LED Interference

TypeHxfmr posted:

Hi,

This morning in the Rochester Democrat and Chronicle, the nationally syndicated car column Car Talk discussed LED interference on car radios from "cheap and poorly shielded LED systems." 

I was wondering if any model railroaders had experienced this problem on their remotely controlled railroads.

Take care,

Dick

others will explain it better but if you do not put something in the passenger cars the LEDs will degrade the MTH DCS signal.

What about TMCC or Legacy? Any reports or observations.

George Lasley

The LED systems they're talking about are using high frequency PWM to drive the LED's, it's the EMI generated by the square wave PWM drive that is the issue.

O I C 

Well! That certainly clears that up.😳

The lighting in our trains runs either on 60Hz AC or DC in the case of LEDS. This frequency is so low it shouldn't interfere with anything. PWM or pulse width modulation uses a very high frequency wave form and varies its width to adjust the brightness of the LEDs, high frequency so you don't see any flicker.

The issue with DCS is addressed by adding a choke into the circuit so it can't reduce the DCS signal. (See any  of the many discussions of this by GunrunnerJohn)

"What about TMCC or Legacy? Any reports or observations."

Lionel's command system(s) are almost always less prone to any kind of interference or signal problems than those from MTH. The architecture is different, and, though I'm probably not going to be as precise with this as some would like, a TMCC/Legacy system is far more reminiscent of a remote control model airplane radio system, and its robust broadcast signal/reception.

Besides the layout itself. All the recessed spot lights in my basement / train room are LED. Would that interfere with MTH signal?  PWM and EMI is beyond my span of lighting technology. 

Very doubtful.  There have been some reports of florescent lights affecting the TMCC system, I believe that's mostly the remote to base communication.  I personally had a forest of 4' florescent lights over the Legacy & DCS tracks, no issues came up here.