The body of my hair clipper consisted of just 2 pieces of plastic and a mechanical switch connected directly to the internal board. A detachable part (not shown in the picture) with two blades oscillates from side to side driven by the internal DC motor and a fancy spring. The electronics are as simple as it gets with just a classic AC->DC rectifier whose output is connected directly to a Mabuchi FK-290PY-051100 DC motor (100VDC, 6800RPM without load).
The motor has a cam attached that allows transforming rotary motion into linear motion for moving one of the two blades.
The board's circuit diagram is a classic that any electronics hobbyist should know. The input wave (mains electricity) is a SINE with 100V amplitude and a frequency of 50Hz (Tokyo). The 1MΩ resistor is used to increase the input impedance (ideally infinite). Then, a 100nF/125VAC ceramic capacitor is used to filter out noise from the mains signal. The result is rectified through a diode bridge (i.e.: a full-wave rectifier), and then smooth out with an electrolytic capacitor in parallel (a low pass filter). The output voltage is 98,88VDC instead of 100VDC because of the forward voltage (Vf≈0.56) of 2 diodes. In sum, here is the bill-of-materials (BOM):
- Resistors: 1x1MΩ, 1x150Ω
- Capacitors: 1x100nF (125VDC), 1x4.7μF (160VDC, electrolytic)
- Diodes: 4x1N4004-TP (Vf=~0.56)
- Motor: Mabuchi FK-290PY-051100 (~4 dollars)
- Plastic body
- Power cord
- Others: size attachments, oil, brush..