Author Topic: Oscilloscope pick up noise from power line  (Read 548 times)

0 Members and 1 Guest are viewing this topic.

Offline chancs

  • Contributor
  • Posts: 16
  • Country: au
Oscilloscope pick up noise from power line
« on: October 02, 2019, 11:35:56 am »
When I turn on the LED overhead light, my oscilloscope picks up the switching noise (they are only the same power outlet). I tried to reallocate the LED light to a different outlet, the switching noise is reduced by 50%, still noticeable. Below are some screen captures showing the waveform when the LED light is turned on and is turned off.


LED OFF


LED ON

Is there any product on the market that can reduce the switching noise?
 

Offline Ian.M

  • Super Contributor
  • ***
  • Posts: 8274
Re: Oscilloscope pick up noise from power line
« Reply #1 on: October 02, 2019, 11:55:22 am »
Yep.   Incandescent, or line frequency magnetic ballast fluorescent lighting!  >:D

For low voltage lighting, avoid SMPSUs and PWM dimming. 'Dumb'  LED strips  on a linear PSU are acceptable.
 

Offline chancs

  • Contributor
  • Posts: 16
  • Country: au
Re: Oscilloscope pick up noise from power line
« Reply #2 on: October 02, 2019, 02:38:48 pm »
So I should better off replay the LED light with traditional filament light? Is there any energy efficient light source that would interfere with my scope?
 

Offline ferdieCX

  • Regular Contributor
  • *
  • Posts: 152
  • Country: uy
Re: Oscilloscope pick up noise from power line
« Reply #3 on: October 02, 2019, 02:49:41 pm »
I had the same problem 5 years ago, the power brick of the LED bar interfered with the trigger of my scope.
My LED bar (Diodor brand) is specified to work between 10 to 14 V so, I made a simple power supply with a 9 V + 9 V transformer, two diodes
and a filter capacitor calculated to have less than 1 Vpp ripple. This way, the bar gets a voltage that roughly varies between  11 and 12 V.

There is also a thread about this problem:

https://www.eevblog.com/forum/beginners/oscilloscope-interference/?topicseen
 

Offline JustMeHere

  • Regular Contributor
  • *
  • Posts: 235
  • Country: us
Re: Oscilloscope pick up noise from power line
« Reply #4 on: October 02, 2019, 05:17:39 pm »
https://youtu.be/ty_sxMxUWeU

Dave did a video on this
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf