But at least I got an interesting teardown out of it! Unfortunately after disassembling my toothbrush I was unable to fix its problem. Some models even move the magnets from the toothbrush unit to the brush head. Surprisingly the different teardowns show a variety of microcontrollers, circuitry, and drive coils. I would have expected different models to be based on similar electronics that just changed the LEDs, buttons and software. The problem appears to be water seeping in around the shaft, eventually damaging the internals. Unfortunately, the brush has reliability issues-this was the second one to fail on me. It was designed with quality in mind, not low-cost production. Overall, I was surprised by how much electronics was inside the toothbrush, as well as the complexity of the drive mechanism. This prevents these components from draining the battery while the toothbrush is not in use.
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When the toothbrush is activated, a transistor energizes the LEDs and the LED driver chip, while another circuit powers up the pressure sensor. The microcontroller has a low power standby mode when it is waiting for a button press. The toothbrush is designed to conserve battery by using very little power when not in use. Voltage across the charging coil in a Sonicare toothbrush oscillates about about 80kHz. More details on the driver mechanism are here. This rotational vibration is transmitted to the toothbrush head by the torsion bar causing the head and bristles to vibrate. The mechanism limits the rotation to a few degrees, resulting in a rotational vibration back and forth rather than spinning like a motor. The magnet has poles on the front and back edges (perpendicular to the coils), so it will attempt to rotate back and forth to line up with the coil, along the long axis of the toothbrush. The coil constantly switches polarity so the north pole will switch from the top to bottom (the yellow and blue poles of the coil). The diagram below shows the driver mechanism disassembled. The result is the high-speed brushing vibration. The coil is pulsed one way to rotate the magnet one direction, and then pulsed the opposite way to rotate the magnet the other direction. The coil has two halves, wired in opposite directions, so the sides will have opposite magnetic fields. The toothbrush head is driven by an electromagnetic coil that moves a magnet. The driver mechanism and the H bridge circuit The resonator provides the clock signal for the microcontroller's timing. This is done during manufacturing through the large gold circles and triangle near the end The microcontroller is an off-the-shelf part, not a custom chip, so it needs to be programmed with the right software. The sensor is probably a Hall-effect magnetic field sensor. The back of the Sonicare circuit board contains the PIC16F1516 microcontroller chip. There are too many LEDs (10) for the chip to control individually, so eight of the LEDs are controlled by a separate LED driver chip.
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This chip contains the code for all the toothbrush functions: reading the buttons, lighting the LEDs, controlling the coil, and managing charging. The toothbrush is controlled by a mid-range 8-bit microcontroller, the PIC16F1516. The diagram below shows the components on the back of the circuit board. The number of test points (about 56) looks like overkill to me. During testing, spring loaded pogo pins on the test circuit make contact with these test points on the toothbrush board. For instance, each LED and each button has a test point that can be used to test the component. These are test points, allowing test connections to most parts of the board. The circuit board is covered with tiny gold circles.
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The tiny gold circles scattered across the board are test points for testing the board during manufacturing. The gold circles on the left are used to program the microcontroller chip. The circuit board for the Sonicare toothbrush is crammed with tiny parts. This connects the pressure sensor on the brush mechanism to the electronics board. Note the flexible brown ribbon cable between the center of the brush mechanism and the electronics board. The toothbrush still powers on in this state, as you can see from the illuminated LEDs. The photo below shows the brush mechanism partially disassembled and separated from the electronics. The long, thin circuit board (green) has the circuitry to operate the toothbrush.Ī white spacer sits on top of the circuit board, with holes for the LEDs and buttons. The battery (red, left) takes up about a third of the toothbrush.
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![century ac motor serial number lookup century ac motor serial number lookup](https://i.pinimg.com/564x/10/7d/5f/107d5fa8cbaf230a5cafd4747fe4fe40.jpg)
On the right is the vibration mechanism, which has a powerful magnet that is moved by the coil. In the center is the large red coil that causes the toothbrush to vibrate. The brush contains several key components, as can be seen above. The coil that vibrates the brush is in the center and the brushing mechanism is at the right. Inside the Sonicare toothbrush, top and bottom composite view.