DCS/Legacy Interference

I have layout with both DCS and Legacy systems installed. It is all hooked up according to the Bible. With the DCS on MTH and engines run fine but the Legacy engines suffer from the blinking headlight syndrome. If disconnect the DCS system the Legacy engines run fine. They are on Parallel main lines with ground plane wires underneath and a temporary ground plane between the tracks. Any ideas why the DCS should effect the Legacy signal? 

Original Post

My experience is that the blinking lights issue with TMCC/Legacy engines is a TMCC/Legacy issue that exists whether DCS is operational or not.  I have more issues with TMCC/Legacy interfering with DCS and DCS engines not seeing the watchdog signal. For me the ground wire to earth ground was not a good connection when I had the TMCC/Legacy engines missing the signal with blinking headlights. 

The two signals don't mess with one another. Their frequencies are far apart. DCS is on the center rail and Legacy on the outer rails. Wiring track power for DCS will not affect Legacy.

Take an alligator clip jumper and put it somewhere on the track between the outer rails on one main line and try running the trains with both control systems powered up.

Both outside rails should be connected to common for Legacy. Also, the Legacy base track wire should be on the TIU out common or directly to the track.

Be sure that that you have the Legacy base power supply is plugged into a properly grounded receptacle. The house wiring is the other part of the Legacy system.

The ground plane wire is connected to earth  ground, not common, neutral AC or DC ground.

Carl

Arctic Railroad

Things to try:

  • Alligator clip from the legacy base directly to the outer rail
  • Grounded power brick for the Legacy base. (This one is a very common problem)
  • Dont use 2-prong cheaters
  • Do not connect any common to building/house grounding

What is your power source? Are you using a TIU and if so, what outputs?

Moonman, I do not do as you say "Both outside rails should be connected to common for Legacy. Also, the Legacy base track wire should be on the TIU out common or directly to the track."  I utilize gargrave and ross track and I just have the outside rail with the legacy signal.  No issues with Legacy or DCS.  I have wired the inside rail for isolation to indicate an occupied section of track (not implemented yet.)

winrose46 posted:

Moonman, I do not do as you say "Both outside rails should be connected to common for Legacy. Also, the Legacy base track wire should be on the TIU out common or directly to the track."  I utilize gargrave and ross track and I just have the outside rail with the legacy signal.  No issues with Legacy or DCS.  I have wired the inside rail for isolation to indicate an occupied section of track (not implemented yet.)

You are fortunate - you can keep both rails for Legacy signal using capacitors which won't affect the use of isolated sections.

One of Lionel's early Legacy signal videos  discusses this.

Kind of like not using blocks and one doesn't have issues with DCS. It's only a matter of time.

Carl

Arctic Railroad

Uh.... it's possible for DCS to be interfered with by TMCC/Legacy, but not the other way around (DCS jamming TMCC/Legacy).

DCS is an on-command signal (so it only sends something down the track if you push a button, and only for a few ms when you do). DCS is typically a 5-10V excursion when it's working. TMCC is a 450KHz RF carrier and is always there at about 10-100mV range. If the DCS excursion voltage gets low the TMCC can confuse the correlator in the DCS decoder, but the DCS packets are short and go by so fast the TMCC/Legacy train will just ignore them

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