Pressure sensing system and method for an electric toothbrush
A pressure feedback system continuously monitors the level of pressure or force on a brush head and is programmed to provide a feedback signal to a user based on the amount of pressure. The pressure level is monitored as a function of the change in the speed of the drive shaft. The system includes a housing, a motor, a drive shaft for attachment to a brush head, a feedback device, a sensor capable of detecting a change in the rotational speed of the drive shaft, and a microprocessor. The microprocessor is programmed activate the feedback device as a function of the measured change in rotational speed. The sensor may be a Hall effect sensor, or another sensor that is responsive to a magnetic field. A magnet may be positioned on the drive shaft, or another portion of the system that moves as a function of the drive shaft.
1. A system for determining an amount of pressure applied to a brush head, and for providing feedback to a user upon a measured pressure reaching a predetermined threshold, the system comprising:
a brush head;
a drive unit connected to the brush head, the drive unit having a drive shaft that is activated to move the brush head with respect to the drive unit;
a magnet that moves in a repeating manner as a function of the movement of the drive shaft;
a Hall effect sensor that generates a signal based on the movement of the magnet;
a feedback device; and
a microprocessor connected to the Hall effect sensor and the feedback device, the microprocessor programmed to activate the feedback device as a function of a change in speed of the movement of the magnet;
wherein the movement of the drive shaft is rotational
wherein the movement of the drive shaft is rotary oscillating about an axis; and
wherein the microprocessor generates a signal based on the change in rotational speed of the drive shaft.
2. The system of claim 1 wherein the microprocessor is programmed with a threshold change in rotational speed, such that the microprocessor generates a signal based on change in rotational speed meeting the predetermined threshold.
3. The system of claim 2 wherein the threshold is between about 5000 and 7000 RPM.
4. The system of claim 3 wherein the threshold is about 6000 RPM.
5. The system of claim 4 wherein the feedback device is one of a light emitting device, an audible device and a haptic device.
6. The system of claim 5 wherein the feedback device is positioned on the drive unit.
7. The system of claim 6 wherein the brush head includes a neck having a first end connected to the drive unit and a second end supporting a bristle carrier, the brush head including a brush shaft that is driven to rotate about a first axis by the drive shaft, the bristle carrier being driven to rotate about a second axis by the brush shaft.
8. A pressure feedback system for a brush head comprising:
a brush head;
a drive unit connected to the brush head, the drive unit having a drive shaft that is activated to oscillate the brush head with respect to the drive unit;
a magnet that oscillates as a function of the movement of the drive shaft;
a sensor that generates a signal based on the oscillation speed of the magnet;
a feedback device; and
a microprocessor connected to the sensor and the feedback device, the microprocessor programmed to activate the feedback device as a function of a change in speed of the movement of the magnet;
wherein the movement of the drive shaft is rotational; and
wherein the microprocessor is programmed with a threshold change in rotational speed of the drive shaft, such that the microprocessor activates the feedback device based on change in rotational speed meeting a predetermined threshold.
9. The pressure feedback system of claim 8 wherein the brush head includes a brush shaft and a bristle carrier, the brush shaft connected between the drive shaft and the bristle carrier.
10. The pressure feedback system of claim 8 wherein the magnet is connected to the drive shaft and the sensor is fixed in position with respect to the magnet.
11. The pressure feedback system of claim 8 wherein the threshold change is a change in speed between about 5000 and 7000 RPM.
12. A pressure feedback system for a brush head comprising:
a housing;
a motor within the housing;
a drive shaft connected to the motor and having a portion extending from the housing for attachment to a brush head, the drive shaft operable to rotate at a rotational speed upon activation of the motor;
a feedback device;
a sensor capable of detecting a change in the rotational speed of the drive shaft; and
a microprocessor connected to the sensor and the feedback device, the microprocessor programmed to send a signal to activate the feedback device as a function of the change in rotational speed of the drive shaft detected by the sensor;
wherein the brush head includes a brush shaft connected to the drive shaft and a bristle carrier connected to the brush shaft, wherein rotation of the drive shaft causes rotation of the brush shaft and the bristle carrier; and
wherein the sensor detects a change in rotational speed of the drive shaft resulting from a force on the bristle carrier.
13. The pressure feedback device of claim 12 wherein the microprocessor is programmed to send the signal to the feedback device upon a change in the rotational speed of the drive shaft exceeding a predetermined threshold.