Abstract:
A system for controlling a relay to reduce acoustic noise of connections and disconnections being made within the relay. An impact of closing and opening contacts in a relay may cause the acoustic noise. For instance, when a relay coil causes the contacts to come together for a connection, an acoustic noise may occur. When the relay coil causes the contacts to separate for breaking a connection, another acoustic noise may occur. Reduction of acoustic noise may be realized by controlling movement of the contacts. The present system may control current to the relay coil to slow the movement of contacts while closing and opening to reduce the acoustic noise.

Description:
BACKGROUND 
       [0001]    The present disclosure pertains to relays and particularly to control of relays. 
       SUMMARY 
       [0002]    The disclosure reveals a system for controlling a relay to reduce acoustic noise of connections and disconnections being made within the relay. An impact of closing and opening contacts in a relay may cause the acoustic noise. For instance, when a relay coil causes the contacts to come together for a connection, an acoustic noise may occur. When the relay coil causes the contacts to separate for breaking a connection, another acoustic noise may occur. Reduction of acoustic noise may be realized by controlling movement of the contacts. The present system may control current to the relay coil to slow the movement of contacts while closing and opening to reduce the acoustic noise. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0003]      FIG. 1  is a block diagram of an example system for controlling a relay; 
           [0004]      FIG. 2  is a diagram outlining the major components of the system; 
           [0005]      FIG. 3  is a diagram of the system showing some details of the major components; and 
           [0006]      FIG. 4  is a diagram of a schematic of an example circuit for the system. 
       
    
    
     DESCRIPTION 
       [0007]    The present system and approach, as described herein and/or shown in the Figures, may incorporate one or more processors, computers, controllers, user interfaces, wireless and/or wire connections, and/or the like, wherever desired. 
         [0008]    The acoustical noise generated by the relay of a thermostat or another device may annoy users. Requests to manufacturers to create low noise relays having low noise at reasonable costs are not necessarily accepted. For example, one relay having low noise that may be available which is good for limited amperage and sold by allocation. Further, such relay may be a disadvantageous single sourced component. 
         [0009]    The present circuit may circumvent various noted issues. The circuit may be used with virtually any regular conventional relay and reduce the acoustical noise of the relay during operation to an acceptable level. 
         [0010]    The circuit may control the current that is delivered to the relay by limiting and diverting it. The limiting and diverting current may delay the closing and opening action of the relay and thus reduce the sound emitted by an impact of the contacts with each other or breaking of the contacts. During a breaking of the contacts, at least one contact may spring back to a stop thus making a noise. 
         [0011]    With the present circuit in a closing of the relay, a current control circuit may limit the current provided to the coil of the relay for a gradual closing of the contacts. The current control circuit may in effect be used to divert part of the current. As a result, the speed and the impact of the contacts may be reduced and thus reduce or minimize an acoustic noise of the closing contacts. 
         [0012]    For opening the relay, a current control circuit may be utilized to keep the current flowing through the coil to the relay, in which the current may be slowly reduced in magnitude for a gradual opening of the contacts. The gradual opening of the contacts may reduce or minimize an acoustic noise of the opening contacts. 
         [0013]    Relay contacts may be opened or closed with an application of current to a relay coil affecting the contacts. Likewise, relay contacts may be opened or closed with a removal of current from the relay coil affecting the contacts. An illustrative example described herein may have relay contacts that close upon an application of current to the relay coil and have relay contacts that open upon removal of current from the relay coil. 
         [0014]      FIG. 1  is a block diagram  11  of the present circuit. A drive signal may be provided on a line  12  to a current switch  13 . Current switch  13  may be connected to a relay coil  15  via a line  14 . A capacitor based current control circuit  18  may be connected to line  14 . A capacitor based current control circuit  16  may be connected to lines  14  and  17 . 
         [0015]      FIG. 2  is a diagram outlining the major components of an example of a present circuit  21 . A switch  61  may have an input for a drive signal. Switch  61  may have a line  34  that is connected to one end of a coil  25  of relay  22 . Coil  25  may have another end connected to a polarity of voltage source via line  37 . Switch  61  may connect line  34  to another polarity, ground or reference terminal  30  (ground) of the voltage source to result in a current flow through coil  25  so as to close or bring contacts  23  and  24  in connection with each other. Switch  61  may also disconnect line  34  from ground  30  to result in a ceasing of current flow through coil  25  so as for contacts  23  and  24  to break away and disconnect from each other. In relay  22 , contact  23  may be drawn into connection with contact  24  with a magnetic force of coil  25  caused by current flow through the coil, Contact  24  may be stationary relative to coil  25  and a structure of relay  22 . Contact  23  may have spring-like tension which causes contact  23  to be apart from contact  24  when not subject to a magnetic force of coil  25 . When contact  23  breaks away form contact  24 , contact  23  may move back to a stop  20 . When contact  23  impacts stop  20 , there may be an acoustic noise from the impact. Similarly, when contact  23  is drawn to an impact with contact  24  by a magnetic force from coil  25 , there may be an acoustic noise from the impact. A configuration of relay  22  shown in the Figures of the present description is merely an illustrative example. Relay  22  may have various configurations with many kinds of assortments of contacts and arrangements of a relay coil or coils, or other magnetic force producing mechanisms. An example relay  22  may be a PCFN-112D2M. This relay may be available at vendors of electronic parts. 
         [0016]      FIG. 2  shows a sustainer  63 , connected between line  34  and ground  30 , which may sustain the current through coil  25  when switch  61  disconnects coil  25  from electrical power. With current to coil  25  being sustained for a period of time, though at a magnitude decreasing from an original magnitude provided by switch  61  to coil  25 , contacts  23  and  24  may open with smaller impact and less acoustic noise than the impact and noise if the current were not sustained. A suppressor  62 , connected between line  34  and line  37 , may hinder a full magnitude of current being provided to coil  25  by switch  61  when connecting coil  25  to the electrical power. Suppressor  62  may shunt or bypass some of the current when initially provided to coil  25  by switch  61 . With current to coil  25  being suppressed for a period of time, though resulting in an increasing magnitude to coil  25 , contacts  23  and  24  may close with a smaller impact and less acoustic noise than the impact and noise if the current were not suppressed. 
         [0017]      FIG. 3  is a diagram of circuit  21  showing more detail relative to the diagram of  FIG. 2 . Switch  61  may have a current switch  71 . Sustainer  63  may have a variable current control circuit  73  connected to a circuit having a capacitor  36  and a resistor  55 . Suppressor  62  may have a variable current control circuit  72  connected to a circuit having a capacitor  26  and a resistor  51 . 
         [0018]      FIG. 4  is a diagram of a schematic of circuit  21 . The schematic is an illustrative example of circuit  21 . Circuit  21  may be implemented with other layouts of various components. Transistors in the circuit may be 2N3904 transistors. The diodes may be 1N4148 diodes. These components may be available at vendors of electronic parts. Other kinds of transistors, diodes or components may be used. The values of the capacitors and resistors may be other than those as indicated in the schematic. 
         [0019]    To begin, groupings of the components in the schematic may be noted according to the diagram of  FIG. 3 . Current switch  71  of switch  61  may have transistors  43  and  44  and resistors  52 - 54 . Variable current control circuit  73  of sustainer  63  may have transistors  45  and  46 . Variable current control circuit  72  of suppressor  62  may have transistors  41  and  42 . Additional connections and description of components may be provided herein. 
         [0020]    Line  37  may be connected to a voltage and to a positive terminal of relay coil  25 . A negative terminal of relay coil  25  may be connected to a line  34 . An NPN transistor  41  may have a collector connected to line  37  and an emitter connected to line  34 . An NPN transistor  42  may have a collector connected to line  37  and an emitter connected to a base of transistor  41 . A capacitor  26  may have a first terminal connected to line  37  and a second terminal connected to a base of transistor  42  via a diode  58  having an anode connected to the second terminal of capacitor  26  and a cathode connected to the base of transistor  42 . Diode  58  may be for a protection purpose. Capacitor  26  may have a value of about 0.47 microfarads. A 51K ohm resistor  51  may have first end connected to the anode of diode  58 , and a second end connected to line  34 . A voltage or signal on the base of transistor  42  may control a closing of relay contacts  23  and  24 . 
         [0021]    An NPN transistor  43  may have a collector connected to line  34  and an emitter connected via a 2.2 ohm resistor  52  to a ground or zero voltage reference line  30 . A drive signal line  32  may be connected to a first end of a 1K ohm resistor  53 . A second end of resistor  53  may be connected to a base of transistor  43 . A collector of an NPN transistor  44  may be connected to the base of transistor  43 . An emitter of transistor  44  may be connected to line  30 . A base of transistor  44  may be connected to the emitter of transistor  43 . Line  32  may also be connected to a first end of a 51K ohm resistor  54 . A second end of resistor  54  may be connected to line  30 . 
         [0022]    An NPN transistor  45  may have a collector connected to line  34  and an emitter connected to line  30 . An NPN transistor  46  may have a collector connected to line  34  and an emitter connected to a base of transistor  45 . A 2.2 microfarad capacitor  36  may have a first terminal connected to line  34  and a second terminal connected to an anode of diode  57 . A cathode of diode  57  may be connected to the base of transistor  46 . Diode  57  is for a protection purpose. A 51K ohm resistor  55  may have a first end connected to the base of transistor  46  and a second end connected to line  30 . A voltage or signal on the base of transistor  46  may control an opening of relay contacts  23  and  24 . 
         [0023]    At a steady state where the voltage of a drive signal at line  32  is low, transistors  43  and  44  may be off. The voltage on line  34  may be somewhat higher than ground  30 . Transistors  45  and  46  may be off since capacitor  36  would be charged and the base to transistor  46  would be pulled down by resistor  55 . So line  34  may float up towards the voltage level on line  37 . Transistors  41  and  42  would be off in this steady state since capacitor  26  would be discharged through resistor  51  and the base of transistor  42  would be close to the voltage of the emitter of transistor  41 . 
         [0024]    As the drive signal at line  32  goes up, transistors  43  and  44  go on pulling the voltage down and line  34  as current flows from line  34  to line  30 . This should pull current through the relay; however, as the emitter voltage of transistor  41  is pulled down, transistors  42  and  41  will tend to turn on since the base voltage will be held higher from the emitter voltage until capacitor  26  charges current through resistor  51  and the base of transistor  42 . While transistor  41  is on, current may be shunted or bypassed from coil  25  causing contacts  24  and  25  to be slowed down in closing thereby reducing acoustic noise of the contacts closing. As capacitor  26  is completely charged, transistor  41  will be off and current flow through coil  25  will be sufficient for contacts  23  and  24  to be closed when a steady state of the circuit  21  is reached. 
         [0025]    At the steady state where the voltage of a drive signal on line  32  is high, transistors  43  and  44  may remain turned on and the voltage on line  34  may be close to voltage  30  except for a small voltage drop through resistor  52 . With a low voltage across transistors  45  and  46 , and resistor  55  discharging capacitor  36  having pulled the base of transistor  46  down to a voltage level of line  30 , transistors  45  and  46  may be regarded as being turned off. Also, as noted above, transistors  41  and  42  may be regarded as being turned off since the base of transistor  42  is pulled down by resistor  51 , having charged capacitor  26 , to a voltage level between line  37  and base of transistor  42 . 
         [0026]    When drive signal on line  32  goes down, transistors  43  and  44  may turn off and stop conducting current from coil  25 . The voltage on line  34  will tend to go up which may result in transistor  45  and  46  to be turned on since the voltage on the terminal of capacitor  36  is connected to line  34 , and the other terminal of capacitor  36  is connected to the base of transistor  46 . Line  34  is raised in voltage sufficient to keep transistors  46  and  45  on thereby resulting in a continued flow of current through coil  25  and preventing a sudden opening of contacts  23  and  24 . However, as resistor  55  and transistor  46  and  45  charges capacitor  36 , the voltage of line  34  goes up reducing the voltage across coil  25  thereby reducing the current flowing through coil  25  and resulting in a gradual opening of contacts  23  and  24  and a reduction of acoustic noise of the contacts. The voltage level on line  34  may reach the level on line  37  as circuit  21  approaches a steady state with the drive signal on line  32  at a low level. 
         [0027]    To recap, an approach, for reducing contact noise in a relay, may incorporate restraining movement of one or more contacts relative to another one or more contacts of a relay upon a connection or disconnection of a source of current to a coil of the relay to reduce contact noise. Restraining movement of the one or more contacts relative to the other one or more other contacts upon the connection of the source of current may incorporate diverting a portion of an initial current destined for the coil for a first period of time. Restraining movement of the one or more contacts relative to the other one or more other contacts upon the disconnection of the source of current may incorporate continuing a portion of a final current to the coil for a second period of time. 
         [0028]    The connection or disconnection of the source to the coil may be provided by a switch connected to the source of current and to the coil. 
         [0029]    The first period of time may be provided by a time constant of a first resistive capacitive circuit. The second period of time may be provided by a time constant of a second resistive capacitive circuit. 
         [0030]    Diverting a portion of the initial current destined for the coil may be accomplished by a circuit connected in parallel with the coil that begins with a conductance sufficient to conduct some of the current that would otherwise be conducted by the coil upon the connection of the source of current to the coil. Continuing a portion of the final current to the coil may be accomplished by a circuit connected in parallel with the switch that begins with a conductance sufficient to conduct some of the current that was otherwise conducted by the switch before the disconnection of the source of current. 
         [0031]    A magnitude of a diverted portion of the initial current destined for the coil may varies from a first value to a second value during the first period of time. A magnitude of a continued portion of the final current to the coil may vary from a third value to a fourth value. The first value may be equal to or greater than the second value. The third value may be equal to or greater than the fourth value. 
         [0032]    A relay contact noise reduction system may incorporate a switch connected to a relay, a suppressor connected to the relay, and a sustainer connected to the relay. The suppressor may hinder current flow to the relay upon a connection of current from the switch to the relay for a first predetermined period of time. The sustainer may maintain a current flow to the relay upon disconnection of current from the switch to the relay for a second predetermined amount of time. 
         [0033]    Hindering current flow in the relay upon connection of current from the switch to the relay may reduce noise caused by relay contacts coming in contact with each other. Maintaining current flow in the relay upon disconnection of current from the switch to the relay may reduce noise caused by relay contacts breaking contact from each other. 
         [0034]    The first predetermined amount of time may be based on a time constant of a resistor and capacitor circuit. The second predetermined amount of time may be based on a time constant of a resistor and capacitor circuit. 
         [0035]    The suppressor may hinder the current flow but with an increasing magnitude of the current during the first determined amount of time. The sustainer may maintain the current flow but with a decreasing magnitude of the current during the second determined amount of time. 
         [0036]    The suppressor may incorporate a first variable current control circuit, and a first resistor capacitor circuit connected to an input of the first variable current control circuit. The sustainer may incorporate a second variable current control circuit, and a second resistor capacitor circuit connected to an input of the second variable current control circuit. 
         [0037]    The current switch may connect and disconnect a voltage supply to the relay. The suppressor may divert current from the relay during an initial connection of the voltage supply to the relay. The sustainer may provide current to the relay during an initial disconnection of the voltage supply from the relay. 
         [0038]    Hindering current flow in the relay upon connection may reduce a speed of the relay contacts coming into connection with each other. Maintaining current flow in the relay upon disconnection of current from the switch to the relay may reduce a speed of relay contacts breaking from each other. 
         [0039]    A relay acoustical noise reduction circuit may incorporate a current switch having a connection for a drive signal and a connection to a coil of a relay having at least one pair of contacts, and a first capacitor based current control circuit having a connection to the coil of the relay. The first capacitor based current control circuit may minimize acoustic noise of a pair of contacts by controlling current to the coil of the relay. 
         [0040]    The drive signal may be a voltage that has a first magnitude to close the relay and a second magnitude to open the relay. To close the relay may be to bring a pair of contacts in contact with each other. To open the relay may be to separate a pair of contacts from contact with each other. 
         [0041]    The relay acoustical noise reduction circuit may further incorporate a second capacitor based current control circuit having a connection to the coil of the relay. The first capacitor based current control circuit may sustain a current flow through the coil for a first period of time after the current switch receives the voltage having the second magnitude to open the relay. The second capacitor based current control circuit may suppress a current flow through the coil for a second period of time after the current switch receives the voltage having the first magnitude to close the relay. 
         [0042]    The first period of time may be determined by a time constant of a first capacitance and a first resistance. The second period of time may be determined by a time constant of a second capacitance and a second resistance. 
         [0043]    When the current switch discontinues a flow of current in the coil, the first capacitor based current control circuit may sustain a flow of current at a first magnitude that decreases during the first period of time to a second magnitude. 
         [0044]    When the current switch begins a flow of current in the coil, the second capacitor based current control circuit may suppress the flow of current at a first magnitude that increases during the second period of time to a second magnitude. 
         [0045]    The first capacitor based current control circuit may sustain the current flow through the coil for the first period of time after the current switch receives the voltage having the second magnitude to open the relay, to permit contacts of the relay to break away from each other slowly to minimize acoustic noise of the contacts. 
         [0046]    The second capacitor based current control circuit may suppress a current flow through the coil for the second period of time after the current switch receives the voltage having the first magnitude to close the relay, to permit contacts of the relay to come together slowly to minimize acoustic noise of the contacts. 
         [0047]    In the present specification, some of the matter may be of a hypothetical or prophetic nature although stated in another manner or tense. 
         [0048]    Although the present system and/or approach has been described with respect to at least one illustrative example, many variations and modifications will become apparent to those skilled in the art upon reading the specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the related art to include all such variations and modifications.