I want to run a TMCC engine conventionally on an isolated upper loop of track while the lower loop is connected to a cab1L base. Can you short the antenna to the AC ground or the DC ground??
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You don’t have to do anything to a TMCC engine to run conventional. Set it on the tracks, make sure the switch is in RUN and it will go. ......don’t short out anything! It’ll automatically know whether it’s on a conventional track or a Command track.......Pat
harmonyards posted:You don’t have to do anything to a TMCC engine to run conventional. Set it on the tracks, make sure the switch is in RUN and it will go. ......don’t short out anything! It’ll automatically know whether it’s on a conventional track or a Command track.......Pat
If hes got a cab 1 base plugged in. Even though its not connected to the conventional loop the loco will sit there waiting for commands from the remote.
One side of the Tmcc/Legacy system signal is transmitted through the ground wiring of your train room via the ground lug on the command base wall wart.
RickO posted:harmonyards posted:You don’t have to do anything to a TMCC engine to run conventional. Set it on the tracks, make sure the switch is in RUN and it will go. ......don’t short out anything! It’ll automatically know whether it’s on a conventional track or a Command track.......Pat
If hes got a cab 1 base plugged in. Even though its not connected to the conventional loop the loco will sit there waiting for commands from the remote.
One side of the Tmcc/Legacy system signal is transmitted through the ground wiring of your train room via the ground lug on the command base wall wart.
Yep, your right Rick, I saw isolated and had a brain fart....
If you connect the locomotive antenna to the frame, you'll turn off TMCC for that engine. 
My question is why? Just run it with tmcc.
Dave
Thanks for all the replies. The reason for not wanting TMCC on is that level of the layout is controlled by a stepper switch that sequences 4 passenger trains on various sidings. The post war engines are run with the e-unit locked out. Just wanted to run some of my newer engines on that level.
Given what GRJ said, if you wanted to get fancy, you could add an SPDT switch in line with the antenna. One way would be to the antenna (TMCC on), and the other would be to ground (TMCC off).
BTW, I like the sound of what you're doing on that upper level. I used to do stuff like that on my portable layout at shows, only with relays. (pre-TMCC days)
It just occurred to me, even if you ground out the antenna, you'll still have the problem of locking it in forward. I'm not sure how you overcome that one.
This is a long shot, but if you used a DPDT switch and a rectifier you might be able to bypass the electronics altogether and hardwire the motors in forward. The other side of the switch would feed power to the electronics for TMCC mode. You might need some diodes on the motor leads from the board to prevent feedback into it.
It begs the question, how badly do you want this?
I am thinking that the program switch in the program position locks the engine in forward under conventional operation. Grounding the antenna will prevent the engine from entering the program mode.
Big_Boy_4005 posted:Given what GRJ said, if you wanted to get fancy, you could add an SPDT switch in line with the antenna. One way would be to the antenna (TMCC on), and the other would be to ground (TMCC off).
.........
I wonder if it might be better to put the switch at the end of the antenna if trying this? My thought being that if you are grounding the signal, then extra wire to achieve the grounding (switch to additional wire to ground) probably would not matter, but if you were to put the switch before the antenna, the wire you use to get from the board pin to the switch very well may act like an antenna itself, thereby defeating the purpose.
In a slightly different thought, I seem to recall once when I had a TMCC engine(maybe it was Legacy, but the same idea for the purposes here, I believe) disassembled for some sort of maintenance, I had a momentary lapse of thought and put it on the track for testing while still partially disassembled. I noted about an instant after powering up that the antenna was not connected (might have been attached to the shell, so I had disconnected it for whatever I was doing). To my surprise, the engine still operated in TMCC mode, IIRC (i expected it to take off at full speed, or at whatever speed it would achieve for where I had the transformer set). My point is that a TMCC engine may see the signal even with no antenna connected. (though I am sure John is right that if you actually connect the antenna pin to ground, you will effectively kill the TMCC reception). It would probably not function well with no antenna, but it may be enough to keep it from thinking it's in conventional mode.
Big_Boy_4005 posted:It just occurred to me, even if you ground out the antenna, you'll still have the problem of locking it in forward. I'm not sure how you overcome that one.
This is a long shot, but if you used a DPDT switch and a rectifier you might be able to bypass the electronics altogether and hardwire the motors in forward. The other side of the switch would feed power to the electronics for TMCC mode. You might need some diodes on the motor leads from the board to prevent feedback into it.
It begs the question, how badly do you want this?
Assuming the engine can't see a TMCC signal, doesn't the run/program switch function as a directional lock in conventional mode? I'm pretty sure that's universal since the original days of TMCC.
-Dave
So here's some thoughts,
First, I think others are correct that the run/prog switch acts like a direction lock in conventional.
Depending on the engine(s) in question, and if they use one, it might be easier/cleaner to replace the R2LC with a conventional direction board, converting it into a non-tmcc engine.
The last thought is, and I realize this may be beyond what you want to do, but to use a micro-controler to interface between the conventional layout and the TMCC system. This could be done in a 'better'way that could speed up and slow trains and keep them powered on the sidings, but for a simple solution, about $10 in parts and an evening of coding for someone familiar with how to do it, could make a piece of hardware that plugs into your command base and every couple seconds tells the the engines on that part of the layout to move forward at X speed. Then all you would need to do is set the engine ID of the engines on that part of the layout to the correct settings and likely not have to make any other changes to engine or layout.
As a thought you could put all of the engines on that section into one train so you can just add and remove engines from the 'lash-up' when you want to use them there. In pseudo code the thing would be a program something like:
send out direction forward to train 1
send out relative speed +32 to train 1
Wait 1 second
Repeat
Rogerdodger posted:I am thinking that the program switch in the program position locks the engine in forward under conventional operation. Grounding the antenna will prevent the engine from entering the program mode.
Not true, it won't have any effect on the PGM/RUN switch operation.
The engine will run just fine with an exposed R2LC board. The antenna trace on the board to the connector, thru the trace on the mother board is several inches. I'm guessing that it doesn't matter where you ground the antenna since the wavelength of the signal is over two thousand feet.
As for the ungrounded antenna, I once had an engine with a cut in the trace on the R2LC board and it ran without the boiler in place. In that condition, the antenna was about an inch long.
RickO posted:harmonyards posted:You don’t have to do anything to a TMCC engine to run conventional. Set it on the tracks, make sure the switch is in RUN and it will go. ......don’t short out anything! It’ll automatically know whether it’s on a conventional track or a Command track.......Pat
If hes got a cab 1 base plugged in. Even though its not connected to the conventional loop the loco will sit there waiting for commands from the remote.
One side of the Tmcc/Legacy system signal is transmitted through the ground wiring of your train room via the ground lug on the command base wall wart.
Actually Pat had it right. It takes two wires to complete a circuit. House ground is only one side. The other is the U terminal on the command base. As long as the OP uses a separate transformer on the isolated loop there won't be any connection to the U terminal on the base.
Our club has a test track with no connection to the main layout and its own transformer. As long as no base is connected to it, it does not respond to TMCC signals.
So two options. Ground the engines antenna or use a separate transformer.
Pete
cjack posted:The engine will run just fine with an exposed R2LC board. The antenna trace on the board to the connector, thru the trace on the mother board is several inches. I'm guessing that it doesn't matter where you ground the antenna since the wavelength of the signal is over two thousand feet.
As for the ungrounded antenna, I once had an engine with a cut in the trace on the R2LC board and it ran without the boiler in place. In that condition, the antenna was about an inch long.
Good points. While I was worrying about having a proposed wire from board to switch act as an always present antenna, I forgot to account for the traces on the board itself. Ooops!
I wasn't trying to go into wavelengths when I suggested the end being a better point to have the proposed switch, I was just forgetting that no matter what was done, the board would still have a bit of an antenna present no matter what(unless significantly modified).
I think by discussing this we are validating that there is quite a difference between optimizing positive operation (i.e., having a TMCC engine respond reliably when the signal is present - which is aided by the antenna included), and guaranteeing negative operation (i.e., it's a lot harder to make the electronics NEVER see the command signal without seriously modifying them - removing the item labeled as antenna is probably not enough)
-Dave
Given the fact that TMCC stuff will run with no antenna connected, grounding the antenna is the sure-cure. If it's grounded, I can assure you, it won't run under TMCC control.
