TMCC and DCC

Given the characteristics of the two signals, while I can visualize that Legacy might run with DCC powering the rails, my guess is the signal would be significantly compromised by the EMI generated by the DCC track power waveform.  I don't think I'd even want to feed my Legacy this power...

In the above instance, the peak-to-peak voltage is around 30 volts with spikes well above that.  That's pretty ugly power to be feeding a Legacy locomotive, 19VAC is the max they're supposed to see, that's 27 V peak-to-peak.  It doesn't look like a great idea to me.

my NCE system only puts 15 volts to the rails no where near the 30 you mentioned. I followed up on this as Sinclar said he was running Legacy and DCC at the same time. thought it might be an option to convert older locos too. I run DCC on a On30 layout and its familiar to me. just kicking around some ideas. 

I mentioned it because that's what the 'scope says.   10 volts/division for three divisions is 30 volts.

I will take your word for it. way above my level of understanding. I just really like the flexibility of DCC and think it would be great if I could use it with the legacy. I only have one MTH loco and the rest are either factory TMCC/ Legacy or older units I have done ERR upgrades. hope they are profitable enough for third rail to keep producing. 

Well TMCC ain't happening on DCC power, that requires AC to function.  I'm surprised that Legacy runs on the DCC power, but I've never tried it, so I can't say what happens.

GRJ, there are some S gaugers who have both Legacy and DCC on their layout but switch the power source between a transformer and a DCC system depending on which engines they want to run. A few have tried running Legacy engines on the DCC supply, which is basically a square wave AC supply with a peak amplitude of 15V. With a true square wave the RMS voltage equals the peak voltage. Obviously the DCC square wave has harmonics up the wazoo. I am told the Legacy engines worked but did not see it with my own eyes. A challenge is the number of boosters needed along with the wiring configuration to run Legacy engines. My S gauge layout (Legacy only) has 80A total supplied to 8 independent power districts (two ZW-L's.) There are times with 6 trains running, some double headed plus lighted cars the layout draws 40A or more. I think DCC can be boosted to supply that amount of current but it is not a normal DCC configuration.

You can certainly switch track power sources for the various types of electronics, that's not an issue.  I believe the object of the exercise was running DCC and TMCC/Legacy at the same time on the same tracks.  That ups the ante.

@Rick Rubino posted:

Sinclar. followed your link here as suggested but did not find any info on TMCC and DCC running together. did I miss something somewhere. Rick

 

You must have.  I linked to this thread (Click the underlined words.) which I started to talk about MTH locomotives running DCC.  At the end of the 1st post I stated I'm using the NCE 10amp DCC system.  I did go in and adjust the booster to put out 18V, but I think I want to go back and tweak it down to match what the ZW-C is putting to the track which is closer to 16 volts.

Also in that first post I linked to my thread where I asked about running DCC and TMCC/Legacy, and later gave my results when I tried it myself.  The thread is here (Click the underlined words.).

As for running on the same track, DCC is a modulated AC output, not DC (Although my PS-1 equipped locomotives act just like DC locomotives do when on DCC track, they just sit there and the motor wines.  I have not tried a conventional AC motored locomotive yet.).  LC locomotives work in a DCC environment too.  I don't have LC+ or LC+2.0 locomotives, so I have not tested those.  But Percy and James go along just fine as I run my MTH locomotives.

Also, the Lionel Legacy sound cars, as well as the conventional sound cars all work fine in DCC (I have not tried firing the coupler on a VL reefer.).

I do not know about the O Gauge engines but the recent production S Gauge Legacy engines are designed to run on DCC and some S gauge operators do this. The only question seems to be will the Legacy engines made prior to built in DCC compatibility respond correctly to the Cab 2 commands when the layout is powered with a DCC system. The test information in the link seems to show that "it depends."

lionchief plus and flyerchief run well on dcc track power with the universal or dedicated controller

That's because they just need any sort of power, AC or DC, and all the control is done over-the-air.

Also use dcc and ac dcs and tmcc on same layouts but use double pole double throw switch to separate as needed

Just found this thread.  GRJ, couldn't you install a non-polar capacitor and/or zener diode in the Legacy loco, between the pickup rollers and the Legacy board stack, to smooth out some of those harmonics and reduce the peak voltage?  Since the TMCC signal goes through the air, it shouldn't affect communication with the CAB-2.

As you know I'm not an EE, just wondering aloud and hopefully prevent someone who wants to do both from frying their expensive Legacy loco.

Not a chance Ted, the damage to the signal is already done.  Remember, the track carries the other half of the TMCC signal.  TMCC locomotives actually depend on 60hz AC to operate, I am not positive about later Legacy with the RCMC, but Lionel is insistent on AC on the tracks for them as well.

The CAB2 to base signal is a non-issue, it's the 455khz track signal that's the problem, actually just one of the problems.

For track signal based TMCC/Legacy users who are interested in DCC, it would be better to add a wireless DCC system in order to avoid the power interference issues addressed in this thread. There are several wireless DCC systems available in both RF and bluetooth signal formats and with wireless, battery power becomes an option. DCC has been in existence a long time and offers an incredible array of options for running trains which is the primary reason for consideration of DCC.

Now that I've done a lot more running in mixed Legacy/DCC environment, there are some Legacy signal issues.  In some spots the Legacy signal disappears depending on the location of the DCC locomotives, if both DCC and Legacy are on the track at the same time.  This is parallel tracks, usually running DCC on one loop with Legacy on the other, but all track getting DCC signal.  If I switch the track the Legacy locomotive is on to be Legacy only, then the problem goes away.

What will be interesting is when the Lionel hybrid 4-4-0's come out as they are Legacy/DCC, and the manual doesn't say anything about a switch like MTH has on PS-3 locomotives.  So if both signals are on the track, which will it default to?  Maybe someone with an S gauge loco has tried it before as some Lionel S gauge Legacy locos were Legacy/DCC.  I do hope Lionel makes more O gauge Legacy/DCC locomotives in the future.

I am mostly into 3 rail but haveI an HO switching layout with NCE DCC , the power supply for it 

is 15 volts AC and my mult.i meter reads zero on the DC scale and 15 volts on the AC scale. I was always told that there was AC on the Rails of the DCC systems. if you put a non DCC loco on the rails it just buzzes, I am assuming that if it was DC it would just take off. my knowledge of electronics is basic so just my observations. Rick

I have quite a few of the newer AF by Lionel DC/DCC compatible S gauge engines. Unfortunately I do not have a DCC system. Any time the Legacy base is powered up and connected to the track the Legacy engine will be in Legacy mode and will respond to commands from the Cab2. It does not respond to track voltage variations. The only question is will one of these engines respond to the command from a DCC controller when the Legacy signal is on the track. There is a key difference between O gauge and S gauge. None of the S gauge Legacy engines have been built with Bluetooth. If the DCC compatible O gauge Legacy engines continue to have Bluetooth that could affect the response of the engine to multiple control inputs.

I wish I could help but unfortunately no DCC here.

The Lionel catalog uses the term "DCC enabled". Not sure what that means.

@BOB WALKER posted:

The Lionel catalog uses the term "DCC enabled". Not sure what that means.

It means you can use a DCC command system to control the locomotive.

Good input and should have been obvious to me. Am currently studying Lionel's S Scale DCC system in detail.