Question on noisy vibration motor

[SimonAmpleman]

Hello,

I am using a PIC microcontroller to drive a LCD and a vibration motor.

Every components are supplied with 3.3V power supply that can supply up to 1A : AMS1117 3.3

The whole package run between 150 and 250 mA.

Everything is working fine except that when I activate the vibration motor, the LCD backlight loses half of its brightness and come back to its original power when the vibration motor is off.

The vibration motor is activated fully on and fully off from the microcontroller passing by a SI2302 N-Channel 1.25W, 2.5V MOSFET and protected with a SS14 Schottky Barrier Rectifier Diode against reverse voltage.

Could you give me some hints on what are the next steps to validate/protect/isolate to avoid this supply problem? If anything could be helpful to give more information, please ask and I will make sure to provide it quickly.

Thank you very much!

Simon

 

[D.A.(Tony)Stewart]

Can you tell if it is radiated, or conducted noise?

 

[SimonAmpleman]

Can you tell if it is radiated, or conducted noise?

Looks like conducted noise to me. I can see a ~0.8-1.0V variation on main 3.3V VDD with the oscilloscope with the motor in any orientation or position far from the PCB.

Thank you.

Simon

 

[chuckey]

You do not say what sort of DC(?) motor it is. If its a self contained BLDC motor it will take its current in short bursts, so a mean current of say, .1A actually means current burst of .3 A. If its a brushed DC motor then there will be sparking at its brushes. You wont go far wrong with a pair of .1MF capacitors from the motor terminals to the motor case with the motor case being earthed to the PCB, and a 500 MF cap across the motor drive connections at the PCB end.
Frank

 

[SimonAmpleman]

You do not say what sort of DC(?) motor it is. If its a self contained BLDC motor it will take its current in short bursts, so a mean current of say, .1A actually means current burst of .3 A. If its a brushed DC motor then there will be sparking at its brushes. You wont go far wrong with a pair of .1MF capacitors from the motor terminals to the motor case with the motor case being earthed to the PCB, and a 500 MF cap across the motor drive connections at the PCB end.
Frank

Thank you for your advise Frank. I will try this setup.

Simon