Vibrating device

Other Hardware Motors, Mechanics, Power and CNC
1

Hello everybody,
I have an Arduino Mikrocontroller, however I am quite unexperienced with micoelectronics.
For a psychological experiment I'm searching for a very simple way of real-time controlling (on and off switching) two or three small vibrating devices (Perhaps this would do the job?: Vibration Motor - ROB-08449 - SparkFun Electronics).

The only but very important restiction that I have is that the vibrators should vibrate at a frequency of ~80hz.

To cut things short:
What would be the most simplest way to setup such a setting and what material do I need apart from my Arduino (and how to put it together)?
If you could give me direct product proposals this would be awesome and perhaps spare me a lot of time.
I would be very very thankful for any advice.

2

Ok, so you need a 3V source (couple of AA batteries) and a transistor to sink current from each one, such as AOI518 from digikey.com
http://aosmd.com/res/data_sheets/AOI516.pdf
Connect one motor lead to Battery +, the other to MOSFET Drain (D).
Connect Battery - to Arduino Gnd.
Connect MOSFET Source (S) to Arduino Gnd.
Connect Arduino PWM output pin (3,5,6,9,10,11) to 220 ohm resistor, then the MOSFET Gate (G).

Connect a button from Gnd to Arduino pin 4.
This will then make the motor vibrate at 80 Hz when the button is pressed for a "very simple way of real-time controlling (on and off switching)".

Add more buttons & transistors for up to 6 motors.

byte button4 = 4;
byte vibrate3 = 3;
void setup(){
pinMode (button4, INPUT_PULLUP);
pinMode (vibrate3, OUTPUT);
}
void loop(){
if (digitalRead (button4) == LOW){
analogWrite (vibrate3, 80);
}
else{
analogWrite (vibrate3, 0);
}

}
3

Hey CrossRoads,
thank you very much for your quick reply. As I am a complete newbie in this field, I have the following further questions:

(1.) What kind of vibrating motor would I need that would be working with your suggested setup? Can you also give me here some buying recommendations?

(2.) Am I right, that this MOSFET Drain is the transistor (AOI518) you are speaking of. If yes, are there alternative transistors that would do the same job? The problem is that I am from Germany and this AOI518 transistor does not seem to be available here...
Thank you again very much…

4

Look at specs for the transistor and find something comparable: logic level, low Rds with Vgs at 4.5V or less and high current capacity (many parts will say they are logic level, but only for 250microAmp - so not really useful), low input gate capacitance, N-channel MOSFET.
The motor, I just looked up what you had picked.
The basics will be the same no matter what motor/transistor you use.
One more thing - add a diode across the motor; anode to the transistor, cathode to the battery +. Needs to handle the same or higher current as what will be flowing thru the motor.

5

Hello CrossRoads,
thank you again for your reply.
Unfortunateley, I still have some questions:

(1.) Regarding the motor from sparkfun, are you sure that one can modulate the frequency of this motor?
For, in the user comments of this page, I found the following comments:

"can i connect that to a frequency generator and make it vibrate in range of 300hz to 5.0 khz ?
--> No, that will just make it vibrate weakly. PWM will change the power delivered to the motor, not the speed at which it rotates."

(2.) Regarding the Specs that you mention, I honestly do not understand what they mean.
Can perhaps someone here just mention me some alternative transistors that would do the same job?
Perhaps I have luck and one of these alternative transistors is also available in Germany....

(3.) For what do I need this diode? Isn't there direct current anyway?

Thank you again for your help.

6

The speed of an off-axis load motor depends on the mechanical impedance of its mount
as well as the supplied power - you will have to experiment with your set-up, this is
not something easy to predict.

7

Try this one

As to motor - did you want it to just spin, or did you want to virbrate? The virbrating ones usually have an unbalanced that makes it vibrate as it spins around. You could add your own off balance arm to a motor as well.

8

The motor will generate some current itself when the transistor stops conducting - that's a basic property of an inductor (the motor winding). The diode gives the current a path to dissipate vs creating a large voltage spike that can destroy the transistor.