Variable control switch

The present invention is a variable control switch. In particular, it is a control switch with modifiable variables for activation and deactivation of primary and secondary devices. The control switch has an input plug and two output plugs. The control switch has a sensing circuit connected between the input plug and two output plugs and has an output comprising DC voltage varying proportionally to the current passing between said first and second output plugs. The sensing circuit is connected to a microcontroller unit that controls current to the first or second outputs based on a set of pre-determined variables, including a termination threshold.

BACKGROUND ART

Woodshops, job sites, and machine shops, as well as other shops and locations, often operate multiple devices on the same circuit and circuit breaker. For example, power tools are often used in conjunction with a wet/dry vacuum for ventilation and dust-control purposes. However, these devices often start with significant current spikes that, if both devices are activated close in time, can trip the circuit breaker and cause the power to be cut off to both devices. Thus, power controller circuits, such as that disclosed in U.S. Pat. No. 7,341,481, are used to regulate current to both devices to prevent tripping the common circuit breaker. However, these power controller circuits can be imprecise or lack fine control for the variety of devices and situations that can occur in a given work environment. Thus, a switch that is more flexible for a variety of situations and variables is needed.

SUMMARY OF THE INVENTION

The present invention is a variable control switch. In particular, it is a control switch with modifiable variables for activation and deactivation of primary and secondary devices. The control switch has an input plug and two output plugs. The control switch has a sensing circuit connected between the input plug and two output plugs and has an output comprising DC voltage varying proportionally to the current passing between said first and second output plugs. The sensing circuit is connected to a microcontroller unit that controls current to the first or second outputs based on a set of pre-determined variables, including a termination threshold.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following paragraphs, the present invention will be described in detail by way of example with reference to the attached drawings. Throughout this description, the preferred embodiment and examples shown should be considered as exemplars, rather than as limitations on the present invention. As used herein, the “present invention” refers to any one of the embodiments of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “present invention” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s). The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the general principles of the present invention have been defined herein specifically to provide a variable control switch.

Referring now toFIG.1, a preferred embodiment of the invention is shown, namely a control switch that turns power on and off to a secondary device, e.g. a wet/dry vacuum or ventilation system, based on a variety of variables such as electrical current flowing to a primary device, e.g. a power tool. The embodiment shown inFIG.1is an external plug adapter600to plug into an AC outlet (not shown) with a primary output610and a second output620. However, alternate embodiments can include a control switch embedded directly into primary devices, e.g. saws or other power tools, or secondary devices, e.g. wet/dry vacuums.

Referring now toFIG.2, a block diagram of a preferred embodiment of the invention for use with AC (alternating current) power supplies is shown. For reference purposes, the diagram shown inFIG.2can be broken down into various sections based on function.

Referring now toFIG.3, a preferred embodiment of the power conversion section100fromFIG.2is shown. Typically, the AC line voltage enters the circuit and passes through a rectifier to create a high voltage DC. The high voltage DC is filtered by an input bulk capacitor. The high voltage DC feeds the input to a non-isolated buck regulator control IC. The buck regulator IC switches at a proportional duty cycle to generate a lower DC voltage, which is typically at a 10:1 ratio. The output voltage DC is regulated at a higher voltage for peripheral components within the system. This voltage is fed to DC regulator section20.

Referring now toFIG.4, a preferred embodiment of the DC (direct current) regulator section20of the diagram inFIG.2is shown. DC voltage fed from section10(shown inFIG.9) passes through resistor R6and is filtered before powering the linear regulator integrated circuit (IC) U1. This regulator U1is preferably 36V input to fixed 5V output at 100 mA maximum load. The output from U1is fed to MCU section30.

Referring now toFIG.5, a preferred embodiment of the MCU (microcontroller unit) section30of the diagram inFIG.2is shown. The DC regulator section20preferably has 5V to power the MCU. The MCU monitors three input logic level sensors from three switches with switch states. Each level is high or low depending upon the switch state. The switch state will give 2 sensing levels, depending upon the firmware for the MCU. The input sensing resolution is preferably 10 bits. The following preferred sensing levels are defined:

Referring now toFIG.6, a preferred embodiment of the current sensing sections40aand40bfrom the diagram inFIG.2are shown. In section40a, AC current passes through current transformers (CT) T2and T3and converts the equivalent primary current to the secondary output in section40b. Current1and Current2are then fed to section20after signal filtering. Current1represents the equivalent current passing through the switch outlet Line1in section40a. Current2represents the equivalent current passing through the switched outlet Line2in section40a.

Referring now toFIG.7, a preferred embodiment of the AC voltage-sensing section50from the diagram inFIG.2is shown. AC voltage is divided down to a lower level for the MCU in section20to read the equivalent AC voltage on the line. The AC voltage is coupled using a capacitive voltage divider circuit, similar to section10. The MCU can preferably read a 0-4V level.

Referring now toFIG.8, a preferred embodiment of the relay switching section60from the diagram inFIG.2is shown. RLY1(or contact1) can disconnect the switched output Line1. RLY2(or contact2) can disconnect the switched output Line2. RLY1and RLY2are controlled by MCU section20. It should be noted that multiple relay or contact configurations are possible. For example, Single Pole Single Throw (SPST) or Single Pole Double Throw (SPDT), or other options such as DPST, DPDT and Solid State Relays are available. In general, the term “contact” or “relay” is used. Moreover, it is possible to use the present invention to actuate a 120 Vac Electro-Mechanical Relay to control a 208 Vac 3-Phase to use the device as an intelligent switch.

Referring now toFIG.15, another embodiment of the invention is shown for use with a non-isolated high voltage Buck controller power supply. Preferably, the circuit operates with an output regulated 12V at 200 mA. Again, for reference purposes, the diagram shown inFIG.15can be broken down into various sections based on function. Referring back toFIG.3, a preferred embodiment of the AC input isolated output section100is shown. AC line voltage enters the circuit and is rectified to a high voltage DC that is filtered and then switched at a high frequency using a PWM (pulse width modulation) signal.

Referring now toFIG.10, a preferred embodiment of the AC voltage sensing sections200aand200bare shown from the diagram inFIG.15. AC line voltage is preferably sensed through an optocoupler U1. This DC equivalent voltage is fed through the resistor divider circuitry in section200band then to the MCU section300.

Referring now toFIG.11, a preferred embodiment of the MCU section300is shown from the diagram inFIG.15. Section100powers the MCU section300. The MCU monitors three input logic level sensors from three switches. The switch state will preferably give 2 sensing levels, depending upon the firmware for the MCU. The input sensing resolution is preferably 8 bits. The following sensing levels are defined as follows:

Referring now toFIG.12, a preferred embodiment of the current sensing sections400aand400bare shown from the diagram inFIG.15. AC current passes through CT's T1and T2and converts the equivalent primary current to the secondary output in section400a. Current1and Current2are then fed to section300after signal filtering in section400b. Current1represents the equivalent current passing through the switch outlet Line1in section400a. Current2represents the equivalent current passing through the switched outlet Line2in section400a.

Referring now toFIG.13, a preferred embodiment of the relay switching section500is shown from the diagram inFIG.15. RLY1disconnects the switched output Line1. RLY2disconnects the switched output Line2. RLY1and RLY2are controlled by MCU section200.

Accordingly, using the diagrammed embodiments shown inFIG.2orFIG.15, a variable control switch, such as the embodiment shown inFIG.1, can turn power on and off to a secondary device, e.g. a wet/dry vacuum or ventilation system, based on a variety of variables such as electrical current flowing to a primary device, e.g. a power tool. The preferred variables (monitored by the switch for powering on or shutting down the primary and secondary devices) controllable by the user are as follows:

a) Current draw from the secondary device;

b) Actuation threshold of the primary device;

c) Startup delay for the secondary device;

d) Termination threshold for the primary device;

e) Normal operating current of the secondary device;

f) Overload delay for the secondary device;

g) Restart delay for the secondary device;

h) Shutoff delay for the secondary device; and,

i) Combined (for both primary and secondary devices) current limit.

Referring now toFIG.14, a schematic of a preferred embodiment of the invention using two relays is shown. In particular, controller300is preferably a microprocessor-based unit. Preferred microprocessors include Attiny13A, Attiny24A and Atmega128. The controller300preferably controls a variety of variables and/or functions. For example, the controller300preferably controls a trip level setting301, e.g. a current level set by an open switch for one level and closed for another level (or software configurable). The controller300preferably controls a time delay setting302, e.g. a delay time set by an open switch for one level and another level by a closed switch (or software configurable.) The controller300preferably controls a bypass setting303, e.g. a bypass switch, preferably open for normal operation and closed for bypass of the controller300(or software configurable). The controller300preferably controls a programming mode304, e.g. whereby the controller300enters programming mode (as described below) or receives data through a variety of connectors such as serial cables, USB ports or other connectors. The controller300preferably has an auto learn mode305. This mode305is used to place the invention into a mode where current settings/current sensed is stored into memory. The controller also preferably has a host/device mode306, preferably where the present invention is set as the “master unit” and makes decisions and sends commands to connected devices and/or other control units. The controller300preferably has an auxiliary drive307, e.g. where the present invention can drive devices having a control voltage range of 0-5V DC and a current range from 0-500 mA such as industrial machine indicators, horns or electro-mechanical relays.

Referring now toFIG.29, a rear view of the embodiment shown inFIG.1is shown. The switch600preferably has a rear panel630with an opening that allows access to a set of dip switches640. By manipulating the dip switches640, the user is able to set/control the variables for activation and deactivation of the switch600. Alternatively, dials, potentiometers or other types of switches can be used in lieu of the dip switches640. Another alternative is that the variables for switch control, e.g. activation and deactivation, can be entered/saved directly to the MCU unit, e.g.30or300. For example, the variables can be saved in firmware for the MCU unit, e.g. via a serial cable. These variables can be manipulated to account for the variety of primary and secondary devices (and their associated voltages and currents) that can be connected to the switch600. Thus, if a switch is embedded in a device with known variables, e.g. a known amperage draw, the variables can be more precisely set in software to optimize performance for the specific device.

Referring now toFIG.16, a graph of a typical device's current draw over time is shown. At actuation, the current draw “spikes” upward (also known as “inrush current”) and then settles to an “operating current.” When the device is shutdown, the current declines to zero.FIG.17divides the cycle into different phases: the startup phase, the normal operating phase and the shutdown phase.

One variable that can be used by the switch is “actuation threshold.” As shown inFIG.18, when the current to a device passes a particular level, the switch identifies the connected device as “actuated.” Similarly, when the current goes below that actuation threshold, the device is “deactivated.” Once the actuation threshold is passed by the primary device, the secondary startup delay begins. As shown inFIG.19, once the secondary startup delay concludes, the secondary device is activated by the switch (as shown inFIG.20), thus delaying a current spike from the secondary device and possibly tripping a circuit breaker. Similarly, once the primary device current passes below the actuation threshold, the secondary shutoff delay begins. At the end of the secondary shutoff delay, the secondary device is shutdown. This secondary shutoff delay allows the secondary device, such as a vacuum or ventilation system, to continue to operate while the primary device is shutting down.

Referring now toFIG.21, the actual current draw during the normal operating phase is the sum of the primary device current draw and the secondary device current draw. However, on occasion, the primary or secondary device can have a current spike. For example, as shown inFIG.22, the primary device's current can spike, e.g. a saw blade binds, such that when added to the current draw of the secondary device a circuit breaker may be tripped shutting down all current to the switch and devices. However, a termination threshold can be established for the switch based on the standard operating current of the secondary device. The termination threshold is preferably the difference between a circuit breaker limit and the standard operating current of the secondary device (seeFIGS.23and24.) Thus, when the actual current draw exceeds the termination threshold, the secondary device can be shutdown before a circuit breaker is tripped. As shown inFIG.25, once the secondary device is shutdown by the switch and current descends below the termination threshold, a restart delay will occur and then the switch will activate the secondary device again. Thus, the circuit breaker limit can be avoided and operation of the devices can continue without excessive delay.

The variable “termination threshold (TT)” can be described in greater detail as follows. TT is a value of electrical current measured in amps. This value is determined by taking the total current limit of the electrical circuit where the present invention is used and subtracting the normal operating current of a secondary device, e.g. a shop vacuum. Thus, the termination threshold is the total amount of current available that a primary device, e.g. a table saw, could draw from the circuit while the secondary device is running without exceeding the total current limit of the electrical circuit.

There are several ways to set the TT value for the present invention. One embodiment allows for manual adjustment. For example, using variable rotation switches, the user can set the value of the operating current of a secondary device as well as a separate switch to set the value of the current limit of the electrical circuit (usually 20 amps.) Software in the present invention used by the MCU can then calculate the TT value as the circuit limit less the secondary device operating current level.

Another embodiment allows for manual adjustment as well. Using variable rotation switches, the user can set the TT value for the present invention directly, which would be determined by having the user perform the calculation described above (electrical circuit limit less operating current of the secondary device.)

Another embodiment allows for semi-automatic adjustment of the TT value. After setting the electrical circuit limit (preferably a default 20 amps), the user would put the present invention into a “programming” mode, e.g. by depressing a switch or by other method. Once in the programming mode, the user would plug the secondary device into the primary port and turn the secondary device on. The present invention would then measure the current draw of the secondary device and, after a pre-determined time or a continued measurement of the same current draw level (which would indicate that the stabilized operating current level had been reached), the present invention would calculate the TT value (by subtracting the measured secondary current level from the electrical circuit limit) and store this value and indicate that the programming mode is completed (e.g., by changing an LED from blinking red to green). If the user wants to use a new or different secondary device, the user would put the present invention back into programming mode and repeat this procedure to store a new value in memory.

Another embodiment would allow for a fully automatic setting of the TT value. This embodiment would have a default current limit of 15 amps. This embodiment would then measure the current draw of both a primary device and a secondary device. When the combined currents of the two devices exceed the current limit, the secondary device would shut off for a pre-determined amount of time and then restart. The user would be able to adjust the current limit by, for example, turning dip switches or rotary switches to allow settings between 10 and 20 amps or between 15 and 25 amps. This would allow the user to match the settings to the particularities of their own electrical circuit and equipment. In this embodiment, the TT value is a dynamic value rather than a stored value and it is determined by subtracting the current draw of the secondary device from the total current limit set for the invention. This can also operate by tracking the total current draw of both devices and comparing this value against the total current limit.

The TT value is used to allow the present invention to selectively turn off the secondary device when the current draw of the primary device exceeds the TT value and therefore avoid overloading of the electrical circuit/tripping the circuit breaker. The current draw of a primary device can spike for a number of reasons, such as when a saw blade binds up against wet or green wood. By turning off a secondary device in this situation, the primary device has the full amount of current available on the electrical circuit to preferably “power through” the cause of the spike (or at least provide the user with the ability to stop the primary device and restart it)—without causing the circuit breaker to trip, which would require the user to go to the electrical panel and reset the circuit breaker.

Other variables can be detected and used by the present invention. For example, “Total Current Limit” is the amount of current flowing through the invention (to both the primary and secondary devices) and is measured by using two current-sensing transformers.

“Overload Delay” is the amount of buffer time during which a primary device is allowed to exceed TT before a secondary device is shut off. Circuit breakers typically have their own internal buffer and the Overload Delay could have a similar buffer to allow for short current spikes that would not trip the circuit breaker. This is an optional variable and is not required, e.g. the Overload Delay can be set to zero—meaning a secondary device will shut off immediately once the current draw of a primary device reaches the TT value.

Another variable that can be detected and used by the present invention is “Restart Delay.” Restart Delay is the amount of waiting time that will elapse after the current draw of a primary device has dropped back to/below the TT value before turning a secondary device back on. The primary reason for Restart Delay is to allow the current level of a primary device to drop down enough so that the inrush current level spike created when turning a secondary device back on will not exceed the circuit level and trip the circuit breaker. This option is a preferred method for determining when a secondary device will turn back on.

Another variable that can be detected and used by the present invention is “Restart Current Level.” Restart Current Level is a different current level that a primary device must drop to before a secondary device will turn back on. The Restart Current Level is TT less an additional amount of current. This allows a current spike when a secondary device is turned on to avoid tripping a circuit breaker. This is another option in lieu of the Restart Delay described above.

Restart Delay and Restart Current Level can be used together such that the current draw of a primary device would have to drop to or below the Restart Current Level and then, after the Restart Delay, a secondary device could restart.

The programming mode of the present invention described above would allow a user to measure and capture the inrush current level of a secondary device, e.g. a shop vacuum, as well as the stabilized operating current. With the inrush current level determined, the present invention could set the Restart Current Level as the TT value less the inrush current level of a secondary device. This would be a preferred way to allow for difference between inrush current levels of various secondary devices.

One embodiment that uses the Termination Threshold variable would preferably be static in nature. Accordingly, the available amperage for a primary device is set (and preferably stored in memory). Such a setting can be done in a variety of ways but basically the normal operating current of a secondary device is deducted from the overall circuit limit and this leaves the available power tool current. This option will preferably be used when the present invention is integrated into a device as the operating characteristics of the device (e.g. a shop vacuum) will be known and established so it can be stored in memory on the present invention.

Another embodiment that uses the Termination Threshold variable would preferably be dynamic in nature. Accordingly, the amperages of both a primary device and a secondary device are read and monitored continuously by the present invention. When the combined amperage of both devices exceeds the overall circuit limit (within certain tolerances), then the secondary device is shut down until there is enough available current to run it (the “normal operating current” levels of both the primary and secondary devices can be established dynamically each time the device is used or as described above).

Another embodiment of the invention preferably has a safe restart function. The function prevents a tool, or any other electrical device that is plugged into the primary output of the invention, from starting up inadvertently if the tool was left ON and there was a power failure. Some tools have locking ON switches (such as routers and table saws) and the safe restart function will provide additional safety to users by preventing such tools plugged into the primary output of the invention from restarting automatically after the resumption of power after a power failure, thus avoiding potential injury.

The invention described above has sensitive current measuring capabilities and also the ability to react quickly to various inputs due to the presence of microprocessor or MCU. The embodiment with safe restart function preferably uses additional software and a second relay on the primary output circuit, e.g. where the TOOL is energized. The software preferably runs an initial “Safe Restart Safety” function each time the invention is powered on. This function preferably measures the amount of current flowing to the primary output and, if any current is detected (which would indicate the TOOL is switched on), then the primary output will be turned off (by opening up the TOOL relay). This safe restart function will happen nearly “instantaneously”—preventing enough current to flow to the tool to actually turn on the tool itself. In this application, “instantaneously” is preferably less than 1 millisecond (ms). The TOOL or primary output relay will remain open until the invention is re-energized (at which point the safe restart function will run again). An optional indicator light on the invention can show the user (e.g. a flashing LED) if the primary output is “ON.”

There are at least three (3) ways for the invention to resolve the safe restart open relay condition:

1) The invention runs a continuous loop in the software for some predetermined period (e.g. every 8.33 milliseconds) and, once no current draw is detected from the tool, the MCU will close the relay and power will flow to the tool. This safe restart function is only run when the invention is first energized so it will not repeat the function as long as the invention remains energized once it has successfully passed the safe restart test/function;

2) The user unplugs the invention from a power source and then plugs it back into a power source if the safe restart function has opened up the relay that powers the TOOL; or,

3) The invention also preferably has a “reset” button to allow the safe restart function to be run without requiring the invention to be unplugged from a power source.

Referring now toFIG.28, a preferred embodiment of the circuit for the second relay for the safe restart function is shown. The safe restart function can also operate independently from the invention described above. For example, a wireless version of the invention can have separate plug-in modules for tools connected to the primary output of the invention and for devices connected to the secondary output (e.g. VAC). The safe restart function in either module functions separately from the invention to shut down the primary (TOOL) and/or secondary (VAC) outputs when connected devices are left “ON”.

Referring now toFIG.26, an operational flowchart for the invention is shown proceeding from when the device is “powered on” to when the VAC/accessory is shut down after a delay. Referring now toFIG.27, a schematic overview of a preferred embodiment of the invention is shown.

The circuits described above allow for a number of embodiments of the invention. Referring now toFIGS.30A,30B and30C, a plug-in stand-alone embodiment with two accessory outlets is shown.FIG.31shows an exemplary use of the embodiment inFIGS.30A-30C.

Referring now toFIG.32, an alternative embodiment using a “piggy back” plug is shown. InFIG.32, the switch circuit described above is located in the VAC1000and terminates in the “piggy back” plug700. The main device1010plugs into the plug700which is inserted into the main AC power supply. The circuitry in VAC1000then controls both the VAC1000and the main device1010as described above.FIG.33shows a preferred embodiment of the plug700.

Referring now toFIG.34, another alternative embodiment is shown where the switch described above is attached to an external power cord sheath800on the VAC/accessory device1000. The invention is contained in the sheath800on the power cord for the accessory device1000. The main device1010is then plugged into the sheath800and controlled thereby. Currents in the power cord of the VAC1000are preferably read by Hall effect sensors in the sheath800. Alternately, an embodiment can be configured such that the sheath800can be placed on the power cord of the main device1010and the accessory1000can be plugged into the sheath800in turn as shown inFIG.35.

Referring now toFIG.36, a preferred embodiment of a corded stand-alone version900of the invention is shown. The device900is plugged into the AC power supply (not shown) and the accessory1000and main device1010are plugged into the device900housing the circuitry described above to control both devices in turn.

Referring now toFIG.37, another alternative embodiment is shown where the circuit described above is housed in a safety switch950mounted on the main device1010. The main device1010is plugged into the switch950and the accessory/VAC1000is plugged into the switch950.

Thus, a variable control switch is described above. In each of the above embodiments, the different positions and structures of the present invention are described separately in each of the embodiments. However, it is the full intention of the inventor of the present invention that the separate aspects of each embodiment described herein may be combined with the other embodiments described herein. Those skilled in the art will appreciate that adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.

Various modifications and alterations of the invention will become apparent to those skilled in the art without departing from the spirit and scope of the invention, which is defined by the accompanying claims. It should be noted that steps recited in any method claims below do not necessarily need to be performed in the order that they are recited. Those of ordinary skill in the art will recognize variations in performing the steps from the order in which they are recited. In addition, the lack of mention or discussion of a feature, step, or component provides the basis for claims where the absent feature or component is excluded by way of a proviso or similar claim language.

As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives may be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.