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Page 4 - Vibration motor

A vibration motor provides the ability to alert the wearer of any notifications silently. Use of the vibration motor is done sparingly since prolonged use will train the battery. If you do not want this feature, simply skip this section, and ignore future wiring associated with the motor. No negative effects will occur.

This may be the messiest soldering required. In a PCB version of the OSWatch, this would be one of the first parts moved to a board. Those new to electrical engineering may be tempted to simply wire the positive end of the motor to a OUT pin on the microduino, but this would be a bad idea. Each output pin on the microduino has a maximum amp output of around 40ma. The motor will draw 70-80ma. The circuit we will build solves this problem. For more information about this type of circuit, you can find a great tutorial -> motor tutorial.

As I mentioned, this one is messy, since we're cramming a handful of through hole components into a small space. First, here is the motor schematic

The Motor Schematic:

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1.) review schematic

This section will be a lot easier if you have familiarized yourself with this circuit. The end results will be 3 leads, 2 disconnected. The one connected lead will go to ground. The other two to be connected to power and a microcontroller pin in the future.

Parts laid out to match schematic

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2.) Connect the motor to the capacitor & diode

We begin by stripping a section of wire on each motor lead. Then we connect the capacitor and diode to the exposed wire. This keeps the logic as compact as possible.

Section 1 assembly

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3.) Assemble the transistor section

The transistor & a 1k ohm resistor (Brown, Black, Red) will be connected to the microduino control pin in the future. We solder the two together and use electrical tape to prevent shorts. A bit of super glue adds a complete seal and keeps the electrical tape from becoming unstuck.

Transistor assembly

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4.) Complete the circuit

The transistor collector pin joins withe the motor / diode / capacitor circuit. You need to make sure the length of this (motor to end of transistor) is less than the space width in the desired mounting location in the 3D printed Base. You will want at least a mm of clearance also (Don't forget the motor spins). You will also add the 33 ohm (Orange, Orange, Black) resistor on the opposite end of the motor / diode / capacitor section.

Completed circuit

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5.) Test the circuit

Nothing would be more depressing than skipping this, only to find out at the end the logic doesn't work. Also, once you glue this section into the base, it will be very hard to change. I have a spare Arduino Uno lying around. Simply follow the schematic and connect the VRegulator 3v3 pin (The 33 ohm Resistor pin) to 3v3 on the Uno, connect ground (the emitter pin on the transistor) to the Uno ground, and connect the 1K ohm resistor pin to a digital output pin (PWM works, but not required). You can download this shell application to test the motor here. Just change the MOTOR_PIN to the pin you choose, and run it. It should vibrate every second or so.

Testing

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6.) Install the module

When placing it in, make sure it is below the logic frame mounts, and make sure the motor weight (the metal part at the motor end) is not touching anything, and has some clearance. Then, add a few drops of glue to secure it. Once those drops have dried, spin the motor with a wire, or other object to make sure it can spin freely. Once you confirm that, add more superglue to completely secure the motor, without gluing the motor weight.

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Be careful not to glue the motor, or glue it too close to anything. Both would prevent it from spinning!

Installing the module

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You also want to wrap two wires around the battery (the ground and VReg feeds) You can solder the ground to the common ground pin from the power management system. You may need to use a bit of glue to keep the wires in check, but make sure the battery can properly fit. The VReg should be connected to a regulator feed in the future. Also, on the control pin (1K ohm resistor) you should add micro wire, and trim the resistor pin. This will make adding the logic frame easier in the future.

Guiding the wires

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7.) Verify the fit

As this is the end of building the watch base, you should once again verify the watch shell will still fit together. You will have to pass some wires through the button or screen holes. if all goes well, you should have a product that looks sorta like this:

Clean fit

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Next Page - Module Placement

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