The problem starts with my 3D printer which is powered by a 12V SMPS. When it drives a heavy load such as heated base and hot end, it causes a ripple on the 12V rail. Also it affects the 5V rail with the same ripple as the image shows.
Note: My printer uses Ramp 1.4 with Arduino Mega2560
Note:
Chanel A is 5V from Arduino Mega, Chanel B is 12V from PSU.
For ramp1.4 , For Arduino Mega 2560
What I want to know is:
- How does this happen? As I know, voltage regulator should regulate all above 5V+(dropout voltage), so it should be a flat 5V line.
- How to fix or prevent this? (Do I need to add some component filter or change regulator ICs?)
Best Answer
You need to be extremely careful when probing noise and ripple as the unwanted signal may be on the ground because of where you are probing, not on the supply rail itself.
It is preferable to use the probe in the x1 setting not x10. And select a ground point very close to the supply you are measuring. The spring ground attachment you probably got with your probe is one way of helping that.
Is it causing a problem? If not it may not be real.
The scope trace shows about 200mV p-p ripple. That shouldn't affect the digital circuitry.