1. Testing For EMF Created By Vibrations:
The VCM should be set on a flat, stable surface. Any vibrations made by the lens assembly should
be undisturbed. Set up a circuit and apply a current through the VCM so that the lens assembly is
pushed upward. Open the circuit loop and the lens assembly will begin to vibrate because it is
suspended by the spring system.
Materials:
Oscilloscope 7 pieces of wire Switch
Oscilloscope probe Variable DC power supply VCM camera module
Procedure:
1. Solder 2 wires to the VCM’s leads.
2. The oscilloscope has multiple channels of input. Attach the oscilloscope probe to the
oscilloscope’s Ch. 1 input.
3. Set up an electrical circuit like the one shown below. Set the variable DC power supply to 3.0V.
Connect the oscilloscope to the circuit from the Ch1 port. Set the oscilloscope’s Ch.1 horizontal
reading to 2.50ms and the oscilloscope’s Ch.1 vertical reading to 100mV. Set the
oscilloscope’s mode to trigger, and set trigger level to 0V. Close the circuit with the switch.

2. 4. Open the switch. The oscilloscope, when set to trigger mode, stops displaying electric signals
from the VCM as soon as voltage is 0. Immediately before the vibrations die out, the emf
generated by the VCM’s coil of wire will be displayed onscreen.

3. Data Analysis:
The waves displayed by the oscilloscope are irregular. I expected the emf be shown as damping
sine waves on the oscilloscope. It is be difficult to predict lens motion when the vibration of the lens
assembly is so abnormal. After scrutinizing the entire VCM structure, I discovered the reason for the
abnormal vibration of the lens assembly.
When the circuit is closed, a current is applied through the coil of wire, so the lens assembly will be
pushed upward by force generated along
the optical axis (1).
When the circuit is reopened with the
switch, the lens assembly will fall and
strike the base of the VCM (2). So, the
waveform displayed on the oscilloscope
is not displaying simple harmonic motion.
Instead, the waveform is recording the
irregular motion of the lens assembly
hitting the base of the VCM.
(1) (2)