Abstract:
An illuminated doorbell touch pad system is disclosed, having a chime control unit controlled by a micro-processor which continually calibrates according to a process for discriminating between a human touch and moisture, rain and small animals, for changes in capacitance of a metal housing enclosing an outdoor portion of the illuminated doorbell touch pad system.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 61/927,975, filed Jan. 15, 2014, entitled Illuminated Doorbell Touch Pad System, and invented by Donald J. Ladanyi and Georgios V. Lazaridis. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present invention relates in general to doorbell chimes, and in particular to a doorbell chime having a capacitive touch pad system. 
     BACKGROUND OF THE INVENTION 
     Prior are doorbell chimes have been provided using discrete components to provide relays and switching circuits for controlling the doorbell chimes. Some doorbell chimes have been provided with illuminated chime housings also using discrete components. Typically, a control voltage is applied to a doorbell push button switch. Actuating the push button switch applies power to a chime coil which rings the chime. Relay circuits have also been used to apply a control voltage to a relay which results in a power voltage being applied to ring the chime. Touch sensors have also be used for actuating doorbell chime systems, but are often set off by environmental conditions causing false doorbell rings. 
     SUMMARY OF THE INVENTION 
     An illuminated doorbell touch pad system is disclosed, having a chime control unit controlled by a micro-processor which continually calibrates according to a process for discriminating between a human touch and moisture, rain and small animals, for changes in capacitance of a metal housing enclosing an outdoor portion of the illuminated doorbell touch pad system. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying Drawings which show various aspects for an illuminated doorbell touch pad system according to the present invention, as set forth below: 
         FIGS. 1-3  are circuit diagrams; and 
         FIGS. 4-10  are flowcharts showing a process for operating in a microprocessor controlling the system for storing settings in memory and operating the microprocessor to continually calibrate a capacitance of a touch surface to discriminate a human touch from moisture, small animals and other type environmental contacts. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , the wires of the chime button installation are connected at the IN-1 IN-21 terminals of the IDTPS. A Power Supply Unit  2  is responsible to rectify, smooth and regulate the input voltage and provide DC voltage for the microcontroller  3 , the MOSFET AC switch  4  and the illumination LEDs  5 . 
     The touch sensor is based on the Frequency-Change touch sensing technique. The microcontroller&#39;s  3  internal comparator is used to perform a relaxation oscillator with the help of an external RC network  6 . The oscillator oscillates at a pre-determined frequency based on the values of the resistor R and the capacitor C of the RC network. The metallic part of the housing performs the touch electrode (touch pad)  7 . When the touch electrode  7  is touched, the human body capacitance is added in parallel to the capacitor C of the RC network  6  effectively changing the overall capacitance of the RC network. This capacitance change leads to a frequency change of the relaxation oscillator. The microcontroller  3  is able to sense this frequency change by continuously measuring the oscillation frequency and comparing it every time with a pre-determined threshold frequency. If the current frequency falls below this threshold frequency, the microcontroller  3  recognizes a human touch. To protect the sensitive input of the microcontroller  3  from extreme Electro-Static Discharge (ESD), an ESD suppression circuitry  8  is used. 
     Referring to  FIG. 2 , a bridge rectifier  9  rectifies the AC voltage input  1  and an electrolytic capacitor  10  smooths the DC rectified output. A resistor  11  and a Zener diode  31  are used to regulate the 5 Volts required for the circuit operation. A small ceramic capacitor  12  is placed close to the microcontroller&#39;s  3  power supply to filter out any higher frequency noise. 
     A typical single-transistor  13  constant current driver is used to supply the required current for the four LEDs  14 . Each LED has a balancing resistor  15  to balance the current through each of the four LED branches. The overall current through all four branches is set by the emitter resistor  16 . The device is set to allow approximately 50 mA of current through, enough to brightly illuminate the housing with the four LEDs, but not high enough to stress or actuate the solenoid of the chime bell. 
     A dual anti-serial MOSFETs  17  circuit performs the AC switch. The gates of the two MOSFETs are pulled low with a pull-down resistor  18 . A small ceramic capacitor  19  along with the collector resistor  20  generates a delay to avoid accidental triggers upon power up or after recovering from a power failure. A small resistor  21  protects the delay capacitor  19  from high discharge currents through the transistor  22 . 
     The gates of the two MOSFETs  17  are controlled by a transistor  22 . As long as the base of the transistor is pulled high with a pull-up resistor  23 , the transistor operates in the saturation area and the gates of the MOSFETs  17  are kept LOW keeping the MOSFET switch OPEN. The resistor  35  provides a base bias to the transistor  22 . One end of the resistor  35  is connected to the microcontroller  3 , such that the resistors  23  and  35  together provide a voltage divider for applying a selected voltage high or low voltage to the transistor  22  as determined by operation of the microcontroller  3 . 
     An active LOW at the gate of the transistor  22  from the microcontroller  3  puts the transistor into the cut-off area. The gates of the two MOSFETs  17  are then driven HIGH effectively CLOSING the AC switch allowing current to run through, actuating the chime solenoid. 
     The touch sensor is based on the Frequency Change method. The internal comparator module of the microcontroller  3  along with a resistor R  24  and a capacitor C  25  perform a relaxation oscillator. The capacitor C  25  is rapidly charged through a blocking diode  26  from the output of the microcontroller&#39;s comparator  27 . The non-reversing input of the microcontroller&#39;s comparator  28  tests the voltage of the capacitor  25 . When the capacitor  25  is fully charged, the output of the comparator  27  is driven LOW. The blocking diode  26  blocks current to flow from the capacitor  25  back to the output of the comparator  27 , therefore the capacitor  25  slowly discharges through the resistor  24 . When the capacitor  25  is discharged to about 0.6V, the output of the comparator  27  is turned HIGH again and the cycle repeats. The comparator is internally coupled with a timer module used by the microcontroller  3  to measure the oscillation frequency. 
     The metallic part of the housing performs the touch pad  32 . To protect the sensitive input of the microcontroller  3  from Electro-Static Discharge ESD, two clamping diodes  33  and a limiting resistor  29  are used. The resistor reduces the inrush current of the ESD and the two clamping diodes ensures that anything above or bellow the acceptable voltage levels will not go through the microcontroller  3 . 
     When the touch pad  32  is touched, the human body capacitance is effectively added in parallel to the capacitor C  25 , thus increasing its capacitance. This capacitance increment changes the oscillation frequency of the relaxation oscillator described before. More specifically, the frequency is decreased. The microcontroller  3  continuously checks the oscillation frequency and compares it with a pre-determined threshold value. If the oscillation frequency falls bellow this threshold value, the microcontroller recognizes a touch. 
     When a touch is recognized, the LED current driver  5  is turned off. Then the transistor base  22  of the MOSFET switch  4  is driven LOW for a period of time. The gates of the two MOSFETs  17  are driven high effectively CLOSING the AC switch to actuate the chime solenoid. 
     When the microcontroller  3  recognizes a touch, the MOSFET AC Switch  17  is NOT kept closed for as long as the touchpad  32  is touched. Instead, the MOSFET AC Switch  17  is closed only for a period of time of a few hundreds milliseconds sending only a pulse to actuate the chime solenoid. This way, a smaller electrolytic capacitor  10  can be selected, effectively reducing the overall cost and size of the device. 
     When the microcontroller  3  recognizes a touch, the MOSFET AC Switch  17  is CLOSED for a period of time thus allowing current to run through the MOSFETs  17 . But this means that there is no voltage across the PSU  2  for as long the MOSFETs  17  conduct current. To maintain power across the microcontroller  3 , there is a large electrolytic capacitor  10 . The capacitor  10  stores energy when the tough pad  32  is not touched. The capacitor  10  will store enough energy to provide power to the microcontroller  3  when the MOSFET AC Switch  17  is closed. This way the microcontroller  3  does not reset due to brown out or power failure. 
     When the microcontroller  3  recognizes a touch, it first turns completely off the LED Current Driver. No power is consumed for the Current Driver or the LEDs  14  for as long the MOSFET AC Switch  17  is closed. This way the electrolytic capacitor  10  is able to maintain sufficient power for the microcontroller  3  during this time, otherwise the LEDs  14  would quickly drain all the power from the capacitor  10  turning completely off the microcontroller  3 . 
     A delay circuit provided by an RC Network comprised of Resistors (R)  20 ,  21  and a capacitor (C)  19  keeps the MOSFET gates LOW for a short period of time when the device is powered ON or revives after a brown-out or power failure. This is done because the output of the microcontroller  3  cannot be controlled for a short period of time when the microcontroller  3  revives from a reset. It could accidentally close the MOSFET AC Switch  17  which will eventually actuate the chime solenoid. The delay RC network  19 ,  20 ,  21  ensures that the microcontroller  3  has enough time to initiate before the MOSFET gates can be driven HIGH. 
     A constant current driver  5  comprised of a single transistor  13  is used to control the LED current to the LEDs  14  instead of a simple limiting resistor. The first advantage of using the single current driver  5  is that the LEDs  14  can be indirectly controlled by the microcontroller  3  drawing only a few microamperes when the driver  13  is turned OFF, allowing thus a smaller capacitor  10  to be used. A second advantage is that the IDTPS can effectively control the maximum current that will flow through the chime installation regardless of the chime installation voltage, extending therefore the operating voltage range of the IDTPS. A third advantage of use of a the current driver  5  over a limiting resistor is that the brightness of the LEDs  14  is maintained the same regardless of the operating voltage. 
     The transistor  13  chosen for the LED driver  5  has a high power dissipation capacity (600 mW). With properly designed copper thermals on the PCB for a heat sink, the device is able to dissipate all the power needed when it is called to operate at higher voltage than 16 VAC. 
     Two clamping diodes  33  and one inrush limiting resistor  29  ensures that the device can stand the extreme ESD that will be experienced from human bodies wearing woolen clothes touching touch pad  32 . 
     The current configuration provides zero-force actuation for a chime bell touch button using capacitive touch technology to sense a touch. The device is sensitive enough to sense a touch through a glove or other clothing, from any part of the human body making it user friendly for handicap people. When a touch is sensed only one short pulse is generated to ring the chime bell, such that the chime bell circuit including the transformer and the chime bell are protected from overload as could happen from a jammed chime button. The device has a metallic housing, a metallic base and a printed circuit board (“PCB”). The metal housing provides the touch pad, and it has an electrically-insulating layer to protect the sensitive electronics from Electro-Static Discharge (“ESD”). The metal housing is preferably is fixed to the metallic base with one screw which is used to electrically connect the metallic housing with the metallic base. The is fixed on the metallic base with a plurality of screws which electrically connect the PCB touch terminals with the metallic base. Mounted to the PCB are a microcontroller, a large capacitor, a mosfet AC switch, a plurality of LEDs and a plurality of the other electronic parts described herein. A large capacitor is charged from the chime bell circuit. When the device is not touched, the microcontroller is powered from the chime bell circuit. When the device is touched, the microcontroller and the mosfet AC switch are powered from the large capacitor for the duration of the ring-pulse. When the device is not touched, the LEDs are bright to indicate the chime button. When the device is touched, the LEDs are automatically turned off to drop down the power consumption from the large capacitor. 
     Referring to  FIG. 3 , a more cost-effective MOSFET AC switch circuit is shown. The switch circuit can be implemented between the bridge rectifier  9  of the PSU  2  and the DC voltage outputs, using only one MOSFET  17  instead of the two anti-serial MOSFETs  17  shown in  FIG. 2 . An extra decoupling diode  30  is required to decouple the electrolytic capacitor  10  form the AC switch when the switch is CLOSED. A pull-down resistor  18  ensures that the gate of the MOSFET  17  is kept LOW during power up. A delay circuit composed by a small capacitor  19  and a resistor R  20  ensures the MOSFET  17  will not accidentally fire after power up, brown out or if the circuits recovers after a power down, until the microcontroller  3  is fully initialized. When the microcontroller  3  recognizes a touch, current runs through the bridge rectifier  9  and then through the MOSFET  17 , effectively actuating the chime solenoid. 
       FIGS. 4-10  are flowcharts showing a process for operating in the microprocessor  3  for controlling the system, storing settings in memory and operating the microprocessor  3  to continually calibrate a capacitance of a touch surface to discriminate a human touch from moisture, small animals and other type environmental contacts. Referring to  FIG. 4 , when powered up, the system Starts in step  40  and runs an Initialization routine  41  to set up the registers, RAM positions, inputs and outputs. The system will then load a predetermined set of parameters for the Touch Threshold and the Release Hysteresis in step  42 . Next the system will run the Calibration Routine in step  43  during which it will determine the current oscillation frequency and it will try to set the optimum oscillation frequency. When done the pointer jumps to the Sensing Loop in step  50 . 
     Referring to  FIG. 5 , the Sensing Loop in step  50  operates to loop continuously until a touch or release condition is detected. Immediately after entering the Sensing Loop in step  50  a specific short delay is executed in step  51 . Then in step  52  the system will acquire the current frequency count of the capacitance oscillator applied to the inputs  28  and  27  of the microprocessor  3 . This frequency depends on the resistor R  24  and the capacitor C  25  of the RC network, and the capacitance of the touch pad  32 . When the frequency is acquired, the system will Average this Frequency Count in step  89 . Then the process in step  53  will test the current frequency with the Touch Threshold and decide whether the sensor is touched in step  54 . If in step  54  a determination is made that the sensor is touched, the process will move to step  57  and will clear the Release Counter and then in step  58  will increase the Touch Counter  58 . Then the process moves to step  59  and determines whether the Touch Counter is greater than a specific threshold, if so, in the process moves to step  59   b  and considers the touch pad  32  as being touched and will jump to step  66  in  FIG. 7 . If in step  69  a determination is made that the touch pad  32  is not being touched, the process will return to the Loop Delay and repeat step  51 . If in step  54  a determination is made that the sensor  32  is not being touched, then the system proceed to step  55  and test the current frequency with the release hysteresis. If the system decides that the sensor  32  is not released, it will return to the Loop Delay of step  51 . If not, the system will proceed to step  60  and test the Touch Flag. If the Touch Flag is set, this means that the sensor is released after being touched and the system will proceed to step  62  and reset the microprocessor  3 . Otherwise the system will proceed to step  63  and will clear the Touch Counter and then in step  64  increase the Release Counter  64 . Then the system will proceed to step  65  to test the Release Counter. If in step  65  a determination is made that the release counter greater than a specific threshold the system considers that the sensor is not touched and will jump to step  45  in  FIG. 6 . Otherwise the system will proceed to the Loop Delay step  51 . 
     Referring to  FIG. 6 , from step  45  the process will first clear the Release Counter in step  46  and then will deactivate the Chime Driver in step  47  in case it was activated. The process will then turn ON the LED Driver in step  48  to ensure that thee LEDs  14  are lit. Then it will clear the Touch Flag in step  59  and in step  50  will return to the process of  FIG. 6 . 
     Referring to  FIG. 7 , when in step  59  of  FIG. 5  a determination is made that the sensor pad  32  is touched, the process will move to step  66  in  FIG. 7  and then in step  67  will clear the Touch Counter. It will then test the Touch Flag in step  68  by determining whether the Touch Flag is set. If the Touch Flag is set this means that the sensor  32  was already touched so the system will return to the Sensing Loop of step  50  in  FIG. 5 . If in step  68  a determination is made that the Touch Flag was not set, the process will proceed to step  69  and first turn OFF the LED Driver  69 . The process will then in step  70  remain idle for a short delay period of 30 mSec  70  and in step  71  will send a pulse to the chime solenoid by activating the mosfet switch  17  in step  71 . The process will then wait in step  72  for a duration of time and deactivate the mosfet switch in step  73 . The process will wait in step  74  for a short delay, then in step  75  will turn ON the LED Driver  5 , and then in step  76  will set the Touch Flag  78 . The processing will then return to the Sensing Loop step  50  of  FIG. 5 . 
     Referring to  FIG. 8 , the calibration step  43  of  FIG. 4  is depicted. In step  77  the Calibration routine is initiated. The Calibration routine will test different timer settings to decide what is the optimum setting for a specific touch pad  32 . In step  78  a 1 mSec delay  78  pause occurs for the program flow to allow the oscillator circuit  6  to settle. Then in step  79  a frequency count is acquired and then in step  80  the frequency counter is tested for an overflow. If in step  81  a determination is made that the frequency counter overflowed, the system will move to step  86  and decrease the timer setting. The system will then test the timer setting in step  87 . If the timer setting has reached a minimum setting then the system cannot calibrate the sensor and it will flash the LEDs to indicate the error in  88 , otherwise the system will return back to the 1 mSec delay of the calibration routine in step  78 . If in step  81  a determination is made that the frequency counter has not overflowed then the system will acquire once more the current frequency in step  82 . The process will then use the Sensitivity Value to get the Touch Threshold from the current frequency count in step  83  and it will use the Hysteresis Value to get the Release Hysteresis from the current frequency count in step  84 . The process will end in step  85  and return to the step  44  in  FIG. 4 , which then proceeds to the step  50  in  FIG. 5 . 
     Referring to  FIG. 9 , the Average Frequency Count routine of step  89  of  FIG. 5  is depicted. This routine averages 16 frequency counts. The result then is used to dynamically recalibrate the sensor. The routine starts by testing the Touch Flag to see if the sensor is touched step  90 . If the sensor is touched then the routine ends in step  91 , and returns to step  53  in  FIG. 5 . If the sensor is not touched then the Averaging Sampling Counter is increased by one in step  92 . If the Averaging Sampling Counter is not overflowed then the routine ends step  94  and returns to step  53  in  FIG. 5 . Otherwise the routine proceeds by re-initializing the Averaging Sampling Counter for the next calls in step  95 . Then the system sets a pointer to a specific RAM address and adds the Average Counter in step  96 . Then the process stores the current frequency count to this RAM address in step  97  and increases the Average Counter in step  98 . The process then tests the Average Counter in step  99  and if the Average Counter is less than 16 the routine ends in step  100  and returns to step  53  in  FIG. 5 . Otherwise this means that a total of 16 counts are stored into the RAM buffer. The system clears the Average Counter in step  101  to prepare the Average Counter for the next calls. Then the process averages all 16 RAM positions in step  102  by adding them all together to a 16-bit register and then divides this register by 16. Using this average the system extracts a new Sensitivity Value as a fraction of the Average Value in step  103 . Next the process extracts the new Sensitivity Hysteresis as a fraction of the Sensitivity Value previously noted in step  104 . Then the process uses these two new values to update the Touch Threshold using the Sensitivity Value in  105  and the Release Hysteresis using the Hysteresis Value in step  106 . At that point the Average Frequency Count routine ends  107 , and the process returns to step  53  in  FIG. 5 . 
     Calibration, Reset after Touch, Hysteresis and recalibration are preformed by averaging detected values. Touch sensors are sensitive by their nature. They operate by sensing the difference in capacitance on a sensor. The size, material and placement of the touchpad alters the quiescence capacitance radically. The calibration routine in step  43  during start-up rapidly tests several frequency divisions to discover which one brings the center frequency (in quiescence) in optimum count so that the sensitivity is kept to maximum. This way different touch pads  32  can be utilized just as effectively. Capacitance touch sensors are also very sensitive to water. Water droplets or frozen moisture alters the capacitance radically. During the normal operation, the system always measures and averages the quiescence frequency a number of times each minute. Whenever a new average frequency arises from this operation the system recalibrates itself to match this new frequency. Therefore, water droplets from rain or frozen moisture which slowly accumulate on the touch pad  32  are compensated and the sensor operates with the new conditions. 
     Whenever the sensor is touched, it may alter its quiescence frequency afterwords as a result of the physical contact. If for example frost or water has accumulate on the touch pad  32 , the operator may wash out this mass by touching the touch pad  32 . The averaging routine is not very effective in compensating such rapid changes. Therefore, whenever the sensor is touched and released the system resets itself in step  62 . This feature forces the system to rapidly recalibrate with the new conditions. The reset condition after a touch/release in step  62  can potentially bring the system in a low sensitivity operation in some cases. For example if the operator touches the touch-pad  32  but he then removes the finger very slowly, then a reset condition will rapidly calibrate the sensor at a very low sensitivity because it will try to compensate the finger of the operator which is still in the proximity of the sensor. To avoid this situation a hysteresis is introduced. The system recognizes thee conditions instead of two. The first is the touch condition, as a result of a rapid capacitance increment. The second state is the release condition as a result of a rapid capacitance decrement. The third state is the release hysteresis. This state occurs after a rapid capacitance decrement (release condition), but the amount of decrement is bellow the Release Hysteresis in step  55 . So, if the operator touches the sensor (Touch Condition) and then tries to confuse the system by retracting the finger very slowly, the system will take no further action until the measured capacitance is less than the capacitance after the touch condition minus the Release Hysteresis. 
     Referring to  FIG. 10 , a broad flowchart of the system&#39;s operation is depicted. The sysem starts at step  109 , and then initializes the microcontroller in step  110  for proper operation (modules, RAM, ports, interrupts, registers). Then the system runs the calibration routine in step  111  during which the system swiftly compensates the operating conditions so that it achieves maximum sensitivity. Immediately after the system jumps into the Sensing Loop in step  112  which loops indefinitely until a touch or release condition is detected. 
     The first step after beginning the Sensing Loop in step  112  is to acquire the current frequency in step  113  and then to average this frequency in step  114 . The averaging routine ins tep  114  compensates any environmental changes such as water droplets from rain or moisture or frost to maintain proper operation. Then the system tests the current frequency in step  115  to detect a touch. If the sensor is touched in step  116  it jumps into a filtering routine in step  123  to filter out false triggering. If a false triggering is detected the program goes back to the beginning of the sensing loop step  112 . If no false triggering, the system checks if it was already touched in step  124  and if it was touched the system goes back to the beginning of the sensing routine of step  112  without taking any further action. Otherwise the system turns off the LED driver in step  125  to preserve power and sends a pulse to the AC MOSFET switch in step  126  of predetermined duration to activate the chime solenoid. Then the turns ON the LED driver in step  127  and goes back to the beginning of the sensing loop in step  112   
     If during the testing of the frequency count in step  115  the system does not recognize a touch, it tests for a release condition in step  117 . If no release condition is detected in step, the program goes back to the beginning step  112  to again enter of the sensing. If a release condition is detected in step  117 , then the system checks whether this condition follows a touch condition in step  118  and if it does then it resets itself in step  120 . This reset forces the system to swiftly recalibrate to the new conditions. If the release condition does not follow a touch condition then the sytem jumps to a filtering routine in step  119  to filter out false release condition detections. If a false release condition is detected, the system goes back to the beginning of the sensing loop step  112 . Otherwise the system deactivates the chime driver (AC MOSFET Switch  17 ) in step  121 , turns ON the LED driver in step  122 , and then returns to the beginning sensing loop step  112 . 
     The following are materials used for particular reference numerals in a preferred embodiment:
           1 : Input terminals KEYSTONE 8191 SCREW_TERMINAL     3 : Microchip PIC12F615T-I/SN SOIC 8-Pin FLASH-Based CMOS Microcontrollers     9 : MB8S Bridge Rectifier SOIC-4     10 : 220 UuF 35V Electrolytic Capacitor     11 : 1 KOhm R1206     12 : 0.1 uF 16V 0603 MLCC Capacitor     13 : DNBT8105-7 SOT23-BEC-NPN Transistor     14 : ASMT-UWB1-NX3G2 WARM WHITE 3500K     15 : 1 KOhm R0805     16 : 100 Ohm R1206     17 : IRLML0060TRPBF N-Channel Power MOSFET     18 : 1 MOhm R0805     19 : 10 pF 50V 0805 MLCC Capacitor     20 : 12 KOhm R0805     21 : 20 Ohm R0805     22 : MMBT2222A SOT23 NPN Transistor     23 : 100 KOhm R0805     24 : 68 KOhm R0805     25 : 1 pF 16V 0603 MLCC Capacitor     26 : MBRA140TRPBF Schottky Diode 403D     29 : 220 Ohm R0805     31 : 5.1V 0.5 W Zener Diode MiniMELF     33 : LL4148 Small Signal Diode MiniMELF     34 : 1.5 KOhm R0805     35 : 2.2 KOhm R0805       

     The current configuration provides zero-force actuation for a chime bell touch button using capacitive touch technology to sense a touch. The device is sensitive enough to sense a touch through a glove or other clothing, from any part of the human body making it user friendly for handicap people. When a touch is sensed only one short pulse is generated to ring the chime bell, such that the chime bell circuit including the transformer and the chime bell are protected from overload as could happen from a jammed chime button. The device has a metallic housing, a metallic base and a printed circuit board (“PCB”). The metal housing provides the touch pad, and it has an electrically-insulating layer to protect the sensitive electronics from Electro-Static Discharge (“ESD”). The metal housing is preferably is fixed to the metallic base with one screw which is used to electrically connect the metallic housing with the metallic base. The is fixed on the metallic base with a plurality of screws which electrically connect the PCB touch terminals with the metallic base. Mounted to the PCB are a microcontroller, a large capacitor, a mosfet AC switch, a plurality of LEDs and a plurality of the other electronic parts described herein. A large capacitor is charged from the chime bell circuit. When the device is not touched, the microcontroller is powered from the chime bell circuit. When the device is touched, the microcontroller and the mosfet AC switch are powered from the large capacitor for the duration of the ring-pulse. When the device is not touched, the LEDs are bright to indicate the chime button. When the device is touched, the LEDs are automatically turned off to drop down the power consumption from the large capacitor. 
     Although the preferred embodiment has been described in detail, it should be understood that various changes, substitutions and alterations can be made therein without departing from the spirit and scope of the invention as defined by the appended claims.