Patent Publication Number: US-11662098-B2

Title: Gas safety shutoff

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. Nonprovisional patent application Ser. No. 17/077,629, filed Oct. 22, 2020, and issuing as U.S. Pat. No. 11,300,298, which is a continuation of U.S. Nonprovisional patent application Ser. No. 16/211,676, filed on Dec. 6, 2018, which issued as U.S. Pat. No. 10,830,449, which is a continuation of U.S. Nonprovisional patent application Ser. No. 15/167,797, filed May 27, 2016, which issued as U.S. Pat. No. 10,151,493, which claims the priority benefit of Provisional Patent Application No. 62/168,686, entitled “GAS SAFETY SHUTOFF,” filed May 29, 2015, the entirety of which are each fully incorporated herein by reference. 
    
    
     BACKGROUND 
     Grills or other cooking apparatuses use igniters to start flames. For gas grills, a valve disposed along a gas line is operated to control a flow of gas to a burner, and an igniter disposed downstream of the valve is operated to ignite gas flowing through an open valve to start a flame at the burner. 
     SUMMARY 
     A grill can include a safety shutoff apparatus for added safety. In some aspects of the subject technology, a safety shutoff can shut off a flow of gas in response to detection of a lack of flame at a burner using a flame sensor. In some implementations of the subject technology a flame sensor can include one or more components subject to wear, degradation, contamination, or a combination thereof (e.g., contamination of a sensor rod or a circuit board), which may impair functioning of the flame sensor, such as, for example, by causing a magnitude of a flame detection signal to drift over time, or diminishing reliability of the flame sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide further understanding and are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and together with the description serve to explain the principles of the disclosed embodiments. In the drawings: 
         FIG.  1 A  illustrates a block diagram of a grill apparatus according to example aspects of the present disclosure. 
         FIG.  1 B  schematically illustrates a grill apparatus according to example aspects of the present disclosure. 
         FIG.  1 C  illustrates a valve according to example aspects of the present disclosure. 
         FIG.  1 D  is an exploded view of the valve  110  of  FIG.  1 C . 
         FIG.  2    shows a flowchart of a process of automatically shutting off a gas valve according to example aspects of the present disclosure. 
         FIGS.  3 A- 3 D  show tables corresponding to normal operating states for a gas safety shutoff apparatus according to example aspects of the present disclosure. 
         FIG.  3 E- 3 I  show tables corresponding to additional operating states for the gas safety shutoff apparatus according to example aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one ordinarily skilled in the art that the embodiments of the present disclosure may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the disclosure. 
       FIG.  1 A  illustrates a block diagram of a grill apparatus  100 .  FIG.  1 B  schematically illustrates an example grill apparatus  100 .  FIGS.  1 C and  1 D  illustrate an example of a valve  110 . 
       FIG.  1 A  illustrates the grill apparatus  100  comprising the valve  110 , an igniter  120 , a flame sensor  140 , a control circuit  150 , an LED  130 , a gas supply  160 , a burner  170 , a transformer  154 , and a battery  152  according to example aspects. The grill apparatus  100  may correspond to a grill, or another appliance that utilizes flame. The gas supply  160  can comprise a source of combustible gas, such as, for example, a tank or continuous flow system. The grill apparatus  100  can comprise a single valve  110  for a single burner  170 , or can comprise multiple valves  110  for respective multiple burners  170 , each valve being independently controllable. For example, the grill apparatus illustrated in  FIG.  1 B  comprises four valves  110   a ,  110   b ,  110   c ,  110   d  for respective burners  170   a ,  170   b ,  170   c ,  170   d . Two views of the four valves  110   a ,  110   b ,  110   c ,  110   d  are shown in  FIG.  1 B . One view of the valves illustrates the connection of the valves to a gas feed system. The other view of the valves illustrates electrical connections between the valves, control circuits  150 , the battery  152 , and the transformer  154 . Although  FIG.  1 A  illustrates the igniter  120  as comprising the flame sensor  140 , in some aspects of the subject technology, the same combination of components (e.g., an electrode) can be operable to both ignite a flame and detect the presence of a flame. In some aspects of the subject technology, the igniter  120  and the flame sensor  140  can be independent, sharing no component between them. 
       FIG.  1 B  shows an example grill apparatus  100 . In  FIG.  1 B , the grill apparatus  100  comprises multiple burners  170 , including burners of different configurations, such as, for example, a sear burner  172  and a rotisserie burner  174 , The gas supply  160  ( FIG.  1 A ) is coupled to an inlet  180  of the gas feed system. The gas feed system can include pipes, hoses, and/or other apparatus for conducting the flow of gas. The gas feed system conducts gas from the gas supply  160  to each burner  170  through respective valves  110 . Each burner  170  is coupled to a respective igniter  120 . Each valve  110  is coupled to a respective control circuit  150  and LED  130 . The transformer  154  and the battery  152  are connected to each control circuit  150 . 
     The example valves illustrated in  FIGS.  1 A- 1 D  each comprise a handle  112  (e.g., a knob), a cam member  114 , a solenoid  116 , and a switch  118 .  FIG.  1 C  illustrates an example valve  110  including its solenoid  116  and valve handle  112 .  FIG.  1 D  is an exploded view of the valve  110  of  FIG.  1 C . As shown for example in  FIG.  1 D , the valve  110  can comprise a valve body  190 , an inlet  192 , and an outlet  194 . The valve can comprise trim, including one or more seats (which may be formed by the valve body), one or more valve members (e.g., plugs, balls, discs, etc.), and a stem  196 . The valve member(s) can seal against the seat(s) to close a gas passage through the valve. The stem  196  can protrude from the valve body  190 . The cam member  114  is attached to the stem  196  so that the stem moves with the cam member. The cam member  114  is attached to the handle  112  so that the cam member moves with the handle. 
     The valve  110  is connected to the gas supply  160 . The valve  110  allows gas from the gas supply  160  to flow through the valve when it is open, and prevents gas from flowing through the valve when it is closed. The solenoid  116  can comprise an electromagnet that holds open the valve  110  when a current is provided, such as a current of about 180 mA. However, in some implementations of the subject technology, the solenoid  116  when activated by a current can hold the valve  110  open, but is unable to open the valve  110  from a closed state. In other words, the valve  110  may be mechanically opened through the valve handle  112  then held open by the solenoid  116 , but cannot be pulled open by the solenoid alone. A valve comprising a solenoid is referred to herein as a solenoid valve. 
     The valve  110  is opened by physical manipulation (e.g., rotation, depression, or a combination thereof) of the valve handle  112  to mechanically open a passage through the valve. The position of the valve handle  112  can determine the extent to which the valve  110  is opened, to control a flow rate of the gas. In some implementations of the subject technology, the valve handle  112  is rotated counterclockwise while depressing it to open gas flow initially with depression not required for adjustment of the extent of gas flow thereafter. The valve handle  112  can be marked, for example, LO and HI, corresponding to a low flow rate, adjustable to a high flow rate. Manipulation of the valve handle  112  can move the cam member  114 , which can be connected directly to the handle  112  and/or to a shall (e.g., the stem  196 ) that is also connected to the valve handle  112 . The cam member  114  comprises a cam  198  that is positioned, when the valve is assembled, to interact physically with the switch  118  to selectively actuate it based on a position of the cam member  114  relative to the switch  118 . Sufficient movement (e.g., rotation) of the cam member  114  can close the switch  118 . While the valve  110  is open, such as any position from LO to HI, the switch  118  can be closed by virtue of the position of the cam member  114 . 
     The control circuit  150  can be an integrated circuit, and can comprise one or more sub-circuits. The control circuit  150  can comprise a single printed circuit board, or can be a master board with several slave boards. The control circuit  150  can include or be coupled to a power source. For example, the control circuit  150  can be powered by the transformer  154 , which can be as a 12 VDC, 5-8 Amp center-tapped transformer. Additionally or alternatively, the control circuit  150  can be powered by the battery  152 . In some implementations, the transformer  154  can trickle charge the battery  152 . The control circuit  150  can communicate electrically with the igniter  120 , LED  130 , flame sensor  140 , solenoid  116 , and switch  118 . 
     When the switch  118  is closed (activated), the control circuit  150  sends a current to the solenoid  116  of the valve  110 . The current can be a millivolt current sent to the solenoid  116  of the valve  110 . In  FIG.  1 B , solenoid control signals are sent through two wires, although in other implementations more or fewer wires can be used. The solenoid  116  holds the valve open under control of the control circuit  150  while the switch  118  is closed. 
     The control circuit  150  can power the LED  130 , so that it illuminates, when the switch  118  is activated, to indicate the attempt to light or ignite the burner. The LED  130  can be a 1.5 VDC blue LED, which begins flashing to indicate the ignition attempt. In other implementations, the LED  130  can be another color LED or other visual or audible indicator. 
     When the switch  118  is initially activated, the control circuit  150  can send an ignition current to the igniter  120 . The igniter  120  can be any igniter configured to ignite a burner. For example, the igniter can be a direct-spark igniter, a hot-surface igniter (e.g., a ceramic hot-surface igniter), or any other electrically powered ignition system. In certain implementations, the igniter  120  can also comprise the flame sensor  140 . In some such implementations, flame sensing can be inactive during application of ignition current to the igniter. For example, a detection signal, which can be an AC signal, can be continuously applied to the flame sensor  140 , e.g., by the control circuit  150 , to detect the presence or absence of flame (e.g., when an AC signal is rectified by a flame to a DC signal). In some implementations, the detection signal is not sent to the igniter, e.g., by the control circuit  150 , while the ignition current (e.g., a 12 VDC signal) is sent to the igniter. In some implementations, the detection signal and ignition current can be switched back and forth rapidly, e.g., by the control circuit  150 , to achieve near-simultaneous ignition and flame sensing. In some implementations, such as those wherein components of the igniter  120  and the flame sensor  140  are separate or discrete, the detection signal can be sent, e.g., by the control circuit  150 , to the flame sensor concurrently with application of ignition current to the igniter, e.g., by the control circuit  150 . 
     When the valve  110  is open (e.g., held open by a solenoid  116 ), the igniter  120  can ignite gas flowing toward the burner from the valve  110 . As a safety precaution, gas flow can be shut off if the gas does not ignite. For example, the igniter  120  can be on for a period, e.g., 5-6 seconds, then turned off for a period, e.g., 3 seconds, while presence or absence of a flame is detected. 
     In some implementations, presence or absence of a flame is detected by a flame sensor  140  by rectification of a detection signal passed through the flame sensor, which can be integrated partially or entirely with or discrete from the igniter  120 . In some implementations, the flame sensor direct current of the detection signal through a location where a flame may be present during normal burner operation. For example, the flame sensor can comprise an electrode positioned such that the location where a flame may be present during normal burner operation is intersected by an arc of current between electrode components. The flame sensor  140  can be activated, by sending the detection signal to the flame sensor, before ignition current is sent to the igniter  120 . For example, in response to the switch  118  being activated, the control circuit  150  can active the flame sensor  140 , and after a sensor activation period, such as 100 ms, the control circuit  150  can send an ignition current to the igniter  120 . Alternatively, the flame sensor  140  can be always on when the grill apparatus  100  is on. The control circuit  150  can continuously or intermittently monitor the detection signal from the flame sensor  140  through some or all of the process for igniting the corresponding burner. Additionally or alternatively, the control circuit  150  can continuously or intermittently monitor the detection signal from the flame sensor  140  after a process for igniting the corresponding burner has concluded. 
     A change in the detection signal can indicate the presence of flame, or successful ignition. In some implementations, the control circuit  150  monitors for sudden changes in the flame rectifier signal. For example, the detection signal can have a wave form when no flame is present, but flatten in response to flame rectification. In some implementations, presence or absence of a flame can be determined by the control circuit based on an absolute value of a parameter of the detection signal (e.g., voltage). Additionally or alternatively, presence or absence of a flame can be determined by the control circuit based on a change (e.g., a magnitude of change) of a value of a parameter of the detection signal (e.g., voltage). In some implementations, presence or absence of a flame can be determined by the control circuit based on a derivative of the detection signal over a period including at a time before ignition or before an ignition process being. 
     Advantageously, some implementations of the subject technology can detect presence or absence of a flame independently of an absolute threshold value of a parameter of the detection signal (e.g., voltage). In implementations wherein one or more component of the flame sensor  140  (e.g., such as portions of the switch  118 , the control circuit  150 , or a rod (e.g., of an electrode) protruding to a location where flame is expected to be present continuously or intermittently during use of a burner) can be worn, degraded, contaminated, or a combination thereof over time, altering characteristics of the components that may cause absolute values of the detection signal, in otherwise similar conditions, to drift. Thus, such wear, degradation, or contamination may cause inaccurate or unreliable determination of presence or absence of a flame based on an absolute value of a parameter of the detection signal, such as by determining whether an absolute value of a parameter of the detection signal passes a static threshold value. Degradation can be caused by, for example, rusting of materials and resistivity changes due to hot/cold cycles. Contamination can be caused by, for instance, salt, grease, or food contacting parts of the flame sensor  140 . In some aspects of the subject technology, by determining presence or absence of a flame based on identification of a change in the detection signal from before activating the igniter to a time during or after activating the igniter, rather than an absolute value, the effects of wear, degradation, contamination, or a combination thereof can be reduced. 
     For example, degradation to the flame sensor  140  can cause the absolute value of the detection signal received from the flame sensor to drift lower under otherwise similar circumstances. For example, a degraded flame sensor  140  may produce, when a flame is present, a detection signal having an absolute value that is below an absolute value threshold for detection based on flame rectification. On the other hand, even if an absolute value of a parameter of the detection signal drifts, a degraded flame sensor  140  can still produce a detection signal having a parameter that changes in absolute value between a time when a flame is not present to a time when a flame is present. Such a change in the detection signal can still be detected by the control circuit despite the drifting of absolute values. 
     While the ignition current is sent to the igniter  120 , the valve  110  is held open by the solenoid  116  for at least an ignition period, which can be 10 seconds. The flame sensor  140  continues to detect flame from a time before the ignition current is sent until at least a time during the ignition period. If presence of a flame is detected (e.g., rectification of the detection signal received from the flame sensor is identified) within the ignition period, the solenoid  116  remains active and the valve  110  remains open. In some implementations, the ignition current is applied to the igniter  120  for an entire predetermined ignition period, such as 3 seconds, even after the presence of a flame has been detected. In some implementations, the flame sensor continuously monitors the status of flame following detection of the presence of a flame, the end of an ignition period, or both. The LED  130  is updated to a normal status, which can be solid blue. The burner is then in a normal operation. 
     In some implementations of the subject technology, if the presence of a flame is not detected (e.g., rectification of the detection signal received from the flame sensor is not identified) within the ignition period, the valve  110  is closed. The valve  110  can be closed by the control circuit  150  ceasing to deliver current to the solenoid  116  of the valve  110 . In some implementations, the control circuit  150  controls the LED  130  to indicate a fail status. For example, the control circuit  150  can send a signal to the LED or cease delivery of a signal to the LED. A fail status can be indicated by a change to the state of the LED, such as for example, by changing form a continuously illuminated or unilluminated state to a blinking light. The color of the light can additionally or alternatively be altered, e.g., changed from blue to red. 
     In a failed ignition state gas has been flowing through a valve for a specified period of time without detection of the presence of a flame, or with detection of a flame of insufficient stability, at the burner. In some implementations, if the control circuit  150  detects a failed ignition state (e.g., by determining that the detection signal from the flame sensor  140  is not rectified, insufficiently rectified, or consistency of rectification is insufficient) for an entire duration of the ignition period or more, the control circuit  150  can close the valve  110  and update a status of the LED  130  to indicate ignition failure. If the control circuit  150  detects the presence of flame within the ignition period, the control circuit  150  can update a status of the LED  130  to indicate normal operational status. In some implementations, the control circuit  150  thereafter monitors, continuously or at intervals, a state of the flame. 
     In a flame failing state gas has been flowing through a valve and the presence of a flame was previously detected, or detected to be of sufficient stability, and during a period in which the valve has remained open since then a predetermined amount of time has elapsed without detection of the presence of a flame, or with detection of a flame of insufficient stability, at the burner. In some implementations, if the control circuit  150  detects a failing state (e.g., by determining that the detection signal from the flame sensor  140  is not rectified, insufficiently rectified, or consistency of rectification is insufficient) for a predetermined period of time during normal operation, the control circuit  150  can re-energize or otherwise reactivate the igniter  120 . The control circuit  150  can update a state of the LED  130  to indicate performance of an attempt at re-ignition, such as flashing blue as described above. If the control circuit  150  does not detect successful ignition (e.g., by determining that the detection signal from the flame sensor  140  is not rectified, insufficiently rectified, or consistency of rectification is insufficient) for a predetermined period, the control circuit  150  can close the valve  110  and update a status of the LED  130  to indicate ignition failure. If the control circuit  150  detects the presence of flame within the predetermined period, the control circuit  150  can update a status of the LED  130  to indicate normal operational status. In some implementations, the control circuit  150  thereafter monitors, continuously or at intervals, a state of the flame. 
     If the control circuit  150  detects a failed ignition state or a failed re-ignition state, the control circuit  150  can close the valve  110  and update the LED  130  to indicate a fail status, and the control circuit  150  locks out the valve  110  for at least a lockout period, such as 30 or 45 seconds, in which the control circuit  150  will not activate the solenoid  116 , to allow the released gas to dissipate. 
       FIG.  2    shows a flowchart  200  of an example process for operating a grill apparatus  100  according to some aspects of the subject technology. The example process of  FIG.  2    includes a process for automatically shutting off a gas valve of a burner for a grill according to example aspects.  FIGS.  3 A- 3 I  show tables corresponding to various states during the process illustrated by  FIG.  2    according to example aspects. At state  302 , shown in the table of  FIG.  3 A , the burner starts with (a) a switch (e.g., switch  118 ) in an off state, (b) the valve (e.g., valve  110 ) being off such that gas does not flow through the valve, (c) the solenoid (e.g., solenoid  116 ) being off, (d) the igniter (e.g., igniter  120 ) off, (e) the burner being off such that no flame is present, and (f) the sensor (e.g., flame sensor  140 ) is not indicating the presence of a flame. 
     In state  304 , shown in the table of  FIG.  3 B , the valve has been mechanically opened (block  210 ), which activates the switch (block  212 ) to an on state. The control circuit  150  begins blinking the LED (e.g., LED  130 ) (block  214 ) to indicate performance of an ignition attempt. The control circuit  150  activates the igniter (block  216 ) and applies a current to activate the solenoid (block  218 ) with a 3 second delay. In state  304 , shown in the table of  FIG.  3 C , the burner is off and no flame is detected by the control circuit  150  based on a signal received from the sensor. The control circuit  150  continues to monitor for the flame (block  220 ) based on a signal received from the sensor. 
     When the control circuit  150  detects a flame at state  306 , the burner is on. The control circuit  150  applies a 3 second delay before shutting off the igniter (block  222 ) at state  308 , shown in the table of  FIG.  3 D . The control circuit  150  continuously powers (turns on) the LED (block  224 ) to indicate the burner is on. 
     However, if the control circuit  150  does not detect the presence of flame for at least 3 seconds (block  226 ) then, at state  310 , shown in the table of  FIG.  3 E , the control circuit  150  determines that the burner is failing and causes the LED to blink (block  226 ) to indicate ignition attempt, and turns on the igniter (block  228 ) at state  312 , shown in the table of  FIG.  3 F . 
     The control circuit  150  monitors for presence of a flame for at least 10 seconds (block  230 ) based on a signal received from the sensor. If the control circuit  150  detects the presence of a flame within the 10 seconds, then after applying a 3 second delay the control circuit  150  shuts off the igniter (block  232 ), and continuously powers (turns on) the LED to indicate the burner is on (block  234 ) to reach a pass state  314 , shown in the table of  FIG.  3 G . If the control circuit  150  fails to detect the presence of a flame within the 10 seconds based on the signal received from the sensor, the control circuit  150  deactivates the solenoid to close the passage through the valve (block  236 ) at the fail state  316 , shown in the table of  FIG.  3 H , although the handle of valve can still be in an ON position. The control circuit  150  powers the LED so that it begins blinking (and may change the color to red) to indicate failure and a need for reset. In certain implementations, if the control circuit  150  deactivates the solenoid valve to close the passage through the valve, the control circuit  150  keeps the solenoid deactivated for at least a purge duration, such as 45 seconds, to allow any built up gas to purge. If a handle of the valve is still in the ON position, the handle can be returned to an OFF position, e.g., physically returned by a user. At the reset state  318 , shown in the table of  FIG.  3 I , the switch is off, the valve is closed, the solenoid is off, the igniter is off, the burner is off, and the sensor is not indicating the presence of a flame. The reset may place the burner back to the initial setting (e.g., state  302 ). 
     Although various aspects, features, and exemplifying embodiments of the subject technology have been described with reference to grills, the subject technology also can be practiced with other cooking appliances, such as ovens and stoves for example, in the place of the referenced grills. 
     As used herein, the phrase “at least one of” preceding a series of items, with the terms “and” or “or” to separate any of the items, modifies the list as a whole, rather than each member of the list (i.e., each item). The phrase “at least one of” does not require selection of at least one item; rather, the phrase allows a meaning that includes at least one of any one of the items, and/or at least one of any combination of the items, and/or at least one of each of the items. By way of example, the phrases “at least one of A, B, and C” or “at least one of A, B, or C” each refer to only A, only B, or only C; any combination of A, B, and C; and/or at least one of each of A, B, and C. 
     A reference to an element in the singular is not intended to mean “one and only one” unless specifically stated, but rather “one or more.” All structural and functional equivalents to the elements of the various configurations described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and intended to be encompassed by the subject technology. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the above description. 
     While this specification contains many specifics, these should not be construed as limitations on the scope of what can be disclosed, but rather as descriptions of particular implementations of the subject matter. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features can be described above as acting in certain combinations and even initially disclosed as such, one or more features from a disclosed combination can in some cases be excised from the combination, and the disclosed combination can be directed to a subcombination or variation of a subcombination. 
     Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing can be advantageous. Moreover, the separation of various system components in the aspects described above should not be understood as requiring such separation in all aspects, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
     The subject matter of this specification has been described in terms of particular aspects, but other aspects can be implemented and are within the scope of the following disclosure. For example, the actions recited in the disclosure can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing can be advantageous. Other variations are within the scope of the disclosure. 
     Illustration of Subject Technology as Clauses 
     Various examples of aspects of the disclosure are described as numbered clauses (1, 2, 3, etc.) for convenience. These are provided as examples, and do not limit the subject technology. Identifications of the figures and reference numbers are provided below merely as examples and for illustrative purposes, and the clauses are not limited by those identifications.
     Clause 1. A system for igniting a grill, the system comprising:   

     a solenoid valve comprising a switch and a handle, the switch actuated by manipulation of the handle, the solenoid valve configured to be held open by a current; 
     a flame rectification sensor configured to change a flame detection signal, 
     an igniter; and 
     a control circuit electrically coupled to the solenoid valve, the switch, and the flame rectification sensor, the control circuit configured to selectively send the current to the solenoid valve when the switch is closed, to determine presence of a flame based on the change to the flame detection signal, and to close the solenoid valve when the control circuit does not detect the presence of a flame after an ignition of the igniter.
     Clause 2. The system of clause 1 or any of the clauses, wherein the control circuit is configured to determine presence of a flame by comparing the flame detection signal before the ignition and the flame detection signal after the ignition.   Clause 3. The system of clause 1 or any of the clauses, wherein the control circuit is configured to determine the presence of a flame by determining a derivative of a flame rectifier signal over a period from before the ignition to after the ignition.   Clause 4. The system of clause 1 or any of the clauses, wherein the flame rectification sensor comprises a spark igniter.   Clause 5. The system of clause 1 or any of the clauses, wherein the igniter is configured to ignite a gas using a hot ceramic surface.   Clause 6. The system of clause 1 or any of the clauses, further comprising a cam member mechanically coupled to the handle, wherein actuating the handle moves a cam of the cam member to close the switch.   Clause 7. The system of clause 6 or any of the clauses, wherein the cam is configured to hold the switch closed when the handle of the solenoid valve is in an open position.   Clause 8. The system of clause 1 or any of the clauses, wherein the control circuit comprises a power supply circuit.   Clause 9. The system of clause 1 or any of the clauses, wherein the control circuit comprises a center-tapped transformer.   Clause 10. The system of clause 1 or any of the clauses, wherein the solenoid valve cannot be opened by the current.   Clause 11. A method for igniting a grill, the method comprising:   

     actuating a handle to mechanically open a solenoid valve, and to move a cam configured to close a switch when the handle is moved to open the solenoid valve, the cam configured to hold the switch closed when the handle is in an open position; 
     when the switch is closed, selectively sending a current to the solenoid valve to hold the solenoid valve open; 
     in response to the switch closing, sending an ignition current to an igniter to start ignition of the igniter; 
     determining whether a flame is present based on a change to a flame detection signal from a flame rectification sensor; and 
     after the presence of the flame has been determined, monitoring the flame detection signal for continued presence of the flame.
     Clause 12. The method of clause 11 or any of the clauses, wherein determining whether a flame is present comprises reading the flame detection signal before the ignition and reading the flame detection signal after the ignition.   Clause 13. The method of clause 11 or any of the clauses, wherein determining whether a flame is present comprises determining a derivative of a flame detection signal over a period from before the ignition to after the ignition.   Clause 14. The method of clause 11 or any of the clauses, further comprising closing the solenoid valve in response to detecting that no flame is present after a predetermined period after commencing sending the ignition current to the igniter.   Clause 15. The method of clause 14 or any of the clauses, wherein closing the solenoid valve comprises ceasing delivery of current to a solenoid of the solenoid valve.   Clause 16. The method of clause 14 or any of the clauses, further comprising changing an LED to flash a warning color in response to detecting that no flame is present after a predetermined period after commencing sending the ignition current to the igniter.   Clause 17. The method of clause 11 or any of the clauses, further comprising:   

     determining that flame is no longer present; and 
     in response to determining that flame is no longer present, sending an ignition current to the igniter.
     Clause 18. The method of clause 11 or any of the clauses, further comprising closing the solenoid valve for at least a lockout period.   Clause 19. The method of clause 11 or any of the clauses, further comprising commencing flashing of an LED in response to actuation of the handle to mechanically open the solenoid valve.   Clause 20. The method of clause 11 or any of the clauses, further comprising continuously powering an LED in response to detection of the presence of a flame.   

     In an aspect, any of the clauses herein may depend from any one of the independent clauses or any one of the dependent clauses. In an aspect, any of the clauses (e.g., dependent or independent clauses) may be combined with any other one or more clauses (e.g., dependent or independent clauses). In an aspect, a clause may include some or all of the words (e.g., steps, operations, means or components) recited in a sentence, a phrase or a paragraph. In an aspect, a clause may include some or all of the words recited in one or more sentences, phrases or paragraphs. In an aspect, some of the words in each of the clauses, sentences, phrases or paragraphs may be removed. In an aspect, additional words or elements may be added to a clause, a sentence, a phrase or a paragraph. In an aspect, the subject technology may be implemented without utilizing some of the components, elements, functions or operations described herein. In an aspect, the subject technology may be implemented utilizing additional components, elements, functions or operations. 
     In an aspect, any methods, instructions, code, means, logic, components, blocks, modules and the like (e.g., software or hardware) described or recited in the clauses herein can be represented in drawings (e.g., flow charts, block diagrams), such drawings (regardless of whether explicitly shown or not) are expressly incorporated herein by reference, and such drawings (if not yet explicitly shown) can be added to the disclosure without constituting new matter. For brevity, some (but not necessarily all) of the clauses/descriptions are explicitly represented in drawings, but any of the clauses/descriptions can be represented in drawings in a manner similar to those drawings explicitly shown. For example, a flow chart can be drawn for any of the clauses or sentences for a method such that each operation or step is connected to the next operation or step by an arrow. In another example, a block diagram can be drawn for any of the clauses or sentences having means-for elements (e.g., means for performing an action) such that each means-for element can be represented as a module for element (e.g., a module for performing an action).