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Topic: Voltage for Vibration Motor (Read 1 time) previous topic - next topic

johnr

I know the output pins are 5v.  I plan on using PWM to drive a vibration motor.  Generally the motors I see readily available are rated for around 3.5 volts max.

Do I need to drop the voltage down?  Should I keep looking for vibration motors rated for higher voltage?

Thanks,

John

AWOL

You may want to find what sort of current the vibra takes.
The ones I use draw well in excess of the AVR's pin rating.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

johnr

Thanks...I will look into current draw.

Voltage should be OK than?

nikinick

I use the following setup supplying 4.5 V to a motor...works great!

http://lizarum.com/assignments/physical_computing/2008/motors.html

You should be able to control the motor/voltage out  as follows

int analogPin9 = 9;
int val = 0;       // variable to store the data

void setup() {
 pinMode(analogPin9,OUTPUT);  
 
}

void loop () {
 int val = 6;  // gives about 2.5 volts   when supplying ~5 volts
 /* val can be any number 0 thru 9 */
 {
    val = 28 * val;        // convert from 0-9 to 0-255
 
   analogWrite(motorPin,val);    

 }
}

johnr

Thanks for the info and the link...

I had thought that utilizing PWM (via analogWrite) did not change the voltage but turned the 5v on and off.  Is the 4.5v you mention is an "average" and that is OK as far as driving a motor needing less than 5V?

nikinick

The PWM (via analogWrite) is used to excite the transistor  (TIP120) which in turn swicth on the the voltage required for you load.  

You motor is connected to a external voltage source ( for motor that needs a lot of current  )or you can use the 5v from the arduino if your motor does not draw a lot of current. The other terminal of the motor is connected to the collector of the transistor.

Theory : excite the base of the transistor with pwm  will cause a voltage between the collector and the emitter which is grounded.

The more you excite the TIP120  the more volts to the motor.


retrolefty

#6
Nov 09, 2009, 04:40 am Last Edit: Nov 09, 2009, 04:41 am by retrolefty Reason: 1
Quote
I had thought that utilizing PWM (via analogWrite) did not change the voltage but turned the 5v on and off


Yes, PWM is either fully on or off at any given instant in time, however the duty cycle (percentage of on time Vs off time) does deliver more or less average power to the motor over time. The induction of the motor winding allows it to smooth out the highs and lows to a useful average power of 0 to 100% depending on the duty cycle of the PWM signal.

Lefty

johnr

Thanks to everyone that responded...a lot of good information here!

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