TRIGGER APPARATUS FOR POWERED DEVICE, POWERED DEVICE, AND METHOD OF CONTROLLING AN OPERATION OF A POWERED DEVICE

Abstract

A trigger apparatus for a powered device, such as a power tool is disclosed. The powered device comprises a trigger operable by a user to move from a first position to at least one second position so as to control an operation of the powered device. The trigger apparatus comprises: a linear Hall effect sensor for measuring a change in a magnetic field associated with the trigger being moved from the first position to the at least one second position, and configured to generate a sensor signal based on the measured magnetic field, for controlling the operation of the powered device; a power module configured to power, the linear Hall effect sensor, upon reception of an activation signal for indicating that the trigger apparatus is to be activated; and an activation switch configured to generate the activation signal, when the trigger is moved from the first position. A powered device comprising the trigger apparatus and a method of controlling an operation of a powered device are also disclosed.

Claims

1. A trigger apparatus for a powered device, such as a power tool, the powered device comprising a trigger operable by a user to move from a first position to at least one second position so as to control an operation of the powered device, the trigger apparatus comprising: a linear Hall effect sensor for measuring a change in a magnetic field associated with the trigger being moved from the first position to the at least one second position, and configured to generate a sensor signal for controlling the operation of the powered device based on the change in the magnetic field; a power module configured to power, the linear Hall effect sensor, upon reception of an activation signal for indicating that the trigger apparatus is to be activated; and an activation switch configured to generate the activation signal, when the trigger is moved from the first position.

2. The trigger apparatus according to claim 1, wherein the activation switch is a microswitch.

3. The trigger apparatus according to claim 1 or claim 2 comprising the trigger, and wherein the trigger apparatus is configured such that a movement of the trigger from the first position to the at least one second position causes a change in the magnetic field measured by the linear Hall effect sensor.

4. The trigger apparatus according to any one of claim 1 to 3, comprising a magnetic element for generating a magnetic field.

5. The trigger apparatus according to claim 4, wherein the trigger apparatus is configured such that the trigger being moved from the first position to the second position causes a corresponding change to a positional relationship between the magnetic element and the linear Hall effect sensor by way of movement of the trigger.

6. The trigger apparatus according to any one of claim 1 to 5, wherein the trigger is operable by the user to reversibly move between the first position and the at least one second position, and wherein: the power module is configured to stop powering the linear Hall effect sensor upon reception of a deactivation signal for indicating that the trigger apparatus is to be deactivated; and the activation switch is configured to generate the deactivation signal when the trigger is moved to the first position.

7. The trigger apparatus according to any one of claim 1 to 6, further comprising a controller for receiving the sensor signal and for generating one or more control signals to control the operation of the powered device, wherein the power module is configured to power the controller upon reception of the activation signal.

8. The trigger apparatus according to claim 7, wherein the controller is configured to generate a second activation signal for causing the power module to continue to power the controller for a specific duration.

9. The trigger apparatus according to claim 7 or 8, when dependent upon claim 6, wherein the controller is configured to receive the deactivation signal from the activation switch and transmit a second deactivation signal to the power module; and the power module is configured to stop powering the controller upon reception of the second deactivation signal.

10. A powered device comprising the trigger apparatus of any one of claims 1 to 9, the powered device comprising: the trigger; an electric motor; and a power supply module for receiving power from a power source and configured to provide power to at least one of the power module of the trigger apparatus and the electric motor, wherein the powered device is configured to operate the electric motor based on the sensor signal.

11. The powered device according to claim 10, further comprising a drive circuit for driving the electric motor: wherein the trigger apparatus comprises a controller configured to generate one or more control signals to control the drive circuit, based on the sensor signal; and the activation switch is configured to disable at least one input of the drive circuit when the trigger is at the first position so as to interrupt an operation of the electric motor.

12. A method of controlling an operation of a powered device, preferably according to any of the preceding claims 10 and 11, the device comprising a trigger operable by a user to move from a first position to at least one second position so as to control the operation of the device, the method comprising: generating, using an activation switch, an activation signal when the trigger is moved from the first position; powering a linear Hall effect sensor upon generation of the activation signal; measuring, using the linear Hall effect sensor, a change in a magnetic field associated with the trigger being moved from the first position to the at least one second position; generating, a sensor signal for controlling the operation of the powered device based on the change in the magnetic field; and controlling the operation of the device based on the sensor signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] In the following, aspects of the present disclosure will be described by reference to the following Drawings, by way of example only, in which:

[0090] FIG. 1 shows a schematic view of a trigger apparatus for a powered device according to a first embodiment;

[0091] FIGS. 2A to 2C show the output of the microswitch and the sensor signal as a function of the position of the push button;

[0092] FIGS. 3A to 3C show a trigger apparatus for a powered device and the trigger;

[0093] FIG. 4 shows a schematic view of the trigger apparatus in an electric sander as a powered device;

[0094] FIG. 5 shows a schematic view of the logic gate, and parts of the motor drive and the BLDC motor;

[0095] FIGS. 6A to 6D show a schematic view of the push button, the microswitch and the linear Hall effect sensor at different time instants;

[0096] FIG. 6E shows the output of the microswitch and the sensor signal S at the different time instants;

[0097] FIG. 6F shows the speed of the BLDC motor at the different time instants; and

[0098] FIGS. 7A and 7B show a schematic view of a trigger, a linear Hall effect sensor and a coil, according to a second embodiment.

[0099] FIGS. 8A and 8B show schematic views of the logic gate, and parts of the motor drive and the BLDC motor according to a modification;

DETAILED DESCRIPTION OF EMBODIMENTS

First Embodiment

[0100] FIG. 1 shows a schematic view of a trigger apparatus 100 for a powered device. The power device comprises a push button 200 as a trigger, to be operated by the user to move between a first position P1 and at least one second position P2-1˜P2-n.

[0101] In the present embodiment, the first position P1 corresponds to an initial position against which the trigger is biased by a helical spring (not shown) when not operated by a user. In other words, the trigger is reversibly movable between the first position P1 and the at least one second position P2-1 P2-n.

[0102] The trigger 200 comprises a permanent magnet 210, for example a neodymium magnet, as a magnetic element, which generates a constant magnetic field.

[0103] A microswitch 110 is configured to cooperate with the trigger 200, such that the microswitch 110 is in an off state when the trigger 200 is at the first position P1, and the microswitch 110 switches to an on state when the trigger 200 is moved from the first position P1. More specifically, when the trigger 200 is moved from the first position P1, the electric terminals of the microswitch 110 are made to contact each other, and an activation signal A is generated from the microswitch 110.

[0104] The microswitch outputs a binary signal, and to generate the activation signal A, the output of the microswitch switches to a logical high and is maintained at a logical high until the trigger 200 is moved back to the first position P1, at which point the output of the microswitch switches back to a logical low.

[0105] A power module 120 receives the activation signal A. The power module 120 is electrically coupled to a Li-ion battery 310 providing a 10.8V DC power, for example. The power module 120 receives power from the battery 310 to selectively power a linear Hall effect sensor 130 and a controller 140, via a low-voltage power bus 150.

[0106] The power module 120 comprises a DC-DC converter (not shown) configured to transform the (exemplary) 10.8V power provided by the battery to a lower voltage required to power the linear Hall effect sensor 130 and the microcontroller 140, and a voltage regulator to maintain the voltage on the voltage bus 150. When the power module 120 receives the activation signal A, the power module 120 provides power to the linear Hall effect sensor 130 and the microcontroller 140 via the low-voltage power bus 150, until reception of a second deactivation signal from the microcontroller 140.

[0107] Upon being powered, the linear Hall effect sensor 130 measures a magnetic field in its vicinity. The linear Hall effect sensor 130 is oriented towards the trigger 200 and the permanent magnet 210 in the trigger 200.

[0108] When the trigger 200 is operated by the user to move from the first position P1 towards one of the second positions P2-1 P2-n, the permanent magnet 210 moves closer to the linear Hall effect sensor 130, which causes the density of the magnetic field measured by the linear Hall effect sensor 130 to increase as the trigger 200 is moved closer to the linear Hall effect sensor 130.

[0109] The linear Hall effect sensor 130 generates a sensor signal S based on the measured magnetic field and with an amplitude proportional to the density of the measured magnetic field.

[0110] The microcontroller 140 comprises a non-volatile memory (not-shown) for storing instructions, such as a ROM, EPROM, EEPROM or flash memory, a processing unit (not shown) for executing the instructions stored on the non-volatile memory, such as a CPU, and a RAM used by the processing unit when executing the instructions.

[0111] The microcontroller 140 receives the sensor signal S and detects a change in the measured magnetic field, by comparing the magnetic field measured by the linear Hall effect sensor 130 at two different time instants. When a change in the measured magnetic field is detected, this is associated with a movement of the trigger 200. The microcontroller 140 determines a presumed amount by which the trigger 200 was moved based on the amount of change detected in the magnetic field. The microcontroller 140 generates three control signals C1, C2 and C3 to control each phase of a three-phased electric motor, so as to operate the electric motor in accordance with the amount by which the trigger 200 is considered to have been moved by the user.

[0112] Although not shown on FIG. 1, the microcontroller 140 also receives the activation signal A from the microswitch 110 and can determine the state of the microswitch 110.

[0113] FIGS. 2A to 2C show the output of the microswitch signal A and the sensor signal S as a function of the position of the push button 200 relative to the linear Hall effect sensor 130. The push button 200 is configured to move along an axis X.

[0114] FIG. 2A shows the first position P1, the position P1′ in the near proximity of the first position where the microswitch 110 switches its state, and a plurality of second positions P2-1 to P2-n, which are consecutively nearer the linear Hall effect sensor 130.

[0115] As shown on FIG. 2B, the microswitch 110 does not switch when the trigger is moved from the first position P1 by an infinitesimal amount, but only once the trigger is moved to a position P1′ located in the near proximity of the first position P1, to avoid accidental activation of the device and due to the physical limitations of the microswitch.

[0116] The output of the microswitch 110 is at a logical low whilst the push button 200 is at the first position P1 or between the first position P1 and the position P1′ and switches to a logical high when the push button 200 is moved from the first position P1 past the position P1′. The output of the microswitch 110 continues to be a logical high until the trigger 200 is moved back to the first position P1 (or, at least back until position P1′).

[0117] As shown on FIG. 2C, when the push button 200 is at or near the first position P1, the sensor signal S is zero, or a negligibly low value. When the push button 200 is moved to near the second position P2-1, the amplitude of the sensor signal S starts to increases and continuously increases as the push button 200 is further moved along the axis X towards the linear Hall effect sensor 130. Accordingly, the amplitude of the sensor signal S is proportional to a movement of the trigger 200.

[0118] FIGS. 3A to 3C show a trigger apparatus 100 for a powered device and the trigger 200. FIGS. 3A and 3B show perspective views of the trigger apparatus 100 from different angles, and FIG. 3C shows a side view of the trigger apparatus 100.

[0119] FIG. 3A shows the push button 200 as the trigger being biased in the first position P1 by the helical spring 220. As the push button 220 is moved by the user, the helical spring 220 is compressed and an arm 230 of the push button 220 actuates the microswitch 110, which generates an activation signal S.

[0120] The magnet 210 is placed in the region which the linear Hall effect sensor 130 measures the magnetic field with the highest sensitivity, and the magnet 210 is moved along an axis intersecting the sensing surface of the linear Hall effect sensor 130. This allows the trigger apparatus 100 to accurately detect changes in the magnetic field generated by the magnet 210.

[0121] As shown on FIGS. 3B and 3C, the magnet 210 is placed within the helical spring 220, and thus does not require additional space on the trigger 200, thereby reducing the space requirements of the trigger 200.

[0122] FIG. 4 shows a schematic view of the trigger apparatus 100 in an electric sander 300 as a powered device.

[0123] The electric sander 300 comprises the battery 310, a power supply module 320, a logic circuit 330, a motor drive 340, and an electric motor 350.

[0124] The battery 310 supplies power to the power supply module 320, which in turns supplies power to the power module 120 and the motor drive 340.

[0125] The logic circuit 330 receives the activation signal A, which indicates the state of the microswitch 110, and the three control signals C1˜C3 from the microcontroller 140, and outputs signals to control the motor drive 340.

[0126] The logic circuit 330 performs a logical AND operation on the activation signal A and each of the control signals C1˜C3. That is, if the output of the microswitch 110 is a logical high, indicating that the trigger 200 is moved from the first position P1, the logic circuit 330 allows the control signals C1˜C3 to be transmitted to the motor drive 340.

[0127] Otherwise, the logic circuit 330 outputs logical low signals thereby interrupting the supply of power to the electric motor 350 and thus interrupting the motor operation.

[0128] The motor drive 340 receives the signals output by the logical circuit 340 and drives the electric motor 350 accordingly.

[0129] In the present embodiment, the motor drive 340 has a three-phased DC to AC converter in a half-bridge configuration to drive each of the phase windings of the electric motor 350 using the power supplied by the power supply module 320.

[0130] The electric motor 350 is a three-phased brushless DC (BLDC) motor having a rotor including permanent magnets and electrically commutated stator windings. The user can variably control the rotation speed of the BLDC motor 350 by controlling the movement of the trigger 200 from the first position P1 to one of the second positions P2-1˜P2-n.

[0131] The control signals C1˜C3 are generated using a pulse-width modulation to operate the BLDC motor at the speed determined by the user, using a pulse-width modulation and an indication of the current speed of the motor.

[0132] FIG. 5 shows a schematic view of the logic gate 330, and parts of the motor drive 340 and the BLDC motor 350.

[0133] The logic gate 330 comprises three logical AND gates 332, 334 and 336. The AND gates each receives the activation signal A from the microswitch 110 as one of the input, and a respective one of the control signals C1˜C3 from the controller 140 as the other input. Therefore, the output of AND gate 332 can only be a logical high if the activation signal is a logical high. Accordingly, the activation and deactivation signals from the microswitch can disable an input of the motor drive 340.

[0134] FIG. 5 also shows the part of the motor drive 340 used to control one phase of the BLDC motor 350. The motor drive 340 comprises a pair of IGBTs 342 and 344 which are connected in series to the DC voltage provided by the power supply module 320, indicated with the V+ and V− on FIG. 5. The output of the AND gate 332 is connected to the gate terminal of IGBT 342 and to an inverter 346. The output of the inverter 346 is connected to the gate terminal of IGBT 344, such that the IGBTs 342 and 344 are not simultaneously on.

[0135] The common node of IGBTs 342 and 344 is connected to the phase winding 352 of the BLDC motor 350. The control signal C1 is used to determine if an electric path is formed from terminal V+ to the phase winding 352 via IGBT 342 or an electric path is formed from terminal V− to the phase winding 352 via IGBT 344, and consequently to determine the magnetic field generated by the current in the phase winding 352.

[0136] Although FIG. 5 shows only one pair of IGBTs and one phase winding, it would be apparent to a person skilled in the art that the number of IGBT pairs in the motor drive 340 corresponds to the number of phase windings in the electric motor 350.

[0137] FIGS. 6A to 6D show a schematic view of the push button 200, the microswitch 110 and the linear Hall effect sensor 130 at different time instants t0, t1, t2 and t3 during an operation of the push button 200 by the user.

[0138] At time instant t=t0, shown on FIG. 6A, the push button 200 is moved from the first position P1.

[0139] At time instant t=t1, shown on FIG. 6B, the push button 200 is moved to the second position P2-1.

[0140] At time instant t=t2, shown on FIG. 6C, the push button 200 is moved to another second position P2-2.

[0141] At time instant t=t3, shown on FIG. 6D, the push button 200 is released by the user and moved back to the first position P1 by the coil spring 220 acting on the push button 200.

[0142] FIG. 6E show the output of the microswitch 110 (that is, the activation signal and the deactivation signal), and the sensor signal S at the time instants t0 to t3.

[0143] FIG. 6F show the speed of the BLDC motor 350 at the time instants t0 to t3.

[0144] At time instant t=t0, the microswitch 110 is actuated, and its output switches to a logical high, thereby generating the activation signal. At that time instant, the sensor signal S is at a negligibly low value, and the BLDC motor 350 is still.

[0145] At time instant t=t1, the sensor signal S increases to a value S1. As a result the microcontroller 140 controls the BLDC motor 350 to rotate at speed V1, which is achieved shortly after t1.

[0146] Between time instants t1 and t2, the push button 200 is moved from position P2-1 to P2-2. As a result, the amplitude of the sensor signal S increases continuously, to reach a second value S2, higher than S1. The microcontroller 140 receiving the sensor signal S increase the rotation speed of the BLDC motor 350 to a second speed V2 higher than speed V1.

[0147] At time instant t=t3, the output A of the microswitch switches to a logical low, thereby generating the deactivation signal.

[0148] The power module 120 receiving the deactivation signal interrupts the power being provided to the linear Hall effect sensor 130, which results in the amplitude of sensor signal S to drop rapidly to zero.

[0149] Upon receiving the deactivation signal, the microcontroller 140 generates a second activation signal to the power module 120 so that the microcontroller 140 is continued to be powered for a predetermined period of time after the push button 200 is moved back to the first position P1. During that period of time, the microcontroller 140 reduces the rotation speed of the BLDC motor 350 until complete stop whilst avoiding an unsafe sudden stop of the motor.

[0150] Then, the microcontroller 140 generates a second deactivation signal to the power module 120. The power module 120 receiving the second deactivation signal interrupts the power being provided to the microcontroller 140.

Second Embodiment

[0151] FIGS. 7A and 7B show a schematic view of a trigger 1200, a linear Hall effect sensor 1300 and a coil 1060 as a magnetic element, according to a second embodiment.

[0152] The coil 1060 is used to generate the magnetic field, instead of the permanent magnet 230. Additionally, the coil 1060 has a fixed positional relationship with the linear Hall effect sensor 1300, and is located near the linear Hall effect sensor 1300.

[0153] The coil 1060 is electrically coupled to an AC power source (not shown) selectively providing a constant amplitude AC current to the coil 1060 when the trigger 1200 is away from the first position P1.

[0154] The coil 1060 generates a periodic magnetic field, which can be measured by the linear Hall effect sensor 1300, to generate a sensor signal S having the same periodicity as the periodic magnetic field and an amplitude proportional to the density of the periodic magnetic field.

[0155] The trigger 1200 comprises a magnetic shielding element 1230 configured to move between the coil 1060 and the linear Hall effect sensor 1300 as the trigger 1200 is moved from the first position P1 (shown on FIG. 7A) to the second position(s) P2-1˜P2-n (shown on FIG. 7B).

[0156] The magnetic shielding element 1230, made for example of a mu-metal, is configured to increasingly attenuate the magnetic field density in the vicinity of the linear Hall effect sensor 1300 as the trigger is moved further away from the first position P1. Accordingly, the density of the periodic magnetic field generated by the coil in the vicinity of the linear Hall effect sensor 1300 is reduced as the trigger 1200 is moved further from the first position P1.

[0157] By comparing successive maximum in the periodic sensor signal, the microcontroller 140 can detect a change in the magnetic field, and determine a movement of the trigger associated with the change in the magnetic field.

[0158] [Modifications and Variations]

[0159] The permanent magnet 210 of the first embodiment may be replaced by the coil 1060 of the second embodiment or any other magnetic element. Similarly, the coil 1060 of the second embodiment may be replaced by a permanent magnet or any other magnetic element.

[0160] In the first embodiment, the permanent magnet 210 is in the trigger 200 and moves, relative to the linear Hall effect sensor 130, by movement of the trigger 200. Instead, the linear Hall effect sensor 130 may be in the trigger 200 such that it is moved, relative to the permanent magnet 210, by movement of the trigger 200.

[0161] In the second embodiment, the trigger 1200 comprises the magnetic shielding element 1230. Instead, the magnetic shielding element 1230 may be positioned between the coil 1060 and the linear Hall effect sensor 1300, and the trigger 1200 may be configured such that a movement of the trigger 1200 causes the magnetic shield to be moved away from the coil 1060 and the linear Hall effect sensor 1300, such that the maximum density of the magnetic field measured by the linear Hall effect sensor 1300 increases as the trigger 1200 is moved from the first position.

[0162] In the first embodiment, the output of the microswitch is described as being continuously at a logical high until the push button 200 is moved back to the first position. Instead, the actuation of the microswitch when the push button is moved past position P1′ may cause a short impulse generated by an impulse generator connected to the terminal of the microswitch 110, which is received by the power module 120, the microcontroller 140 and the logic gate 330. Similarly, moving the push button 200 back to the first position P1 may generate another short impulse which is received by the microcontroller 140, which would correspond to a predetermined event.

[0163] The power module 120 comprises a timer which is initiated by the reception of the activation signal A, and the power module 120 provides power to the linear Hall effect sensor and the microcontroller 140 until expiration of the timer. The microcontroller 140 periodically generates the second activation signal to reset the timer in the power module 120, such that the linear Hall effect sensor 130 and the microcontroller 140 are continuously powered. When the microcontroller 140 receives the short impulse corresponding to a deactivation signal, the microcontroller may stop generating the second activation signal so that the power module 120 interrupts the power being provided to the linear Hall effect sensor 130 and the microcontroller upon expiry of the timer. Alternatively, the power module 120 may receive the deactivation signal (an example of a predetermined event) directly and interrupt the power being provided to the microcontroller 140 and the linear Hall effect sensor 130.

[0164] The logic gate 330 comprise a logical buffer circuit, such as a J-K flip-flop, configured to change its output depending on the state of the inputs, and to use the activation signal and the deactivation signal as inputs to the buffer circuit.

[0165] Accordingly, even if the activation signal is a short impulse, the logic gate 330 may continue to allow the control signals to be provided to the motor drive 340 until the logic gate 330 receives a deactivation impulse signal, which resets the output of the buffer circuit.

[0166] In the First embodiment, the power source is described as a 10.8V battery providing DC power. However, the power source may also be an external AC power source, in which case the power supply module 320 comprises an AC to DC converter to provide DC power to the power module 120. The value of the voltage described to be provided by the battery in the embodiment (10.8 V) is merely illustrative and the battery may provide any other voltage. Similarly, the battery in the present disclosure is not limited to Li-ion batteries but may be of any other known type of batteries such as lead acid batteries, nickel metal hybrid or Zinc based batteries.

[0167] In the First embodiment, the magnet 210 is kept in the region in which the linear Hall effect sensor 130 measures the magnetic field with the highest sensitivity, and is moved along an axis towards or away from the linear Hall effect sensor 130. However, the push button 200 may alternatively be configured to move the magnet 210 from a position which is not in the region in which the linear Hall effect sensor 130 measures the magnetic field with the highest sensitivity, towards that region, thereby increasing the density of the magnetic field measured by the linear Hall effect sensor.

[0168] Alternatively, the push button 200 may be configured to change the orientation of the poles of the magnet 210 relative to the linear Hall effect sensor 130, for example by rotating the magnet 210 about itself, without changing the distance or the position of the magnet 210 relative to the linear Hall effect sensor 130.

[0169] In embodiments described above, the powered device is an electric sander comprising a BLDC motor 350. However, the electric sander may alternatively comprise another type of motor having a variably controllable speed, or the powered device may be another power tool having for example an actuator which controls an amount of output flow. In case the trigger apparatus 100 is used to control an actuator, the microcontroller 140 may generate a single control signal C1 for controlling the position of the actuator.

[0170] In embodiments described above, the movement of the trigger causes a corresponding movement of the magnetic element towards the linear Hall effect sensor 130. However, it would be apparent that the movement of the trigger may cause the magnetic element away from the linear Hall effect sensor 130.

[0171] In the present disclosure, the terms logical high and logical low are used to describe two distinct states of a binary signal. Conventionally, the logical high represents the state when an electrical conductor carrying the signal is at a relatively higher voltage than the logical low. However, the use of logical high and logical low in the present disclosure can be inverted.

[0172] In embodiments described above, the trigger is a push button 200 biased by a helicoid spring 220. However, the trigger may equally be a slider configured to move along a body of the powered device, or a rotatable knob. Similarly, the trigger may be biased into the first position by any other resilient means than a helicoid spring, such as a torsion spring, a resilient rubber, etc.

[0173] In the first embodiment described above, the magnet is affixed to the push button 200, such that a movement of the push button causes the same movement of the magnet. However, the push button 200 may alternatively be configured to indirectly cause a movement of a magnet located away from the push button. For example, the push button 200 may cause a translational movement of a rod or another element which is in contact with the magnet such that a movement of the rod causes a movement of the magnet. The trigger apparatus may be configured such that a small movement of the push button causes a larger movement of the magnet, thereby allowing the trigger apparatus to determine even small movements of the trigger by the user.

[0174] In embodiments described above, the predetermined event may correspond to the reception of the deactivation signal by the power module, the reception of the second deactivation signal by the power module, or the expiry of a timer after last reception of a second activation signal by the power module. Alternatively or additionally, the powered device may have an error detection functionality configured to interrupt power in case an error or fault occurs in the device, and the predetermined event may correspond to the reception, by the power module, of an error signal indicating that the device should be powered down.

[0175] In embodiments described above, the microcontroller 140 is configured to output one control signal (C1, C2, C3) for each phase of the motor which is received by the logic circuit 330, and the logic circuit drives both switching elements of a pair based on the same signal and the inverter 346.

[0176] Alternatively, as shown on FIGS. 8A and 8B, the microcontroller 140 may output a pair of control signals for each phase windings 352, 354, 356 of the motor, namely a first pair of control signals C1H and C1L, a second pair C2H and C2L, and a third pair C3H and C3L.

[0177] In each pair of control signals, only one of the control signals is output to the logic circuit 330, and the other control signal is used to control one of the switching elements in each pair of the motor drive 340 directly.

[0178] The logic circuit 330 performs separate logical AND operations on the activation signal A and each one of the control signals it receives, and the output of each AND operation is used to control the other one of the switching elements in each pair.

[0179] With this configuration, it is possible to cause the motor to brake without an interaction from the microswitch.

[0180] FIG. 8A shows the situation where the switching elements connected to the higher voltage terminal V+ are driven by the output of the logic circuit 330, while the switching elements connected to the lower voltage terminal V− are driven by the control signals output by the microcontroller 140 directly. However, as shown on FIG. 8B, the opposite situation may be used where the switching elements connected to the lower voltage terminal V− are controlled by the signals output by the logic circuit 330 while the switching elements connected to the higher voltage terminal V+ are controlled by the signals output by the microcontroller 140.

[0181] In embodiments described above, the switching elements are described as IGBTs 342, 344. However, as shown on FIGS. 8A and 8B, MOSFETS may be used as the switching elements, each MOSFET being connected in parallel with a diode (e.g. a regular diode or a Schottky diode).

[0182] In embodiments described above, the trigger apparatus is used in a power tool having an electric motor or an actuator. However, the trigger apparatus may be used in any other powered device, such as a remote controller for a remote controlled vehicle. In that case, the one or more control signals generated by the controller may be used to generate one or more radio signals to control the remote controlled vehicle.

[0183] In embodiments described above, the activation switch is a microswitch. However, it may alternatively be a reed switch or a binary Hall effect sensor.

[0184] In embodiments described above, the motor is described as comprising three phase windings. However, it would be understood by the person skilled in the art that embodiments described in the present disclosure may equally be used with motors having other configurations, for example motors having a different number of phase windings and/or a different number of rotor poles. Similarly, the WYE representation of the phase windings is illustrative, and the phase windings may also be described with a delta configuration instead.

[0185] All of the above are is fully in the scope of the disclosure, and are considered to form the basis for alternative embodiments in which one or more combinations of the above-described features are applied, without limitation to the specific combinations disclosed above.

[0186] In light of this, there will be many alternatives which implement the teaching of the present disclosure. It is expected that one skilled in the art will be able to modify and adapt the above disclosure to suit their own circumstances and requirements within the scope of the present disclosure, while retaining some or all technical effects of the same, either disclosed or derivable from the above, in light of his common general knowledge in this art. All such equivalent modifications or adaptations fall within the scope of the present invention as defined by the appended claims.

REFERENCE NUMERALS

[0187] 100: Trigger apparatus [0188] 110: microswitch [0189] 120: power module [0190] 130: linear Hall effect sensor [0191] 140: microcontroller [0192] 150: low-voltage power bus [0193] 1060: coil [0194] A: activation signal [0195] S: sensor signal [0196] C1˜C3, C1H˜C3H, C1L˜C3L: control signals [0197] 200, 1200: trigger [0198] 210: permanent magnet [0199] 220: helical spring [0200] 1230: magnetic shielding element [0201] P1: first position [0202] P2-1˜P2-n: second position(s) [0203] 300: electric sander [0204] 310: battery [0205] 320: power supply module [0206] 330: logic circuit [0207] 340: motor drive [0208] 350: electric motor [0209] 352-356: phase windings