I am doing my thesis work on "Peripheral Neuropathy assessment of Diabetic patients using perception of vibration".In which i use vibration motor to produce vibration with frequency 128 Hz. now i attach a tip(pin like structure) over the vibration motor.than there will be some amount of frequecy loss at the tip of pin.so is there any formula to calculate a frequency loss using area of pin ?or any other alternative way to calculate frequency loss.Hope for positive response.Kindly inform me as soon as possible.
Not sure what this has to do with Arduinos... but here my take.
Frequency loss: as long as you have the pen attached firmly to the motor, and can make sure the motor continues to run at 128 Hz (you have a speed controller?) the pen will also vibrate at 128 Hz.
The frequency of vibrations on one side of the pen is always the same as on the other side of the pen.
The amplitude of the vibrations may however be very different.
I use arduino board.and I use small coin vibration motor to produce vibration.and frequency remain constant 128 Hz. Now i want to make some(not same as that but something like that) pin like structure attached in figure 2(b) in below link. so you get brief idea.at the tip of pin will i get vibration with frequency 128 Hz? or loss frequency ? if loss than how can we calculate that? Hope for positive response.Kindly inform me as soon as possible.
A pin attached to a vibrating motor will vibrate at the same frequency (bar overtones).
Note that if you don't have any speed control of your motor you don't know the frequency, as the moment you attach the pin to the vibrator it is likely to slow down. Press that vibrating pin to someone's skin or so, and it's going to slow down even more.
Note that also amplitude may change, and that depends on the amplitude of the vibration the motor produces, the shape and weight of the object attached to it, and any external forces on it such as skin pressing against it.
As was pointed out there, without feedback you will not be able to ensure 128Hz or 128 x 60 = 7680 RPM.
An accelerometer on the motor would help, its signal would be pretty well noise free, being physically connected to the motor, the amplitude would be very high.
