Patent Publication Number: US-7715168-B2

Title: Controlled solenoid drive circuit

Description:
BACKGROUND 
   1. Field of the Invention 
   The present invention is generally directed to remote control switches. More particularly, the present invention is directed to remote control switches, such as lighting contactors that are electromagnetically-operated, mechanically held switch. One such remote control switch is disclosed in U.S. Pat. No. 4,430,579 which is herein entirely incorporated by reference and to which the reader is directed for further information. Such switches may be utilized in a wide range of different applications and are typically used for controlling lighting, heating and other like or similar type loads. A conventional remote control switch comprises essentially a circuit disconnect device that may be operated from one and/or a plurality of separate or interrelated control stations. Such control stations may be spread out over an area such as locally dispersed within a room, across a building, or some other remotely located area. However, aspects of the invention may be equally applicable in other scenarios as well. 
   2. Description of Related Art 
   A general diagram of a conventional remote control electromechanical switch circuit  10  is illustrated in  FIG. 1 . As can be seen from  FIG. 1 , remote control electromechanical switch circuit  10  comprises a primary switch  12  coupled to a remote control switch  14 . Primary switch  12  comprises mechanical contacts  40 . Primary switch  12  is coupled to AC line  28  and to an input of remote control switch  14 . Mechanical contacts  40  of primary switch  12  may be switched or positioned in either an up position  30  or a down position  32 .  FIG. 1  illustrates the mechanical contacts  40  of switch  12  in an up position  30 . Primary switch  12  is utilized to provide AC power from AC line  28  to remote control switch  14 . AC line  28  may comprise a conventional industrial AC line having 115/220 VAC, 50/60 Hz, however, the primary switch  12  may be utilized with other power grids as well. 
   Remote control switch  14  comprises a first set of contacts  16 , a diode  20 , a solenoid  24 , and a second set of contacts  26 . The first set of contacts  16  is coupled to an output of primary switch  12  whereas the second set of contacts  26  powers a load  27 . 
   Both solenoid control switch  36  and power load switch  38  are physically linked to solenoid  24 . Solenoid control switch  36  and a power load switch  38  have certain stable, mechanically locked positions and certain of these positions are illustrated in  FIG. 1 . For example, solenoid control switch  36  is illustrated in a down stable position  34  while power load switch  38  is illustrated in an up or open stable position  26   a . In this up or open position  26   a , load  27  remains unconnected 
   AC line is continuously coupled to the primary switch  12 . When primary switch contact  40  moves from the up position  30  to the down position  32 , the solenoid  24  energizes and thereby moves both of the physically linked contacts  16  and contacts  26  until a closed solenoid position  26   b  is reached. In this closed solenoid position  26   b , the solenoid  24  is disconnected from the line  28  via open contacts  16  in position  36 . Operation and control of remote control switch  14  may be explained in detail with reference to the various timing diagrams illustrated in  FIGS. 2(   a - e ). 
   For example,  FIG. 2   a  illustrates an exemplary AC line voltage  28  that may be applied to primary switch  12  and that is eventually applied at node  18  of mechanical remote control circuit  10 . Node  18  resides after contact  16  but before diode  20  in  FIG. 1 . Once AC line voltage  28  appears at diode  20  (such as at point  28   a  in  FIG. 2   c  diode  20  conducts only a positive half wave of the applied AC power to solenoid  24 . Consequently, this half wave voltage of AC voltage  28  will be applied to solenoid control switch  36  and is input to diode  20 . In one arrangement of such a remote control switch  14 , a one complete half wave of incoming AC voltage  28  ( FIG. 2   a ) is sufficient to complete a switch transition. Such a switch transition may typically occur on the order of approximately from about 5-7 milliseconds to about 10 milliseconds. A customer load  27  will be connected via power load switch  38  once the second set of contacts  26  of remote control switch  14  are completed or made. 
   In a first stable position, the contacts  40  of primary switch  12  reside in the upper position  30  and the contacts  26  of the solenoid control switch  38  also resides in the upper position  26   a  as illustrated in  FIG. 1 . When primary switch  12  is first activated (i.e., when the contacts  40  of switch  12  are switched from the upper position  30  to lower position  32 ), a first positive half wave of AC input voltage  28  (such as at point  28   a  in  FIG. 2   a ) passes diode  20  and energizes the solenoid  24 . The energized solenoid  24  pulls in both sets of mechanical contacts  26  and  16 , contacts  26  then move to a second stable position  26   b  and thereby provides power to the coupled load  27 . 
   The first positive half wave at point  28   c  of AC power  28  ( FIG. 2   a ) toggles both groups of contacts (i.e., solenoid control switch  16 , optional auxiliary contacts (not shown) and power load switch  26 ). When solenoid control switch  16  is first toggled, solenoid  24  is mechanically disconnected from AC input voltage  28 . Remote control switch  14  has now moved into its second stable position  26   b  and remains in this second stable position  26   b  until primary switch  12  is again actuated. 
   There are certain concerns that may arise with conventional mechanical switching circuits, such as the conventional circuit  10  illustrated in  FIG. 1 . For example, one concern relates to certain mechanical contact bounce, or contact “chattering” that may occur with the contacts  40  of primary switch  12 . For example, because moving contacts  40  of primary switch  12  has a certain mass associated with its structure as well as a certain spring rate with low damping, contacts  40  tend to bounce as they make and break a completed circuit. That is, when these normally open pair of contacts  40  are closed, these contacts  40  often tend to initially come together (“make”) and then tend to bounce/chatter off one another several times (“break”) before the contacts finally come to rest or remain in a desired (i.e., closed) stable position. Such contact bounce may result in unwanted contact arcing and this may unduly limit the operational lifetime of the contacts of primary switch. For example, certain consequences of this making and breaking of the primary switch contacts  40  may be illustrated in the timing diagram in  FIGS. 2   b - 2   e , and importantly the timing diagram  50  illustrated in  FIG. 2   b.    
   As shown in timing diagram  50  illustrated in  FIG. 2   b , when the contacts  40  of the primary switch  12  are in the first up position  30  and then when the contacts  40  are switched to closed or down position  32 , contacts  40  of primary switch  12  have a tendency to remain in an un-stable position, somewhere between the contact open position  30  and the contact closed position  32 . The contacts will eventually, however, reside in the down position  32  but only after a certain period of time t 1    44 . Depending on certain aspects of switch construction, mechanics, and design, such mechanical contact bounce can last up to approximately 15 milliseconds to 20 milliseconds. That is, as illustrated in  FIGS. 2   b  and  2   c , contact bounce T cb    43  may last from t 0    42  to t 1    44 . For further information on such mechanical bounce and its related issues, the reader is directed to http://www.elexp.com/t_bounc.htm which is herein entirely incorporated by reference and to which the reader is directed for further information. 
   Such contact bounce is normally undesired. For example, such contact bouncing often tends to interrupt current flow, as such current flow is eventually applied to energize a solenoid of a remote control switch, such as solenoid  24  illustrated in  FIG. 1 . For example, a timing diagram  56  of such a potentially problematic current flow is illustrated in  FIG. 2   c .  FIG. 2   c  illustrates a timing diagram  56  that represents the current available at node  18  directly before diode  20  as contacts  40  go through a bouncing state, transitioning between the up position  30  and the closed positions  32  illustrated in  FIG. 2   b . As can be seen from timing diagram  56 , contact bounce results in intermittent power or intermittent energy  52  during the one period from t 0    42  to t 1    44 . The intermittent power or energy  52  is available at diode  20  and before solenoid  24 . Contact bounce/chatter can adversely affect current flow and can also cause undesired contact arcing. 
   Consequently, as the timing diagram  58  of  FIG. 2   d  illustrates, there is limited or insufficient energy  60  available at node  18  for solenoid  24  to make a complete mechanical transition from its initially open stable state  26   a  to a desired closed stable state  26   b . Sufficient energy  62  to make such a transition will be available only once the electrical bounce or chatter of contacts  40  of switch  12  has subsided.  FIG. 2   d  illustrates a timing diagram of the varying energy that will be present after the diode  20  at node  22  but before solenoid  24 . Therefore, as illustrated in  FIGS. 2   d - e , prior to time t 2    70 , there is insufficient energy to complete a mechanical transition of second set of contacts  26 . As illustrated in  FIG. 2   e , during contact bounce as illustrated in  FIGS. 2   b  and  2   c , there is incomplete mechanical transition  66  that occurs during switch bounce illustrated in  FIG. 2   b . It is only after a certain period of time that takes into account contact bounce that there is a sufficient amount of energy available so that a complete mechanical transition  68  can occur. Consequently, the control of remote control switch  14  illustrated in  FIG. 1  tends to be inconsistent. This is true in part since the primary switch  12  may be switched at any time during the line voltage  28 . For example, under certain ordinary operating conditions, the remote switch completes its transition within a half of period of the line voltage such as within about 8.33 ms for 60 Hz AC line voltage and about 10 ms for 50 Hz AC line voltage. 
   Therefore, when a duration of contact bounce or chatter is critical to a switch transition time, remote control switch  14  will not have enough stored energy to make a reliable transition between an initial open state and a desired closed state. Therefore, as contacts  40  are loaded, contacts  40  will have a tendency to experience electrical chatter. This chatter may occur because solenoid  24  is not able to solidly transition from its open state to a closed state during this switch transition time. 
   One technique that has been utilized in an attempt to reduce or eliminate such mechanical contract bounce is to provide a circuit that introduces a solid state switch between the primary switch  12  and the remote control switch  14 . For example,  FIG. 3  illustrates such a solid state based solenoid control circuit  13 . 
   However, even such typical electronic solid state switch designs present certain operating and control limitations. For example, a solid state switch  48  coupled between a mechanical primary switch  12  and remote control switch  14  eliminates contact bouncing. However, one such concern with such an electronic solid state switch construction relates to what occurs if AC power is applied after solenoid  24 . That is, if AC power is applied to solenoid  24  after the beginning of a positive half wave of input AC voltage. As with the use of an electromechanical primary switch  12 , there may be insufficient energy to complete a switch transition. This concern regarding insufficient switch transition energy and the resulting synchronization issues with utilizing a solid state based switch raised by these concerns may be generally illustrated in the various timing diagrams presented as  FIGS. 4(   a - e ). 
   Returning to  FIG. 3 ,  FIG. 3  illustrates a solid state switch  48  coupled to a primary switch  12  and remote control switch  14 . Such a solid state switch  48  may comprise different solid state semiconductors such as triacs, MOSFETs, IGBTs, SCRs, as well as other like solid state components. In this exemplary arrangement, solid state switch  48  comprises a first triac  46  and a second triac  54  however other alternative arrangement may also be utilized. Also in this exemplary arrangement, a mechanical primary switch  12  (with potential contact bounce limitations) is utilized for solenoid control. In an up position  30  of a primary switch  12 , the first triac  46  will be in an ON state while the second triac  54  will be in an OFF state.  FIGS. 4(   a - e ) illustrate various timing diagrams for the solid state based switch circuit  13 . For example,  FIG. 4   a  illustrates a timing diagram of the AC line voltage  28  and  FIG. 4   b  illustrates a timing diagram  80 .  FIG. 4   c  illustrates a timing diagram  88  that represents a voltage available at node  18  directly before diode  20  as solid state switch  48  transitions from an OFF state to an ON state. Transitioning between the OFF state and the ON state illustrated in  FIG. 4   b . As can be seen from the timing diagram  88  in  FIG. 4   c , even for the solenoid control circuit  13  utilizing a solid state switch  48 , depending on where during the AC line cycle  28  that the solid state switch  48  transitions between its ON and OFF state (and where the primary switch  12  transitions between its up and down position (as shown in this example, transition occurs at point  28   d  in  FIG. 4   a ), there may still be insufficient or intermittent power or energy  102  available at diode  20 . Therefore, there will be insufficient energy to drive solenoid  24 . Consequently, as the timing diagram  104  of  FIG. 4   d  illustrates, even when utilizing a solid state switch  48 , there will often be insufficient energy available at node  18  for solenoid  24  to make a complete mechanical transition  111  from its closed state to the desired open state. Sufficient energy to make such a complete mechanical transition will be available only once the electrical bounce or chatter of contacts  40  of switch  12  has subsided.  FIG. 4   d  provides a timing diagram illustrating the varying amount of energy that will be present after the diode  20  at node  22  but before solenoid  24 . 
   Therefore as can be illustrated in the various timing diagrams illustrated in  FIGS. 4   d - e , prior to time t 1    71 , there is insufficient energy  102  to complete a mechanical transition of second set of contacts  26 . As can be seen from  FIG. 4   e , it is only after time t 1    71  that a complete mechanical transition  111  can occur. Consequently, as with the mechanical control switch illustrated in  FIG. 1 , control of the remote control switch  14  illustrated in  FIG. 3  even utilizing solid state switch  48  will tend to be inconsistent. 
   There is, therefore, a general need for a solenoid control circuit that provides for a controlled solenoid circuit that can consistently provide a sufficient amount of energy for contact closure. Also, there is a general need for a controlled solenoid circuit that reduces or even eliminates contact bounce or chatter. There is also, therefore, a general need for a control circuit that reduces certain undesired contact heating, contact arcing, and/or contact wear that can oftentimes occur during unwanted contact bounce. 
   SUMMARY 
   According to an exemplary embodiment, a solenoid drive circuit is provided. The circuit comprises a solenoid drive circuit input coupled to a primary switch. The primary switch comprises a first set of contacts residing in a first stable position. A remote control switch is coupled to an output of the primary switch and the remote control switch comprises a solenoid drive circuit having a predetermined delay. The predetermined delay energizes a solenoid after the primary switch contact transitions from a first stable position to a second stable position. 
   In an alternative arrangement, a controlled solenoid drive circuit comprises a primary switch, the primary switch is coupled to a line voltage and comprises a first set of contacts. A solenoid control switch is coupled to the first set of contacts, the solenoid control switch comprising a second set of contacts. A solenoid drive circuit has a time delay. The solenoid drive circuit is coupled between an output of the second set of contacts and a solenoid. After activating the primary switch, the solenoid drive circuit activates the solenoid after an expiration of the time delay. 
   In yet another alternative arrangement, a method of providing a controlled amount of power to a solenoid is provided. The method comprises the step of providing a primary switch, the primary switch comprises a set of mechanical contacts that transition between a first position and a second position and the step of receiving an input voltage at an input of the primary switch. A secondary switch is provided to an output of the primary switch, the secondary switch comprising a solenoid drive circuit. A switch transition is achieved from a first position to the second position during a single positive half wave of the input voltage. 
   These as well as other advantages of various aspects of the present invention will become apparent to those of ordinary skill in the art by reading the following detailed description, with appropriate reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments are described herein with reference to the drawings, in which: 
       FIG. 1  illustrates a typical schematic for a primary switch and a remote control electromechanical switch; 
       FIG. 2   a  is a line voltage of the AC line for the schematic illustrated in  FIG. 1 ; 
       FIG. 2   b  illustrates a timing diagram of the primary switch illustrated in  FIG. 1 ; 
       FIG. 2   c  illustrates a timing diagram of the diode illustrated in the remote control switch of  FIG. 1 ; 
       FIG. 2   d  illustrates a timing diagram of voltage before the solenoid illustrated in the remote control switch  FIG. 1 ; 
       FIG. 2   e  illustrates a timing diagram of the mechanical transition of switches  16 ,  26 , and  40  illustrated in the remote control switch of  FIG. 1 ; 
       FIG. 3  illustrates a typical schematic for a primary switch and a remote control electromechanical switch utilizing a solid state switch; 
       FIG. 4   a  is a line voltage of the AC line for the schematic illustrated in  FIG. 3 ; 
       FIG. 4   b  illustrates a timing diagram of the primary switch that may be utilized with a solid state remote control switch illustrated in  FIG. 3 ; 
       FIG. 4   c  illustrates a timing diagram of the diode illustrated in the solid state remote control switch illustrated  FIG. 3 ; 
       FIG. 4   d  illustrates a timing diagram of voltage before the solenoid illustrated in the solid state remote control switch illustrated in  FIG. 3 ; 
       FIG. 4   e  illustrates a timing diagram of the mechanical transition of switches  16 ,  26 , and  40  illustrated in the solid state remote control switch illustrated in  FIG. 3 ; 
       FIG. 5  illustrates an electrical schematic of a switching circuit incorporating certain aspects of a preferred controlled solenoid drive circuit; 
       FIG. 6   a  is a line voltage of the AC line for the schematic illustrated in  FIG. 5 ; 
       FIG. 6   b  illustrates a timing diagram of the controlled solenoid drive circuit of  FIG. 5 ; 
       FIG. 6   c  illustrates a timing diagram of the diode illustrated in the controlled solenoid drive circuit of  FIG. 5 ; 
       FIG. 6   d  illustrates a timing diagram of the LED  224  in the optical coupler  214 . 
       FIG. 6   e  illustrates a timing diagram of voltage across the solenoid illustrated in the controlled solenoid drive circuit of  FIG. 5 ; 
       FIG. 6   f  illustrates a timing diagram of the mechanical transition of switches  203  and  206  illustrated in the controlled solenoid drive circuit of  FIG. 5 ; 
   

   DETAILED DESCRIPTION 
   A schematic diagram of one remote control switch arrangement  220  incorporating aspects of the present invention is illustrated in  FIG. 5 . In one arrangement, remote control switch  220  comprises primary switch  201  and secondary switch with control circuit  222 . Various timing diagrams resulting from the remote control switch arrangement  220  illustrated in  FIG. 5  are illustrated in  FIGS. 6(   a - f ). 
     FIG. 5  illustrates a remote control switch  220  comprising a primary switch  201  and a secondary switch  220  with a solenoid control drive circuit  227 . In one arrangement, the primary switch  201  comprises mechanical switch and in an alternative arrangement, the primary switch  201  comprises a solid-state switch. In an alternative arrangement, where the primary switch  201  comprises a mechanical switch, the primary switch  201  comprises contacts  208  and is coupled to AC line  228  and an input to the secondary switch with control circuit  222 . 
   In one arrangement, secondary switch  222  comprises a first set of contacts  203 , a solenoid  205 , a second set of contacts  206 , and a solenoid control drive circuit  227 . As will be described in detail below, the various electrical components making up the solenoid control drive circuit  227  are selected so as to define a controlled or predetermined transition period after the primary switch  201  is transitions from a first to a second stable state. In other words, the various electrical components making up the solenoid control drive circuit  227  are pre-selected so as to achieve a controlled or predetermined contact closure delay after the primary switch  201  transitions contacts  208  from  229   a  to  229   b  and before the solenoid  205  is energized so they close solenoid contacts  206 . 
   For example and as illustrated in  FIG. 6   b , primary switch  201  of  FIG. 5  comprises contacts  208  that may reside in either an up position  229   a  or in a down position  229   b . According to one arrangement, the drive circuit  227  is coupled between the first set of contacts  203  and the solenoid  205  and preferably comprises the following components:
     diodes  210 ,  217  and diode  204  coupled to solenoid  205 ;   power SCR  218 ;   resistors  211 ,  216 ,  219 , and bleed resistor  220 ;   capacitors  212 ,  226 ;   optical coupler  214  comprising led  224  and optical triac  225     and threshold device  213  having a predetermined threshold or breakover level.
 
Preferably, the threshold device  213  may utilize different types of technologies including but not limited to such as: technologies as diacs, comparators, Zener diodes or other like solid-state components. Those of ordinary skill in the art will recognize that other electrical component configurations and/or selections may also be utilized.
   

   Referring now to  FIG. 5  and  FIG. 6   a , the contacts  208  for primary switch  201  begin in an up position  229   a  and travels to a down position  229   b . This contact travel begins traveling down at a time t 1    230 . As can be seen from  FIG. 6   a , contact travel commences at time t 1    230  and notably, this initial contact travel commences during a first portion  228   e  of a positive cycle of line voltage  228 . That is, contact travel does not commence when the AC line voltage  228  traverses the x-axis  231 . 
   When moveable contact  208  of primary switch  201  touches a lower (“normally open”) contact, contact  203  of secondary switch  222  passes a certain amount of current. For example, referring to  FIGS. 6   b  and  6   c , at time t 1    242 , while contact  208  first bounces  234  between a down position  229   b  and an up position  229   a , an initial small, amount of current proportional to staggered voltage  265  temporarily flows through node  223  and capacitor  212 . At the same time, an AC voltage appears at node  207 . As previously discussed with respect to the prior art control circuit schematic  10  illustrated in  FIG. 1 , the contact bounce of contacts of primary switch  201  creates an intermittent or temporary voltage spike at control circuit node  207 . As such, because of the biased nature of diode  210  illustrated in  FIG. 5 , first diode  210  will only pass various portions of negative half wave  261  of an input voltage  228  (a portion of voltage  228  in  FIG. 6   a ) to node  223 . Therefore, a signal at control circuit node  223  will represent a chopped negative half wave  261  of input voltage  228 . 
   Returning now to  FIG. 5 , as this chopped negative voltage  261  is being applied at node  223 , capacitor  212  will begin charging but will only charge during the negative period  228   a  of AC input voltage  228  and will be charged through resistor  211 . During a subsequent positive period  228   b  of an input AC voltage  228 , because of the capacitor&#39;s polarity, capacitor  212  will discharge. Preferably, capacitor  212  will discharge by way of a bleed resistor, such as bleed resistor  220 . In one preferred arrangement, bleed resistor  220  will have a resistance valued that is greater than the resistance values of resistor  211 . For example, in one preferred arrangement, resistor  220  may have a value of approximately 50 kiloOhms while resistor  211  may have a value of approximately 3 kiloOhms, however, other arrangements may also be used. Therefore, during a positive period of AC input voltage  228 , such as during positive period  228   b  of AC input voltage  228  of  FIG. 6 , capacitor  212  will maintain its stored charge. 
     FIG. 6   c  illustrates the voltage available at nodes  207  and  223  of  FIG. 5 . As illustrated in  FIG. 6   c , at time t 4    248 , a voltage across capacitor  212  will generally exceed a breakover voltage  264  of diac  213 . Such diac  213  is generally a bidirectional trigger diode that is designed specifically to trigger a triac or an SCR. Generally, such a diac will not conduct until a breakover voltage (such as diac breakover voltage  264 ) is reached. At such a breakover voltage point, the diac goes into avalanche conduction. At such a point, the diac  213  also exhibits a negative resistance characteristic, and the voltage drop across the diac snaps back, typically about 5 volts, creating a breakover current sufficient to trigger the triac or SCR. In one preferred arrangement, such a breakover voltage may comprise from generally about 5 to about 40 volts. As those of ordinary skill will recognize, other threshold device configurations with predetermined breakover voltages may also be utilized. For example, a threshold device may include some advanced features such as a feature that does not allow a threshold device turning into a conducting state if the line voltage is lower or greater than a particular voltage range specified for a particular solenoid. It provides a failure-free operation at low line condition and may prevent solenoid damage at a high line condition. 
   Therefore and as illustrated at time t 4    248  in the timing diagram  270  of  FIG. 6   d , once the breakover voltage  264  of diac  213  has been exceeded, diac  213  will turn into a conducting state and, in the arrangement illustrated in  FIG. 5 , this occurs at time t 4    248 . Preferably, breakover voltage  264  of diac  213  is chosen so as to provide a controlled or sufficient amount of time for primary switch  201  to complete or ride through any potential contact bounce or chatter that occurs when the contacts are moved from the first position  229   a  to the second position  229   b . For example, in one preferred arrangement, the diac breakover voltage  264  is predetermined and may be user defined so as to generally provide about 10 to generally about 50 milliseconds of time. In certain typical applications, such a predetermined timing delay will avoid potential contact bounce. In one preferred arrangement, diac breakover voltage  264  will occur during a negative half wave  228   c  of input voltage  228  (see  FIG. 6   a ), since capacitor  212  will have been charging during this period. 
   Once the diac  213  transitions from a non-conducting state to a conducting state, this diac&#39;s conductive state causes a discharge of current from a positive pole  215  of capacitor  212  via resistor  225  and LED  224  (preferably an optical coupler  214 ) to a negative pole  222  of capacitor  212 . Therefore LED  224  (of optical coupler  214 ) turns ON at time t 4    248 . This is illustrated in the timing diagram  270  of  FIG. 6   d . As shown in timing diagram  270  of  FIG. 6   d , LED  224  remains in an ON state  272  beginning at time t 4    248  until an LED current drops and diac  213  turns to an OFF state  273 . Diac  213  turns to an OFF state at time t 7    254  and is generally illustrated in  FIG. 6   e.    
   Optical triac  225  turns to its ON state at the same time t 4    248  and remains in this ON state at least until time t 5    250  where the positive half cycle  228   d  of line voltages  228  begins. Where this occurs along the line voltage  228  is important since the switch  201  will begin its transition at the start of a positive cycle  228   d  of line voltage  228  rather than in the middle of a positive cycle such as at  228   e  illustrated in  FIG. 6   a.    
   During a subsequent positive half wave of input voltage  228  comes at time t 5    250 , when optical triac  225  remains in a conducting state. Therefore, a positive potential from node  207  is present on resistor  216  and on optical triac  225 . Diode  217  thereby powers a gate  218   a  of a power SCR  218 . SCR  218  turns ON and conducts current via diode  204  to thereby energize solenoid  205 . Energizing solenoid  205  pulls in contact  206  to thereby energize the load  202 . Therefore, the solenoid drive circuit  227  illustrated in  FIG. 5  enables solenoid  205  to receive a complete positive pulse  228   d  ( FIG. 6   e ) of input voltage  228  rather than receive only some component thereof (such as occurs in circuit  10  of  FIG. 1 ). 
   Therefore, since solenoid  205  receives a complete positive pulse  228   d  of input voltage  228 , this allows for completing a mechanical transition of both switches  203  and  206  and this occurs at time t 6    252 . Mechanical transition of contacts  206  in  FIG. 5  is therefore achieved without the incomplete mechanical interruptions that can typically can occur when utilizing the remote control circuit  10  illustrated in  FIG. 1  and is generally explained by way of the timing diagrams illustrated in  FIGS. 2(   a - e ) and the solid state remote control circuit illustrated in  FIG. 3  and consequently explained by way of the timing diagrams illustrated in  FIGS. 4(   a - e ). Reducing such mechanical interruptions also reduces certain concerns that may also arise due to contact arcing and the consecutive overheating of such contacts that this contact may cause. 
   Preferably, a value of first capacitor  212  that is coupled to the threshold device  213  is selected to allow a sufficient enough charging time so as to complete any possible bounce of primary switch  201 . Therefore, any potential contact bounce will not affect switch transition. In one preferred arrangement, LED  224  (optical coupler  214 ) remains in an ON state or in a conducting state even after primary switch transition. That is, LED  224  (optical coupler  214 ) remains in an ON state or a conducting state until first capacitor  212  discharges via bleed resistor  209  to a lower threshold voltage of diac  213 , such as the diac lower threshold  260  illustrated in  FIG. 6   c.    
   In one preferred arrangement, respective values of first capacitor  212 , resistor  211  and resistor  209  are pre-selected so as to provide a controlled and predetermined charging and/or discharging time. Preferably, a charging time  292  (from t 2    244  to t 4    248 ) exceeds a maximum contact bounce time of the contacts  208  of primary switch  201 . 
   Discharging time  198  of first capacitor  212  contains essentially two time different periods: a first time period from t 4    248  to t 7    254 . Discharging time  198  also comprises a second time period defined as a timer period  232  extending from t 7    254  to about t 8    258 . In one preferred arrangement, the first period of time is greater than half a period or half-cycle of an AC line voltage  228 . In one preferred arrangement, first discharge period of time  294  should be approximately around 10- to about 50 milliseconds. Such a predetermined discharge period of time would be particularly advantageous where the primary switch  201  is utilized for a line voltage  228  comprising 50/60 Hz. Second period of time  296  shall also preferably exceed the electrical and mechanical transitions related to solenoid  205 . Preferably, this period should not exceed the minimal specified time between two consecutive switching operations. 
   Exemplary embodiments of the present invention have been described. Those skilled in the art will understand, however, that changes and modifications may be made to these embodiments without departing from the true scope and spirit of the present invention, which is defined by the claims.