What is this?

[BatteryCharger]

I'm going to use a Dell laptop power supply as a bench supply with an LM317 regulator. On the end of the cord, about 2 inches before the tip there is a big "thing". What is this? I see it on alot of electronics cords.

 

[Big_Ed]

Maybe some sort of electrical interference filter? I've often wondered the same thing.

 

[enLIGHTenment]

It's a ferrite core interference filter. It's to block radio frequency electrical noise from escaping from the computer and radiating from the cable. This is to prevent radio interference in the immediate area.

 

[PhotonWrangler]

What EnLIGHTenment said! You'll sometimes see those on the ends of VGA cables, AC power cables, etc. They also call them ferrite chokes because they choke off the EMI/RFI.

 

[BatteryCharger]

So it's no problem cutting it off then to make my power supply? /ubbthreads/images/graemlins/smile.gif

 

[PhotonWrangler]

Nope, not at all. But it's no problem leaving it on either. It's not actually wired in the circuit - it's clamped around it.