventors: Mohammed Iftkhar; Paolo Di Prodi
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-08-13
Filing date: 2013-08-13
Publication date: 2015-02-18
Anticipated expiration: 2033-08-13
Also published as: GB201314495D0; GB2517172B

Abstract

A moisture detection sensor comprises a couple of conductive probes and, a water resistant enclosure 9 containing a micro controller unit 4 or equivalent logic circuit connected to the probes, a coin battery 7 and a colour LED 8. The sensor may be used in a building structure to detect moisture penetration and may include two fish hook nails 6 to secure the sensor in position. Alternatively the probes themselves may be hook shaped. The enclosure may be colour coded for use of the sensor with different materials and the controller may contain calibrated look up tables for the material types. Pre-calculated wake up periods may be used to extend battery life and a tamper proof spinning cap can aid against it being dislodged from its measurement location. The sensor may act as an automated alert system including a radio frequency transmitter.

Description

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to the detection of water penetration into residential and commercial buildings via a low cost fully automated a'ert sensor.

BACKGROUND

This novel device is the culmination of 28 years of research into microbiology associated to watcr damage through psychrornctry implemented with currcnt sensing technology.

Modern homes and businesses have indoor plumbing, porous finishings and materials. This combination creates an ideal environment for water and humidity damage.

The source and potential threat of water and humidity damage to buildings is not limited only to structural leaks, rising rivers, coastal flooding, frozen pipes, defective or faulty appliances, defective fixtures such as a stuck toilet float.

Faulty or damaged construction for instance, newly installed drainage systems may fail after first heavy rains.

Fire control practices can cause water damage to areas of the building after having extinguished fires.

High ambient humidity can cause moisture damage -due to hygroscopic material seeking moisture equilibrium with the environment -undetected and left untreated in environmental conditions exceeding 60% RI-I (relative humidity) thus having the potential to become mildewed.

in essence, any time a structure becomes wet the potential for health hazards rise significantly. Dormant fungi, spores germinate, bacteria begin to multiply and viruses become more active. People with allergies are first to experience the negative effects of the increased evels of bacteria and fungi followed by infants and the elderly.

Responding to wet materials is crucial in an effort to address the risk of sick building syndrome (SBS). One of the causes of SBS is associated with incomplete drying of water damaged structures and contents, leading to degradation of indoor air quality. As described earlier bacteria, fungi and viruses become hyperactive in this moist environment.

Consequently micro organisms multiply. hence the air quality deteriorates leading to the building becoming sick and uninhabitable. In these instances our early warning detection devices can help to prevent not only health risks but also the inevitable major repairs due to incomplete drying.

Considering that pathogens and allergens are harmful to human health and that threat is prevalent as water flows through structures -often canying a variety of pathogens and allergens derived from water intrusion-with the likelihood exacerbated in cases of water containing organic material, structures that have been effected become damp and ideal supporting grounds for microbiological amplification.

I

Whilst these facts alone clearly outline that an early alert, and monitoring system is needed to combat a variety of potential threats that exist particularly in cases of incomplete drying of water damaged structures and contents.

This is not a conclusive application of this unique and fully automated invention, in fact the unique design features with integrated components encased in an impermeable to gas and moisture housing serves as a multipurpose application.

SUMMARY

According to one aspect of the present invention there is provided a moisture detection sensor comprising: a couple of conductive probes or nails, a plastic water resistant enclosure containing a micro controller unit MCU or equivalent logic circuit connected to the two conductive probes, a coincell 3V rechargeable or non-rechargeable battery and a colored single LED or an array of LEDs.

The conductive probes are connected to the MCU that applies a voltage across the two conductors and monitors the current passing between them. The voltage is periodically reversed to avoid metal oxidation of the conductive nails due to electrolysis.

The MCU wakes up periodically to measure the current intensity passing in the material and in case of a single LED modulates the brightness via a PWM signal to indicate the level of moisture in the material in such a way that a non lit LED indicates no moisture given that PWM has 0% duty cycle and totally lit LED indicates saturated moisture given that the PWM has a 100% duty cycle.

In the case of an array of LEDS the MCJJ will lit a number of LED proportional to the moisture content, for example with an array of 10 LEDS supposing the moisture content is between 0 and 10 % only one LED will be on, when the moisture content is between 11% to 20% two LEDs will be on and so on.

The MCU contains in memory typically ERPROM a look up taHe composed of a series of value pairs < I, M> where I indicates a current measured in mA units and M measure the moisture level of the specific material ranging from 0 to 100.

A typical lookup table contains 100 data points whose values depends on the particular material such as wood.

Every lookup table for each material is pre-calculated in controlled experiments and is stored in each moisture sensor at production time.

The thokup table is implemented in the MCU as a dictionary data structure containing as keys the current I (mA) readings and as values the moisture values.

The period of wake up of the CPU is dependent on the moisture content and implemented as a dictionary data structure containing as keys the M (%) moisture values and as values the wake up period expressed in seconds: the higher the moisture content the shorter the wake up period and viceversa.

The minimum wake up period is set to 1 hour which is 3600 seconds and is set to a maximum of 2 seconds when the material is saturated reaching a maximum moisture content of 100%.

This approach minimizes power consumption thus allowing the moisture sensor to run on a single coincell battery for more than one year.

The MCU calculates the current 1(t) at each wake up cycle by applying a voltage difference Vbatt across the two probes; measuring the voltage via the ADC and then calculating the current 10) via the Ohm law.

The voltage difference is reversed at each wake up reading to avoid metal oxidation of the pins.

According to a further aspect of the present invention, there is provided a method of resetting the MCU status via a capacitive switch, a magnetic reed switch or a piezo electric switch. The reset is triggered via an interrupt pin of MCU to wake up the MCU the first time is installed in the surface or to reset to factory in case required.

The first time the pin is installed the human operator will exert a vertical pressure on the top surface pushing the sensor into the wall and once releasing it, triggering the reset interrupt will activate the MCU for operation.

If the reset is triggered a second time as a resuli of perhaps moving the sensor into another surface the MCU will simp'y reset its parameters to factory settings.

According to a further aspect of the present invention, it is possible to add an RE TX module connected to the MCU to wirdessly transmit the moisture data to a central RE RX station for data collection.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate exemplary embodiments of the present invention: Figure 1 is an exploded sectional view along the vertical axis of the moisture pin Figure 2 is a top view of the moisture pin showing the top PCB layer with a single LED configuration Figure 3 is a top view of the moisture pin showing the top PCB layer with a an array of LEDs Figure 4 shows a typical placement of the moisture pin into a wall sectioned isometrically Figure 5 shows a the two lookup tables containing the current to moisture levels and the moisture levels to wake up periods Figure 7 contains a typical electronic implementation of the AC current measurement and interaction with the single LED case

DETAILED DESCRIPTION

Referring to the accompanying drawings, and particularly Figures 1 and 2, there is illustrated a moisture sensor pin.

The moisture pin is composed by two main plastic components, the core 9 which does not rotate contains two PCB 4,10 and batteries 7 connected to the two fish hook probes 6. Each fish hook probe is coated with a non conductive material shown in 5. The top PCB 10 contains the MCU and required passive components as well a single or an array of colour LED 8.

The non-conductive film 5 prevents false readings from the surface of the wall that typically contains paint or plaster.

The fish-hooks can also be used solely for the purpose of affixing the pin into the wall and providing extra two pins for the sake of measure the conductance of the material.

The outer screw cap is a single moulded piece comprising the plastic components 1,2,3 where 2 is a depressed surface that facilitate the insertion in the surface via the operator's thumb.

The outer screw cap rotates in both directions (clockwise and anti-clockwise) around the main core by means of a mechanical ridge.

The MCU optionally can be connected to a reset switch 14 that can be implemented as a piezo-element, a reed magnetic switch or a mechanical switch.

The MCU optionally can be connected to an RF component 16 via a tuned antenna 15 used to transmit a packet containing a sensor identification number and the last measured moisture level to a central receiving station for remote monitoring.

The transmit intervah for the RE packets are synchronized with the wake up period of the MCU transmitting a packet after each wakeup cycle.

Figure 3 illustrates a variation of the sensor shown in Figure 2 that contains an array of LEDs that will be activated by the MCU in a counter-clockwise or clockwise manner to show the user the percentage of moisture starting from the LED 20 when moisture is for example less than 10% until all LEDs 21 are activated when the moisture reaches 100 %.

The screw cap enclosure can be of a translucent material to provide a clear reading, avoiding confusion arising from the plastic colour case of LEDs.

Figure 4 explains how the sensor is positioned in a typical house showing a wall composed of two pasterboards 22 and 23 spaced by an empty cavity 24. The sensor will typically be placed within 20 cm from the floor 25 to avoid making contact with the wood timber axis usually present at that level.

Figure 5 contains the two lookup tables that the MCU uses for estimating the moisture content M 27 from the measure current 26 and then selecting the wakeup period 31 to minimize power consumption.

The first lookup table contains inclusive intervals for example the first measured entry 28 means that until when current is 1 mA the moisture content 29 is 0%, when the current is more than 9OmA the moisture content is 100%.

From the moisture content the MCU then calculates the wake up period with the second look up table with the same manner: when the moisture content 32 is less than 3 % then the wakeup period 33 TP is 3600 seconds and when the moisture content is 100 then the wake up period is 2 seconds.

Figure 6 details a simple electronic implementation of the moisture pin whereby the MCU is connected as follow: two digital output pins 101 38, 102 39 are connected to the conductive probes 34,35 and feedback into an anaogic input A0 pin 37 that measure the voltage drop across the resistor 36 R. The MCU is powered by the battery via VCC 42 at +3.OV and grounded to GND 43 to the negative of the battery.

Other output digital pins of the MCU such as 103 in 41 are connected to one or more LEDs to show the moisture evel. In the case of only one LED the moisture content is mapped into a single PWM channd that goes from 0% to 100%. In the case of multiple LEDS the pins 103,104,105 etc will enable the LEDs via a shift register for example with 10 outputs the moisture level is quantized as increments of 10%, with 4 outputs with 25% and so on.

The MCU can be reset via an interrupt pin 40 connected to either a mechanical switch, a magnetic reed switch or a piezo-element with the corresponding signal conditioning not drawn in the figure.

When the reset pin is pulled down to GND, the MCU resets to its initial state described in 44.

The MCU then runs the firmware which is summarized in figure 7 where the initial state entered on power up or rest is 45.

The first state is then to sleep by the initial state period TP in 46. Once the watchdog triggers a wakeup event in 47, the MCi exits his low power mode and sets is digital pins in 48 to high and low, does a voltage measurement from pin A0 and then reverses the polarity in 49 by inverting the pins levels. It then sets both pins to low to prevent any current sinks in the material that would consume battery power. In 50 the MCU fetches the moisture content from the first lookup table, then sets the PWM level SI in the case of one LED output via pin 103 and finally computes the wake up period 52. After that the MCIJ sleeps again by TP back to state 46.

If an interrupt is triggered by the user via the mechanism described in 40, the MCU resets its state to 44 and the entire program flow starts again.

Acronyms END: light emiaing diode typically red green or blue phosphor MCU: micro controller unit typically a low power controller 8/16/32 hit with digital and analog 10 Lipo: Lithium Polymer battery a type of rechargeable battery PWM: a modulation technique used to regulate the light intensity of an LED Impedance: an electric measure that is a complex number related to resistance Conductance: similar to Impedance PCB: printed circuit board EI-PR(I)M: read/write internal memory of an MCU

S

Claims

ClaimsEMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR

PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS: 1. According to one aspect of the present invention there is provided a moisture detection sensor comprising: a couple of conductive probes and optiona'ly two fish hooks nails, a water resistant enclosure containing a micro controller unit MCU or equivalent logic circuit connected to the two conductive probes, a coin 3V rechargeable or non-rechargeable battery and a colour LED
2. A sensor according to Claim I wherein the p'astic enclosure is colour coded for different materials.
3. A sensor according to Claim I or 2 wherein the MCU contains calibrated lookup tables for each material type coded in corresponding colours
4. A sensor according to Claim 1,2,3 that maximizes battery duration with pre-caiculated wakeup periods for each material type
5. A sensor according to any one of Claims I to 4 wherein each of the probes are shaped 111cc fish hooks -measuring at least 12mm corresponding to the average thickness of a plasterboard -to minimise the probability of the device oosing itself from the applied surface
6. A sensor according to any one of Claims 1 to 5 where the fish hook contains a springy termination of extra 2mm allowing the pin to open after insertion 7. A sensor according to any one of Claims 1 to 6 where the tensile steel fabrication of the fish hook pin inserts allows for the hook part to memorise the extended position, thus facilitating insertion into the surface and the automatic opening of the hook once passed the 12mm mark.8. A sensor according to any one of Claims ito 7 where the fish hooks are placed so that the outward pins are opposing to each other for the purpose of using a wider surface area to hold and bare the outward force needed to extract the pin 9. A sensor according to any one of Claims I to 8 with a unique and novel feature: the tamper proof spinning cap, which will prevent accidental twisting of the device whilst in its fixed position on the proposed monitoring surface, reducing the threat of the moisture detector pins and the fish hooks from snapping off.10. A sensor according to any one of Claims I to 9 enclosed in a single moulded, water and vapour proof enclosure with minimum rating 1P67 that prevents water vapour ingress and surface condensation to prevent false readings 11. A sensor according to any one of Claims 1 to 10 whose enclosure will not allow salts to leak into the electronics causing malfunction of electrics components.12. A sensor according to any one of Claims 1 to 11 with tamper proof enclosure that contains a tamper seal indicator 13. A sensor according to any one of Claims ito 12 enclosed in an anti-shock enclosure resistant to vertical forces 14. A sensor according to any one of Cairns I to 13 with a shatter proof material for the enclosure for child and user friendly qualities 15. A sensor according to any one of Claims I to 14 which might contain a capacitive switch to reset the MCU to factory settings 16. A sensor according to any one of Claims ito 14 which might contain a reed switch to reset the MCU to factory settings 17. A sensor according to any one of Claims 1 toi4 which might contain a piezo electric element to reset the MCU to factory settings 18. A sensor according to any one of Claims 1 to 14 including an RF transmitter to remotely transfer the moisture level to a receiving unit that can be a mobile smart phone or a desktop computer.19. A sensor according to any one of Claims I to 14 using an array of LEDs to shows to the user a progressive indication of the moisture content 20. A sensor according to any one of Claims I to 19 that sits in situ, directly on the surface that needs to be monitored continuously.21. A sensor according to any one of Claims I to 19 which is low cost and disposable 22. A sensor according to any one of Claims I to 19 which acts as automated alert system for moisture detection 23. A sensor according to any one of Claims I to 19 which determines moisture via precise current measurements from a calibrated scale and that does not deteriorate in time via electrolysisBAmendments to the claims have been made as follows: Claims 1. A moisture detection sensor comprising: a couple of conductive probes, a water resistant enclosure containing a micro controller unit MCU or equivalent logic circuit connected to the two conductive probes, a coin cell non-rechargeable battery and a colour LED, a tamper proof spinning cap, which will prevent accidental twisting of the device whilst in its fixed position on the proposed monitoring surface, reducing the threat of the moisture detector pins from snapping off.2. A sensor according to Claim 1 that maximizes battery duration with pre-calculated wakeup periods for different material type of surface to be monitored.3. A sensor according to any one of Claims 1,2 wherein two additional nails shaped like fish *:** hooks can be added, measuring at least 12mm corresponding to the average thickness of a plasterboard to minimise the probability of the device loosing itself from the applied surface.*.....* 4. A sensor according to Claim 3 where the fish hook contains a springy termination of extra 2mm allowing the pin to open after insertion. 0**5. A sensor according to Claim 4 where the tensile steel fabrication of the fish hook pin inserts allows for the hook part to memorise the extended position, thus facilitating insertion : .°. into the surface and the automatic opening of the hook once passed the 12mm mark.* 6. A sensor according to any one of Claims 3 to 5 where the fish hooks are placed so that the outward pins are opposing to each other for the purpose of using a wider surface area to hold and bare the outward force needed to extract the pin.
7. A sensor according to any one of Claims 1 to 6 that is disposable
8. A sensor according to any one of Claims ito 7 that on insertion via human application activate an internal switch that resets the moisture monitoring cycle.