A small DC motor is used to generate vibrations as a cause of its displacement due to its rotating shaft being attached to a non symmetric mass. It can be used for multiple applications as a result of its adaptable and resourceful uses, including but not limited to - a body massager, as an engraver on various materials, for recreating various items that utilize rotation-oscillation like electric toothbrushes and lastly from an educational point of view for learning how vibration motors work and how they create vibrations.
Step 1: Understanding the Principle
This vibration motor is a DC motor with an offset (non-symmetric) mass attached to the shaft.
As the shaft rotates, the centripetal force of the offset mass is asymmetric, resulting in a net centrifugal force, and this causes a displacement of the motor. With a high number of revolutions per minute, the motor is constantly being displaced and moved by these asymmetric forces. It is this repeated displacement that is perceived as a vibration.
There are two aspects of the vibration commonly quoted, the Vibration Amplitude and the Vibration Frequency-Vibration Frequency - The frequency of vibration is fairly easy to figure out. Motor speeds are quoted in revolutions per minute, or RPM. Vibration Frequency is quoted in Hertz(Hz), which is one cycle per second As there are 60 seconds in a minute, we can divide the RPM by 60 to get the vibration frequency in Hz.
Vibration Frequency(Hz) = RPM/60
Vibration Amplitude - Essentially, the force is dependent upon the size of the mass, the distance between the mass centre of gravity and the motor shaft and the speed of the motor.The total vibration amplitude also depends on the size of the object the motor is attached. For example, the small vibration motor in a phone would not cause much displacement if attached to a heavy object like a desk.
The strength of the force generated by the motor is described in the following equation :
F(centripetal force in newtons)= m (the mass of the offset or eccentric mass in kilograms) * r (the eccentricity in meters or the radius of the mass from its center) * ω(the angular velocity in rad/s)^2 ...(1)
If we know the force from the vibration motor and the size of the target mass we can calculate the acceleration of the system using Newton's Second Law . Vibration Amplitude is actually a measurement of acceleration, given by a.
F = mass * acceleration = m (the mass of the offset or eccentric mass in kilograms) * r (is the eccentricity in meters or the radius of the mass from its center) * ω(the angular velocity in rad/s)^2 .................From (1)
Step 2: Materials
Common household supplies and some basic electrical inputs are required for this demonstration:
1) DC motor
2)An offset mass for attaching it to the dc motor's shaft. I used some epoxy glue (mseal) to mould it and form the right shape
3)a battery pack or any other form of dc power.
6)*optional* a cover for the whole system
Step 3: Assembly
- Attach the offset mass to the motor shaft.
- Connect the motor terminals to the power supply using the wires and use a switch somewhere in between.
- Encase the apparatus
Step 4: Applications
- A body massager
- As an engraver on various materials by attaching it to a sharp object
For recreating various items that utilize rotation-oscillation like electric toothbrushes
Lastly from an educational point of view for learning how vibration motors work and how they create vibrations.
Step 5: This Is My Submission for the RYSI Awards
To whomever it may concern ,please find attached this submission along with my contest form.