Alternating polarity of attachment power terminals

Abstract

A device and powered attachment are disclosed. The device has two electrical terminals via which the powered attachment is configured to connect with the device and receive power from the device. The device has a terminal polarity switching circuit configured to switch a polarity of a voltage provided at the two electrical terminals. The powered attachment includes a first circuit and a second circuit that are connected in parallel with one another between the two electrical terminals when the powered attachment is connected with the device. The first circuit is configured to provide a first function when the voltage provided across the two electrical terminals has a first polarity. The second circuit is configured to provide a second function when the voltage provided across the two electrical terminals has an opposite second polarity.

Description

ALTERNATING POLARITY OF ATTACHMENT POWER TERMINALS

[0001] This application claims the benefit of priority of U.S. provisional application serial no. 62 / 627,361, filed on January 31, 2024 the disclosure of which is herein incorporated by reference in its entirety.FIELD

[0002] The device and method disclosed in this document relate to power tools and, more particularly, to alternating polarity of power tool attachment power terminals.BACKGROUND

[0003] Unless otherwise indicated herein, the materials described in this section are not admitted to be the prior art by inclusion in this section.

[0004] Power tools are often designed to work with a wide range of powered attachments, allowing them to perform different tasks by simply swapping out accessories. The power tool not only must provide power to the powered attachment but also needs a way to recognize which specific attachment is being used. Recognizing what specific attachment has been attached is necessary because different powered attachments have different power requirements or features, and the power tool needs to adjust its operation accordingly to operate the powered attachment.

[0005] Typically, the connection mechanism between the power tool and the powered attachments is somewhat complex. These connection mechanisms usually include at least two terminals to provide power, as well as one or more additional terminals needed toidentify the powered attachment or to provide some other secondary purpose. Such connection mechanisms add complexity to both the power tool and the powered attachment, increasing their manufacturing costs and making them bulkier.

[0006] What is needed is an attachment connection mechanism for both providing power to and identifying the powered attachment, while minimizing the complexity and cost of the power tool and the powered attachment.SUMMARY

[0007] A system is disclosed herein. The system comprises a device. The device includes (i) two electrical terminals. The device further includes (ii) a power source operably connected to provide a voltage across the two electrical terminals. The device further includes (ii) a terminal polarity switching circuit configured to switch a polarity of the voltage provided at the two electrical terminals. The system further comprises a powered attachment configured to connect with the device via the two electrical terminals and receive power from the device. The powered attachment includes (i) a first circuit to provide a first function when the voltage provided across the two electrical terminals has a first polarity. The powered attachment further includes (ii) a second circuit configured to provide a second function when the voltage provided across the two electrical terminals has a second polarity that is opposite the first polarity.

[0008] In some embodiments, the device is a power tool.

[0009] In some embodiments, the terminal polarity switching circuit is an H-bridge circuit.

[0010] In some embodiments, the terminal polarity switching circuit includes a double pole double throw switch.

[0011] In some embodiments, the first circuit and the second circuit are connected in parallel with one another between the two electrical terminals when the powered attachment is connected with the device.

[0012] In some embodiments, at least one of the first circuit and the second circuit includes a diode arranged to allow current to flow through the at least one of the first circuit and the second circuit only in one direction.

[0013] In some embodiments, the first function is providing illumination and the first circuit of the powered attachment is an LED illumination circuit.

[0014] In some embodiments, the powered attachment has a user interface and is configured to adjust a brightness of the illumination depending on a state of the user interface.

[0015] In some embodiments, the second function is identifying a type of the powered attachment, and the second circuit of the powered attachment includes at least one resistor having a resistance that uniquely corresponds to the type of the powered attachment.

[0016] In some embodiments, the device has a controller. The controller is configured to operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the second polarity. The controller is further configured to identify the type of the powered attachment by measuring the resistance of the second circuit while the voltage across the two electrical terminals has the second polarity.

[0017] In some embodiments, the powered attachment includes a user interface; the second function is communicating a state of the user interface to the device. The secondcircuit of the powered attachment includes an arrangement of a plurality of resistors and at least one switch configured such that a resistance of the second circuit is changeable by opening and closing the at least one switch. The at least one switch is opened and closed depending on the state of the user interface to change the resistance of the second circuit.

[0018] In some embodiments, the second circuit includes a diode connected in series with a first resistor of the plurality of resistors.

[0019] In some embodiments, the second circuit includes a first switch of the at least one switch connected in series with a second resistor of the plurality of resistors. The second resistor and the first switch are collectively in parallel with the first resistor.

[0020] In some embodiments, the second circuit includes a first switch of the at least one switch connected in parallel with a second resistor of the plurality of resistors. The second resistor and the first switch are collectively in series with the first resistor.

[0021] In some embodiments, the controller is configured to operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the second polarity. The controller is further configured to determine the state of the user interface of the powered attachment by measuring the resistance of the second circuit while the voltage across the two electrical terminals has the second polarity.

[0022] In some embodiments, the controller is further configured to alternatingly (i) operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the first polarity and (ii) operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the second polarity.

[0023] In some embodiments, the device has an actuator and is configured to operate the actuator depending on the state of the user interface of the powered attachment.

[0024] In some embodiments, the actuator is a motor and the controller is configured to adjust a speed of the motor depending on the state of the user interface of the powered attachment.

[0025] A device is also disclosed herein. The device comprises two electrical terminals configured to connect with a powered attachment. The device further comprises a power source operably connected to provide a voltage across the two electrical terminals. The device further comprises a terminal polarity switching circuit configured to switch a polarity of the voltage provided at the two electrical terminals. The device further comprises a controller. The controller is configured to operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with a first polarity to enable a first function of the powered attachment. The controller is further configured to operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with a second polarity to enable a second function of the powered attachment.

[0026] A powered attachment for connection to a device having two electrical terminals is also disclosed herein. The powered attachment comprises a first circuit configured to receive power from the device and to provide a first function when a voltage provided across the two electrical terminals has a first polarity. The powered attachment comprises a second circuit configured to receive power from the device and to provide a second function when the voltage provided across the two electrical terminals has a second polarity that is opposite the first polarity.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The foregoing aspects and other features of the system are explained in the following description, taken in connection with the accompanying drawings.

[0028] FIG. 1 shows a power tool system comprising a power tool and a powered attachment.

[0029] FIG. 2 shows a first exemplary embodiment of the terminal polarity switching circuit in the form of an H-bridge circuit.

[0030] FIG. 3 shows a second exemplary embodiment of the terminal polarity switching circuit in the form of a mechanical switching circuit.

[0031] FIG. 4 shows an exemplary primary function circuit in the form of a LED illumination circuit.

[0032] FIG. 5 shows an exemplary secondary function circuit in the form of an identification / code resistor circuit.

[0033] FIGs. 6A-6C show alternative configurations for identification / code resistor circuits.

[0034] FIG. 7 shows a circuit diagram of one exemplary power tool system, which is one embodiment of the power tool system of FIG. 1.DETAILED DESCRIPTION

[0035] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the presentdisclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the disclosure as would normally occur to one skilled in the art to which this disclosure pertains.

[0036] FIG. 1 shows a power tool system 100 comprising a power tool 110 and a powered attachment 140. The powered attachment 140 is configured to connect to the power tool 110 via a connection mechanism and to receive power from a power source 114 of the power tool 110. The connection mechanism between the power tool 110 and the powered attachment 140 is advantageously designed with only two electrical terminals, distinguished by the labels A and B in the figures. The electrical terminals A and B not only provide power from the power source 114 to the powered attachment 140 for a primary function, such as illumination, but also enable at least one secondary function, such as identifying the powered attachment 140 or enabling communication between the power tool 110 and the powered attachment 140.

[0037] To enable multiple functions, the power source 114 is connectable to the electrical terminals A and B with different polarities. In particular, when the power source 114 is connected to the electrical terminals A and B with a first polarity, a primary function of the powered attachment 140 is enabled. Conversely, when the power source 114 is connected to the electrical terminals A and B with an opposite second polarity, a secondary function of the powered attachment 140 is enabled. To these ends, the power tool 110 has a terminal polarity switching circuit 118 that is configured to switch a polarity of a connection between the power source 114 and the electrical terminals A and B. Particularly, in the first polarity, a positive terminal of the power source 114 is connected to terminal A and a negative terminal of the power source 114 is connected to terminal B,such that a positive voltage is provided from terminal A to terminal B. Conversely, in the second polarity, a positive terminal of the power source 114 is connected to terminal B and a negative terminal of the power source 114 is connected to terminal A, such that a positive voltage is provided from terminal B to terminal A.

[0038] The power tool 110 includes a controller 122, e.g., a microcontroller, that is configured to operate the terminal polarity switching circuit 118 to switch between the first polarity and the second polarity as necessary. In some embodiments, the controller 122 is also configured to operate tool actuators 126, e.g., a motor, to provide power tool features of the power tool 110. To these ends, in some embodiments, the power tool 110 includes a user interface 130, e.g., having buttons, triggers, or toggle switches arranged on a housing of the power tool 110, and the controller 122 is configured to operate the tool actuators 126 depending on the state of the user interface 130, e.g., the state of the buttons, triggers, or toggle switches.

[0039] The powered attachment 140 includes a primary function circuit 144 that implements the primary function of the powered attachment 140. When the powered attachment 140 is connected with the power tool 110, the primary function circuit 144 is connected between the terminals A and B. When the power source 114 is connected to the terminals A and B with the first polarity, a primary function circuit 144 receives power from the power source 114 and provides the primary function. To these ends, the primary function circuit 144 may include a diode that allows current to flow through the primary function circuit 144 only in one direction (i.e., corresponding to the first polarity). The primary function that is provided by the primary function circuit 144 may include anyfeature of the powered attachment that requires electrical power, such as providing illumination using a light source, or vacuuming or blowing using an electric fan.

[0040] The powered attachment 140 also includes a secondary function circuit that implements the secondary function of the powered attachment 140. The secondary function circuit 148 is connected in parallel with the primary function circuit 144 and, when the powered attachment 140 is connected with the power tool 110, is connected between the terminals A and B. When the power source 114 is connected to the electrical terminals A and B with the second polarity, a secondary function circuit 144 receives power from the power source 114 and provides the secondary function. To these ends, the secondary function circuit 148 may include a diode that allows current to flow through the secondary function circuit 148 only in one direction (i.e., corresponding to the second polarity). In at least some embodiments, the secondary function that is provided by the secondary function circuit 148 includes communicating information from the powered attachment 140. For example, in some embodiments, the secondary function circuit 148 includes a identification resistance that identifies the powered attachment. In some embodiments, the powered attachment 140 includes a user interface 152, e.g., having buttons, triggers, or toggle switches arranged on a housing of the powered attachment 140, and the secondary function circuit 148 adjusts the code resistance to indicate the current state of the user interface 152, e.g., the current state of the buttons, triggers, or toggle switches.

[0041] However, the secondary function that is provided by the secondary function circuit 148 may alternatively include any feature of the powered attachment that requires electrical power, such as providing illumination using a light source, or vacuuming or blowing using an electric fan. Moreover, it should be appreciated that the designation ofprimary and secondary functions does not necessarily indicate a relative importance in the design. As such any discussion of the primary function circuit 144 can be alternatively applied to the secondary function circuit 148 and, likewise, any discussion of the secondary function circuit 148 can be alternatively applied to the primary function circuit 144.

[0042] In one exemplary embodiment, the power tool 110 is a rotary power tool, such as those designed by Dremel™, that is compatible with a variety of interchangeable attachments and accessories that are designed for a wide range of tasks, including sanding, grinding, carving, polishing, and drilling. Such attachments are generally attached directly to an output shaft of the rotary power tool or secured to the output shaft using a collet or chuck system. Attachments typically perform their functions by mechanical rotation by the output shaft of the rotary power tool. However, unlike many attachments, the powered attachment 140 also provides multiple electrical functions, such as illumination, blowing, attachment identification, and communication of information to the rotary power tool. To provide such electrical functions, the powered attachment 140 must not only be mechanically engaged with the output shaft of the rotary power tool but also be electrically connected to receive electrical power from the power source 114 of the rotary power tool.

[0043] However, it should be appreciated, that the power tool 110 may comprise any power tool that interfaces with a powered attachment 140, peripheral, or accessory. Likewise, it should also be appreciated that, in some embodiments, the power tool system 100 may include, rather than the power tool 110, any other device that interfaces with a powered attachment 140, peripheral, or accessory. Any such device can incorporate the connection mechanism described herein to enable multiple electrical functions within the powered attachment 140 while only using two power terminals (A and B), thereby reducingthe cost and complexity of incorporating additional terminals and wires within the powered atachment 140 as well as in the device.Terminal Polarity Switching Circuit

[0044] As discussed above, the terminal polarity switching circuit 118 is configured to switch a polarity of a voltage provided at the two electrical terminals. To these ends, the terminal polarity switching circuit 118 comprises one or more switches that are operated by the controller 122 to switch a polarity of a connection between the power source 114 and the electrical terminals A and B. The controller 122 operates the switches of the terminal polarity switching circuit 118 in a first state to connect the voltage of the power source 114 across the terminals A and B with the first polarity to enable the first function of the powered attachment 140. Conversely, the controller 122 operates the switches of the terminal polarity switching circuit 118 in a second state to connect the voltage of the power source 114 across the terminals A and B with the second polarity to enable the second function of the powered attachment 140.

[0045] FIG. 2 shows a first exemplary embodiment of the terminal polarity switching circuit 118 in the form of an H-bridge circuit 200. As can be seen, the H-bridge circuit 200 includes four electronic switches, such as BJTs or MOSFETs, that are arranged in H-bridge circuit configuration. In the illustration, four electronic switches 230A, 230B, 230C, and 230D make up the H-bridge circuit configuration. In the illustrated embodiment, each of the electronic switches 230A, 230B, 230C, and 230D includes an integrated body diode or discrete flyback diode. In a first circuit branch 240, the electronic switches 230C and 230A are connected in series between a positive terminal 210 and a negative terminal 220 of thepower source 114. Likewise, in a second circuit branch 250, which is parallel with the first circuit branch 240, the electronic switches 230D and 23 OB are also connected in series between a positive terminal 210 and a negative terminal 220 of the power source 114. The terminal A is connected between the electronic switches 230C and 230A and the terminal B is connected between the electronic switches 230D and 23 OB.

[0046] The controller 122 operates the electronic switches 230A, 230B, 230C, and 230D to control a polarity of the voltage across the terminals A and B. Particularly, to apply voltage across the terminals A and B with a first polarity, the controller 122 operates the switches 230C and 230B to close and operates the switches 230D and 230A to open. Conversely, to apply voltage across the terminals A and B with an opposite second polarity, the controller 122 operates the switches 230C and 230B to open and operates the switches 230D and 230A to close.

[0047] FIG. 3 shows a second exemplary embodiment of the terminal polarity switching circuit 118 in the form of a mechanical switching circuit 300. As can be seen, the mechanical switching circuit 300 includes a double pole double throw switch 310, which is electrically operated. An equivalent configuration of multiple electrically operable mechanical switches (e.g., relays, contactors, etc.) can also be provided. The controller 122 operates the double pole double throw switch 310 in a first switching state to connect the power source 114 between the terminals A and B with a first polarity. Conversely, the controller 122 operates the double pole double throw switch 310 in a second switching state to connect the power source 114 between the terminals A and B with a second polarity.Exemplary Primary Function Circuitry of the Powered Atachment

[0048] As discussed above, the powered atachment 140 includes the primary function circuit 144 that receives power from the power tool 110 and provides a primary function when the voltage provided across the electrical terminals A and B has a first polarity. In some embodiments, the primary function of the powered atachment 140, which is enabled by the primary function circuit 144, is an illumination function. For example, the powered atachment 140 may include light-emitting diodes (LEDs) that are suitably arranged to illuminate a workspace around the powered attachment 140 and / or around the power tool 110. However, it should be noted that the primary function is not limited to illumination but may be extended to other functions. For example, the primary function circuit 144 may comprise a fan circuit configured to operate a fan to blow or provide suction. In another example, the primary function circuit 144 may comprise an identification / code resistor circuit configured for identifying a type of the powered atachment 140 or for communicating a state of the user interface 152 of the powered attachment 140 to the power tool 110.

[0049] FIG. 4 shows an exemplary primary function circuit 144 in the form of a LED illumination circuit 400. The LED illumination circuit 400 includes one or more LEDs 410 that are suitably connected such that, when voltage is provided across the terminals A and B with a first polarity, the LEDs 410 are illuminated. Conversely, when voltage is provided across the terminals A and B with an opposite second polarity, the LEDs 410 are illuminated. It should be appreciated that a wide variety of possible circuit arrangements exist that achieve this functionality.

[0050] In the illustrated exemplary embodiment, the LED illumination circuit 400 includes a first circuit branch 420 that is connected between the terminals A and B. The LEDs 410 are connected in series and / or parallel with one another within the first circuit branch 420. In the illustrated example, a first series-connected pair of LEDs 410 is connected in parallel with a second series-connected pair of LEDs 410. The arrangement of LEDs 410 is connected in series with a transistor 440 (e.g., an NPN transistor) and a resistor 450. The arrangement of LEDs 410 is connected between the terminal A and the transistor 440, whereas the resistor 450 is connected between the terminal B and the transistor 440. In one embodiment, the collector of the transistor 440 is connected to the arrangement of LEDs 410, and the emitter of the transistor 440 is connected to the resistor 450.

[0051] The LED illumination circuit 400 further includes a second circuit branch 430 that is connected between the terminals A and B. The second circuit branch 430 includes a transistor 460 connected in series with a resistor 470. The resistor 470 is connected between the terminal A and the transistor 460, whereas the transistor 460 is connected between the terminal B and the resistor 470. In one embodiment, the collector of the transistor 460 is connected to the resistor 470 and the emitter of the transistor 460 is connected to the terminal B. Finally, the base of the transistor 440 is connected between the transistor 460 and the resistor 470, whereas the base of the transistor 460 is connected between the transistor 440 and the resistor 450Secondary Function Circuitry of the Powered Atachment

[0052] As discussed above, the powered atachment 140 includes the secondary function circuit 148 that receives power from the power tool 110 and provides a secondary function when the voltage provided across the electrical terminals A and B has an opposite second polarity. In some embodiments, the secondary function of the powered atachment 140, which is enabled by the secondary function circuit 148, is communicating information about the powered atachment 140 to the power tool 110. More particularly, in at least some embodiments, the secondary function includes indicating and identifying a type of the powered atachment 140. In further embodiments, the secondary function includes communicating a state of the user interface 152 of the powered attachment 140 to the power tool 110. However, it should be noted that the secondary function is not limited to communicating information but may be extended to other functions. For example, the secondary function circuit 148 may comprise an illumination circuit configured to provide illumination. In another example, the secondary function circuit 148 may comprise a fan circuit configured to operate a fan to blow or provide suction.

[0053] For the purpose of indicating and identifying a type of the powered atachment 140, the secondary function circuit 148 includes at least one resistor, which may be referred to as an identification resistor, having a resistance that uniquely corresponds to the type of the powered attachment 140. The controller 122 operates the terminal polarity switching circuit 118 to provide the voltage across the terminals A and B with the second polarity. The controller 122 then identifies the type of the powered atachment 140 by measuring the resistance of the secondary function circuit 148 while the voltage across the terminalsA and B has the second polarity.

[0054] In a similar manner, for the purpose of communicating a state of the user interface 152 of the powered attachment 140 to the power tool 110, the secondary function circuit 148 includes an arrangement of switches and resistors, which may be referred to as code resistors, configured such that a resistance of the secondary function circuit 148 is changeable by opening and closing the switches. The switches are opened and closed depending on the state of the user interface 152 to change the resistance of the secondary function circuit 148. In particular, the switches of the secondary function circuit 148 may include manually operable buttons, triggers, or toggle switches of the user interface 152. Each combination of open and closed switches results in a different unique resistance of the secondary function circuit 148. The controller 122 operates the terminal polarity switching circuit 118 to provide the voltage across the terminals A and B with the second polarity. The controller 122 then determines the state of the user interface 152 (i.e., the particular combination of open / closed switches) by measuring the resistance of the secondary function circuit 148 while the voltage across the terminals A and B has the second polarity. In one embodiment, the controller 122 stores a look-up table that defines a correspondence between the state of the user interface 152 and the measured resistance of the secondary function circuit 148.

[0055] FIG. 5 shows an exemplary secondary function circuit 148 in the form of an identification / code resistor circuit 500. The identification / code resistor circuit 500 includes a diode 510 arranged in series with an identification resistor 520 between the terminals A and B. The diode 510 is oriented so as to allow current to flow through the identification / code resistor circuit 500 while the voltage provided across the terminals A and B has the second polarity, but block current from flowing through theidentification / code resistor circuit 500 while the voltage provided across the terminals A and B has the first polarity. The identification resistor 520 has a resistance that uniquely identifies the type of the powered attachment 140.

[0056] A first code resistor 530 and a first switch 540 are connected in series with one another and collectively in parallel with the identification resistor 520. The first switch 540 is configured to close when a first button, trigger, or toggle switch of the user interface 152 has been manually operated by the user. When the first switch 540 is closed, the total resistance of the identification / code resistor circuit 500 is reduced compared to the resistance of only the identification resistor 520. Similarly, a second code resistor 550 and a second switch 560 are connected in series with one another and collectively in parallel with the identification resistor 520. The second switch 560 is configured to close or open when a second button, trigger, or toggle switch of the user interface 152 has been manually operated by the user. When the second switch 560 is closed, the total resistance of the identification / code resistor circuit 500 is reduced compared to the resistance of only the identification resistor 520. The resistance of the second code resistor 550 is different from that of the first code resistor 530, such that each combination of closed / open states of the first switch 540 and the second switch 560 results in a different total resistance of the identification / code resistor circuit 500. It should be appreciated that the identification / code resistor circuit 500 may include any number of further branches having additional code resistors and additional switches.

[0057] FIGs. 6A-6C show alternative configurations for identification / code resistor circuits 600A-C. As shown in FIG. 6A, the identification / code resistor circuit 600A includes a diode 610 arranged in series with an identification resistor 620 and a first coderesistor 630 between the terminals A and B. The diode 610 is connected between the terminal A and the first code resistor 630. The identification resistor 620 is connected between the terminal B and the first code resistor 630. The diode 610 is oriented so as to allow current to flow through the identification / code resistor circuit 600A while the voltage provided across the terminals A and B has the second polarity, but block current from flowing through the identification / code resistor circuit 600A while the voltage provided across the terminals A and B has the first polarity. The identification resistor 620 (or the identification resistor 620 in combination with the first code resistor 630) has a resistance that uniquely identifies the type of the powered attachment 140.

[0058] A first switch 640 is connected in parallel with the first code resistor 630. Thus, the parallel connected first switch 640 and first code resistor 630 are collectively in series with the identification resistor 620. The first switch 640 is configured to close or open when a first button, trigger, or toggle switch of the user interface 152 has been manually operated by the user. When the first switch 640 is closed, the total resistance of the identification / code resistor circuit 600A is reduced compared to the resistance when the first switch 640 is open. It should be appreciated that the identification / code resistor circuit 600A may include any number of further branches having additional code resistors and additional switches.

[0059] As shown in FIG. 6B, the identification / code resistor circuit 600B is similar to the identification / code resistor circuit 600A. However, in addition to the already described components of the identification / code resistor circuit 600A, the identification / code resistor circuit 600B further includes a second code resistor 650 and a second switch 660, which are connected in series with one another and collectively in parallel with the identificationresistor 620. The second switch 660 is configured to close or open when a second button, trigger, or toggle switch of the user interface 152 has been manually operated by the user. When the second switch 660 is closed, the total resistance of the identification / code resistor circuit 600B is reduced compared to the resistance when the second switch 660 is open. It should be appreciated that the identification / code resistor circuit 600B may include any number of further branches having additional code resistors and additional switches.

[0060] As shown in FIG. 6C, the identification / code resistor circuit 600C is similar to the identification / code resistor circuit 600A. However, in addition to the already described components of the identification / code resistor circuit 600A, the identification / code resistor circuit 600C further includes a second code resistor 670 and a second switch 680, which are connected in series with one another and collectively in parallel with the series connection of the identification resistor 620 and the first code resistor 630. The second switch 680 is configured to close or open when a second button, trigger, or toggle switch of the user interface 152 has been manually operated by the user. When the second switch 680 is closed, the total resistance of the identification / code resistor circuit 600C is reduced compared to the resistance when the second switch 680 is open. It should be appreciated that the identification / code resistor circuit 600 A may include any number of further branches having additional code resistors and additional switches.Exemplary System

[0061] FIG. 7 shows a circuit diagram of one exemplary power tool system 700, which is one embodiment of the power tool system 100 of FIG. 1. In the illustrated exemplary embodiment, the terminal polarity switching circuit 118 of the power tool 110 takes theform of the H-bridge circuit 200, as described in greater detail with respect to FIG. 2. In the illustrated exemplary embodiment, the powered attachment 140 comprises the LED illumination circuit 400, as described in greater detail with respect to FIG. 4, and the identification / code resistor circuit 500, as described in greater detail with respect to of FIG. 5. The LED illumination circuit 400 and the identification / code resistor circuit 500 are connected in parallel between the terminals A and B. When voltage is applied across the terminals A and B with the first polarity, the LED illumination circuit 400 provides LED illumination. Conversely, when voltage is applied across the terminals A and B with the opposite second polarity, the identification / code resistor circuit 500 enables identification of the powered attachment 140 or communication of a state of the user interface 152 of the powered attachment 140 to the power tool 110.

[0062] For the purpose of measuring a resistance across the terminals A and B, the power tool system 700 includes at least one measurement circuit 710, 720. The controller 122 is operably connected to the at least one measurement circuit 710, 720 via respective measurement node 712, 722 thereof. Depending on the measurement configuration, in some embodiments, both of the measurement circuits 710 and 720 are provided and utilized such that the resistance across the terminals A and B can be measured in both the first and second polarities. In alternative embodiments, only one or the other of the measurement circuits 710, 720 is provided and utilized for measuring a resistance across the terminals A and B.

[0063] The measurement circuit 710 comprises a series connection of three resistors 714, 716, and 718 connected between the rail (i.e., the positive terminal of the power source 114) and ground. The measurement node 712 is arranged between the resistor 716 and theresistor 718. The terminal A is connected between the resistor 714 and the resistor 716. InThus, the code resistance is connected to a high side of the at least one measurement circuit 710. In some measurement configurations, the controller 122 measures a resistance across the terminals A and B based on a voltage at the measurement node 712.

[0064] The measurement circuit 720 comprises a series connection of three resistors 724, 726, and 728 connected between the voltage rail (i.e., the positive terminal of the power source 114) and ground. The measurement node 722 is arranged between the resistor 726 and the resistor 728. The terminal B is also connected between the resistor 726 and the resistor 728. Thus, the code resistance is connected to a low side of the at least one measurement circuit 720. In some measurement configurations, the controller 122 measures a resistance across the terminals A and B based on a voltage at the measurement node 722.Operation of the Powered Attachment

[0065] The controller 122 is configured to operate the terminal polarity switching circuit 118 to switch between the first polarity and the second polarity as necessary. Particularly, the controller 122 operates the terminal polarity switching circuit 118 to provide the voltage across the terminals A and B with the first polarity. Likewise, the controller 122 operates the terminal polarity switching circuit 118 to provide the voltage across the terminals A and B with the second polarity.

[0066] In some embodiments, the user interface 130 of the power tool 110 includes a button, trigger, or toggle switch that can be manipulated by the user to manually select the primary function or the secondary function of the powered attachment 140. To this end,the controller 122 operates the terminal polarity switching circuit 118 to switch between the first polarity and the second polarity depending on the user’s interactions with the user interface 130.

[0067] In some embodiments, the controller 122 may be configured to change the polarity of the terminals A and B at predetermined intervals. Particularly, in one embodiment, the controller 122 detects attachment of the powered attachment 140 to the power tool 110. In response to detecting the powered attachment 140, the controller 122 operates the terminal polarity switching circuit 118 to provide the voltage across the terminals A and B with the second polarity. The controller 122 then identifies the type of the powered attachment 140 by measuring the resistance of the secondary function circuit 148 while the voltage across the terminals A and B has the second polarity, as discussed above. In one embodiment, depending on the determined type of the powered attachment 140, the controller 122 is configured to adjust the operation of the tool actuators 126. In one embodiment, depending on the determined type of the powered attachment 140, the controller 122 is configured to adjust the voltage provided across the terminals A and B in the first polarity (e.g., increase or decrease the voltage as suitable for the type of powered attachment 140).

[0068] In some embodiments, controller 122 is configured to operate the terminal polarity switching circuit 118 to switch between the first polarity and the second polarity in an alternating fashion at a predetermined frequency and a predetermined duty cycle. The resistance of the secondary function circuit 148 (e.g., the code resistor circuit 500) can thus be measured periodically. This periodicity is designed such that it has a minimal impact on the primary function. For example, the time period needed to measure the resistance of thesecondary function circuit 148 should not produce any noticeable flicker, or perceived reduction in brightness, in the LED illumination of the primary function circuit 144.

[0069] To these ends, the controller 122 alternatingly (i) operates the terminal polarity switching circuit 118 to provide the voltage across the terminals A and B with the first polarity and (ii) operates the terminal polarity switching circuit 118 to provide the voltage across the terminals A and B with the second polarity. While the voltage across the terminals A and B has the first polarity, the primary function of the powered attachment 140 is enabled (e.g., LED illumination). However, while the voltage across the terminals A and B has the second polarity, the controller 122 determines the state of the user interface 152 (i.e., the particular combination of open / closed switches) by measuring the resistance of the secondary function circuit 148, as discussed above. The predetermined frequency and the predetermined duty cycle are selected such that changes in the state of the user interface 152 of the powered attachment can be reliably and rapidly detected while minimizing interruption of the primary function, and such that the controller 122 has a minimum processing time required to measure the resistance and detect button presses. In one example, the predetermined duty cycle is, for example, 90% or higher in the first polarity to minimize flicker in the LED illumination and the predetermined frequency is, for example, at least 10 Hz to ensure detection of button presses.

[0070] Based on the determined state of the user interface 152, the controller 122 performs various operations. In this way, the power tool 110 can be indirectly operated using the user interface 152 of the powered attachment 140. In some embodiments, the controller 122 operates one or more of the tool actuators 126 in a particular manner depending on the state of the user interface 152 of the powered attachment 140. Forexample, in one embodiment, the controller 122 adjusts a speed of a motor of the power tool 110 depending on the state of the user interface 152 of the powered attachment 140. Thus, the user can control the speed of a motor of the power tool 110 by manipulating the user interface 152 of the powered attachment 140. In one embodiment, depending on the state of the user interface 152 of the powered attachment 140, the controller 122 is configured to adjust the voltage provided across the terminals A and B in the first polarity. In one example, the controller 122 increases or decreases the voltage applied in the first polarity to adjust an LED brightness or fan speed in the powered attachment 140. It should be appreciated that, in some embodiments, the powered attachment may also include circuitry for directly adjusting an LED brightness or fan speed in the powered attachment 140 based on the user interface 152, without requiring communication with the power tool 110. In another example, the controller 122 turns on or off the voltage applied in the first polarity to power on or power off the primary function of the powered attachment 140. It should be appreciated that, in some embodiments, the powered attachment may also include circuitry for directly turning on or turning off the powered attachment 140 based on the user interface 152, without requiring communication with the power tool 110.

[0071] While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same should be considered illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications, and further applications that come within the spirit of the disclosure are desired to be protected.

Claims

What is claimed is:

1. A system comprising: a device including (i) two electrical terminals, (ii) a power source operably connected to provide a voltage across the two electrical terminals, and (ii) a terminal polarity switching circuit configured to switch a polarity of the voltage provided at the two electrical terminals; and a powered attachment configured to connect with the device via the two electrical terminals and receive power from the device, the powered attachment including (i) a first circuit to provide a first function when the voltage provided across the two electrical terminals has a first polarity, and (ii) a second circuit configured to provide a second function when the voltage provided across the two electrical terminals has a second polarity that is opposite the first polarity.

2. The system according to claim 1, wherein the device is a power tool.

3. The system according to claim 1, wherein the terminal polarity switching circuit is an H-bridge circuit.

4. The system according to claim 1 , wherein the terminal polarity switching circuit includes a double pole double throw switch.

5. The system according to claim 1, wherein the first circuit and the second circuit are connected in parallel with one another between the two electrical terminals when the powered attachment is connected with the device.

6. The system according to claim 1 , wherein at least one of the first circuit and the second circuit includes a diode arranged to allow current to flow through the at least one of the first circuit and the second circuit only in one direction.

7. The system according to claim 1 , wherein the first function is providing illumination and the first circuit of the powered attachment is an LED illumination circuit.

8. The system according to claim 7, wherein the powered attachment has a user interface and is configured to adjust a brightness of the illumination depending on a state of the user interface.

9. The system according to claim 1 , wherein the second function is identifying a type of the powered attachment, and the second circuit of the powered attachment includes at least one resistor having a resistance that uniquely corresponds to the type of the powered attachment.

10. The system according to claim 9, wherein the device has a controller configured to: operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the second polarity; andidentify the type of the powered attachment by measuring the resistance of the second circuit while the voltage across the two electrical terminals has the second polarity.

11. The system according to claim 1, wherein: the powered attachment includes a user interface; the second function is communicating a state of the user interface to the device; and the second circuit of the powered attachment includes an arrangement of a plurality of resistors and at least one switch configured such that a resistance of the second circuit is changeable by opening and closing the at least one switch, the at least one switch being opened and closed depending on the state of the user interface to change the resistance of the second circuit.

12. The system according to claim 11, wherein the second circuit includes a diode connected in series with a first resistor of the plurality of resistors.

13. The system according to claim 12, wherein the second circuit includes a first switch of the at least one switch connected in series with a second resistor of the plurality of resistors, the second resistor and the first switch being collectively in parallel with the first resistor.

14. The system according to claim 12, wherein the second circuit includes a first switch of the at least one switch connected in parallel with a second resistor of the plurality of resistors, the second resistor and the first switch being collectively in series with the first resistor.

15. The system according to claim 11, wherein the device has a controller configured to: operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the second polarity; and determine the state of the user interface of the powered attachment by measuring the resistance of the second circuit while the voltage across the two electrical terminals has the second polarity.

16. The system according to claim 15, wherein the controller is configured to: alternatingly (i) operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the first polarity and (ii) operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with the second polarity.

17. The system according to claim 15, wherein the device has an actuator and is configured to operate the actuator depending on the state of the user interface of the powered attachment.

18. The system according to claim 17, wherein the actuator is a motor and the controller is configured to adjust a speed of the motor depending on the state of the user interface of the powered attachment.

19. A device comprising: two electrical terminals configured to connect with a powered attachment; a power source operably connected to provide a voltage across the two electrical terminals; and a terminal polarity switching circuit configured to switch a polarity of the voltage provided at the two electrical terminals; and a controller configured to: operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with a first polarity to enable a first function of the powered attachment; and operate the terminal polarity switching circuit to provide the voltage across the two electrical terminals with a second polarity to enable a second function of the powered attachment.

20. A powered attachment for connection to a device having two electrical terminals, the powered attachment comprising: a first circuit configured to receive power from the device and to provide a first function when a voltage provided across the two electrical terminals has a first polarity; anda second circuit configured to receive power from the device and to provide a second function when the voltage provided across the two electrical terminals has a second polarity that is opposite the first polarity.

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