Hi! I am trying to control multiple vibration motors with PWM through one transistor (and one microcontroller pin). I want all the motors to behave identically. I am working on a passed-down project, and using a circuit designed by someone else (but with expertise). The circuit functions well for one motor, but when I attach a second motor in parallel the voltage drop across the motors decreases and they vibrate at a much smaller amplitude. A schematic of my circuit is attached. I am using the following parts:
Why does the voltage drop across the motors change when more motors are added in parallel? Is it because the max drain current of the transistor is not adequate for two motors? If I am controlling with PWM am I limited by the continuous or pulsing max?
What is the function of the resistor in parallel with the transistor? Is it only there to diminish the current reaching the transistor from the microcontroller?
Could I successfully control 2+ motors at max amplitude if I use a transistor with a higher max Id?
and using a circuit designed by someone else (but with expertise)
Alas not.
There is no base resistor, there needs to be one.
Use a higher rated transistor like 2N2222 for a higher load, something like 150 ohm
base resistor to get reasonable saturation. Two motors ought to pull 240mA, so about 30mA
base current is ideal (and about the most you should contemplate driving from an Arduino pin)
Not really, it helps it turn off a little better, something like 1k would be reasonable (not sap too much
base drive current).
Bipolar transistors like this need to be driven hard to saturate well (small voltage between collector
and emitter when on, like 0.2V or less). If the transistor has a gain of 200, that counts for nothing,
it will need about 5 to 10% of the collector current fed to the base to saturate - this is not the
same operating region as normal analog amplification.
hello i am also trying to control 10mm vibration motor with single PWM pin. So i just want to know after using higher rated transistor like 2N2222 are both motors still vibrating at smaller amplitude or is there any improvement after using higher rated transistor like 2n2222.
If not can anyone give me solution how can i controll two 10mm vibration with single PWM pin.
Motor 10mm coin type vibration motor:
operating voltage 3V max 3.3V
operating current 60mA max 90mA
