Hi sorry for the long post

I have registered here to try and educate myself a little more on in a field i am not familiar with and point me in the right direction. Looking at the emf side of things and its very hard to know the difference between rf, emf etc for me.

Basically when a 12v control module controls the brightness of led mood lighting using a switching supply that varies the current, a magnetic field is given off the unit that gets stronger as the module drops the current. This magnetic field is traveling down the cables, Is this known as "back emf?"

I noticed when cables were put into the same trunking as the module, the field got a lot worse. Also the field readings are just as bad on the ground side. So would it be best to have power cables seperate from anything else? You google emf in google and its brain frying!

 

You google emf in google and its brain frying!

That is because you have to state a more definite frame of reference, BEMF is very application specific!
Max.

 

Hi thanks for your reply. i have googled and come up with more. I believe its pwm emi control i should be looking at?

 

Really understanding inductors and capacitors is enhanced by an understanding of some advanced mathematics. That said many people in the business acquire a non mathematical understanding of the behavior. For inductors it is encapsulated in the following for an ideal inductor with no DC resistance:

1. With no current flowing in an inductor there is no voltage across the inductor
2. Wit a CONSTANT current flowing in an inductor there is no voltage across the inductor
3. With a varying current flowing in an inductor, there is a voltage across the inductor the is proportional to the time rate of cange in the current. The constant of proportionality is the Inductance. The sign of the voltage is such as to oppose the flow of current. Hence the name "back emf", where emf is another name for voltage.
4. The current flowing through an inductor CANNOT change instantaneously