Newbie question on DCC

[OgreMike]

I'm sure there are, or maybe just do a consist.

Yes! I’m looking forward to doing a consist as opposed to just a single motorized unit with a dummy or two behind! Looking forward to some sounds, as well!

 

[OgreMike]

Small Red Flag went up when I read this. It might just be the words you used, but just in case:

If you are talking true transponding, that is a Digitrax proprietary system. Not all decoders can transpond.

The NMRA recommended practice (S-9.3.2) for DCC reverse communication is called "Rail Com". It is brought to us by the same people that invented DCC, the Lenz company.

And just to be more clear, I don't know anyone who uses either. The museum uses the Bruce Chubb C/MRI system for block occupancy for the dispatcher.

On the other hand, if you are just talking about block occupancy detection that is generic across companies. I think every one makes a block detection that can be used in conjunction with other systems.

Hey Iron. Thanks! Wow . . . there’s a lot to digest here! You’ve obviously got way more knowledge at an intricate level than I. When it comes to transponding and transponders, I’m familiar with the mechanism, and how it works with regard to radar from having flown planes for a number of years. Transponders with regard to flying are electronic mechanisms that put a very distinct tag on each airplane within a radar screen for the controller to more easily direct traffic, but you can also get a simple paint of your aircraft on a radar screen. It’s definitely not the preferred method for airtraffic control, but it does happen.

For a layout like the one I’m working on, I see no need for transponding in the truest electrical sense. Rather, I would just like to have simple block occupancy via the “paint” of a train with its cars behind in a given power district (I think Digitrax refers to theirs as “detection sections”).

I’m actually very glad you brought this subject up, Iron. I just received the pair of PM-74s from Digitrax yesterday in the mail. For anyone who’s interested, a couple observations: first, they don’t include a back up power supply with the unit. I guess the unit can run on loco net (which I have yet to totally understand) but a back up power supply is necessary for good and continuous, consistent operations. The PS – 14 power supply is available for about 20 extra dollars depending on who you turn to. Second, they make a reference in their instruction manual to an “optional” LT5 tester/LED unit. The LT5 is supposed to, per my understanding, attach directly to a 10 pin output on the lower left section of the PM 74, however, the LT5 is not included with the unit! And, when I inquired of DigiTrax tech-support about how to obtain an LT5 unit, they rudely dismissed me and told me that they don’t sell it separately. They also told me rather dismissively as well, that I could simply “build my own 10 pin ribbon cable“ to take advantage of the capabilities of the LT5 and these 10 pins it sits on to build my own detection system!

So having given all this background, do you or anyone here on the forum have any experience with the PM74? Are there, in fact, 10 pin ribbon cables available commercially that would plug right in to these pins? If that much is available, perhaps I COULD build a simple detector system based on the outputs from these 10 pins that could give me a simple “paint” detection of occupancy in a section of track? Comments most welcome! Mike

 

[Iron Horseman]

Hey Iron. Thanks! Wow . . . there’s a lot to digest here! You’ve obviously got way more knowledge at an intricate level than I. When it comes to transponding and transponders, I’m familiar with the mechanism, and how it works with regard to radar from having flown planes for a number of years. Transponders with regard to flying are electronic mechanisms that put a very distinct tag on each airplane within a radar screen for the controller to more easily direct traffic, but you can also get a simple paint of your aircraft on a radar screen. It’s definitely not the preferred method for airtraffic control, but it does happen.

For a layout like the one I’m working on, I see no need for transponding in the truest electrical sense. Rather, I would just like to have simple block occupancy via the “paint” of a train with its cars behind in a given power district (I think Digitrax refers to theirs as “detection sections”).

Good, that is what I was hoping you were talking about.
I guess you could say the difference on your control panel would be that a transponded train would tell you exactly what channel number loco(s) were operating there, while a detected control panel just indicate there is some generic train there.

I can't help you with the specifics of the PM-74, other than to say that has been my experience with Digitrax also. They seem to be a bunch of egg head technos and expect everyone else to be also.

 

[OgreMike]

Good, that is what I was hoping you were talking about.
I guess you could say the difference on your control panel would be that a transponded train would tell you exactly what channel number loco(s) were operating there, while a detected control panel just indicate there is some generic train there.

I can't help you with the specifics of the PM-74, other than to say that has been my experience with Digitrax also. They seem to be a bunch of egg head technos and expect everyone else to be also.

Yes, I’m starting to get that impression also. Since my earlier post, I’ve discovered that they market a 10 pin ribbon connector kit with a meter of 10 wire ribbon cable that’ll probably be what I need to put in some simple block occupancy lights on the control panel. I believe it’ll work with the 10 pin LED outlet for occupancy detection on the left front of the PM74.

 

[flyboy2610]

No, I wanted the Digitrax as that is the system my friend has and our club here that I go to most.

Going with what you have local support for is always a good idea.

 

[OgreMike]

Anybody like to solder the ends of their wires before applying screw-down pressure in a terminal connection? The braided flex wire I’m using seems to pull out too easily even though I’m tightening the screws on the terminal as much as I can!

 

[flyboy2610]

Anybody like to solder the ends of their wires before applying screw-down pressure in a terminal connection? The braided flex wire I’m using seems to pull out too easily even though I’m tightening the screws on the terminal as much as I can!

Are you talking about terminal blocks/
https://www.amazon.com/Positions-Te..._bs_306708011_sccl_1/141-9118222-9542754?th=1

For those I use spade connectors.
https://www.menards.com/main/electr...000-c-6447.htm?tid=1236254054493017027&ipos=1

 

[Smudge617]

Anybody like to solder the ends of their wires before applying screw-down pressure in a terminal connection? The braided flex wire I’m using seems to pull out too easily even though I’m tightening the screws on the terminal as much as I can!

I usually strip a section and double or triple the bare wire before soldering, depends on the gauge I'm using, or as flyboy2610 mentioned use a spade connector.

 

[OgreMike]

Are you talking about terminal blocks/
https://www.amazon.com/Positions-Te..._bs_306708011_sccl_1/141-9118222-9542754?th=1

For those I use spade connectors.
https://www.menards.com/main/electr...000-c-6447.htm?tid=1236254054493017027&ipos=1

Thanks Flyboy! Yeah, I’m using the spade connectors now! .
BTW, new question for anyone who wants to chime in. I just ran my first two analog Locos on my new DCC controlled mainline. I was able to get them to run, however, even at 99% speed, they ran kind of slow and haltingly. My F7A diesel ran only about 15 mph max at scale. Is there a way to increase voltage from the command station/booster? FYI, I’ve run track power leads from the applicable power busses approximately each 5 feet of track. Wire to busses from command station is 16. From busses to power feed connections is 18. Layout is 12x8. Please opine all! Thank you!
Mike

 

[OgreMike]

I usually strip a section and double or triple the bare wire before soldering, depends on the gauge I'm using, or as flyboy2610 mentioned use a spade connector.

Thanks Smudge. Sorry for the late reply! See my reply back to Flyboy about slow performance.

thanks
Mike

 

[Smudge617]

Thanks Flyboy! Yeah, I’m using the spade connectors now! .
BTW, new question for anyone who wants to chime in. I just ran my first two analog Locos on my new DCC controlled mainline. I was able to get them to run, however, even at 99% speed, they ran kind of slow and haltingly. My F7A diesel ran only about 15 mph max at scale. Is there a way to increase voltage from the command station/booster? FYI, I’ve run track power leads from the applicable power busses approximately each 5 feet of track. Wire to busses from command station is 16. From busses to power feed connections is 18. Layout is 12x8. Please opine all! Thank you!
Mike

That's because your running a DC loco and the power on the track from a DCC throttle is AC, you'll get a hum from the loco's too when stationary, that's because the motor armature is going slightly forwards and backwards at a high rate, which is what that sound is, I wouldn't advise you to have the loco's stationary for any length of time as that can damage the motor, get a decoder in it (even a cheap one like a Laisdcc if you want to run it with a DCC throttle) or disconnect the DCC throttle and use a DC controller if not you may end up having to re motor your loco's.

 

[OgreMike]

Wow, thanks greatly Smudge! Your reply says it all! Why don’t the folks at Digitrax tell a person these sorts of things?? It would have been great to know this sort of thing, as in their manual, they definitely talk about running an analog engine FIRST! But they don’t mention anything about the attendant halting performance! Thanks a bunch Smudge! Thankful to have all of you on here to help this newbie train freak! . Mike

 

[Smudge617]

Wow, thanks greatly Smudge! Your reply says it all! Why don’t the folks at Digitrax tell a person these sorts of things?? It would have been great to know this sort of thing, as in their manual, they definitely talk about running an analog engine FIRST! But they don’t mention anything about the attendant halting performance! Thanks a bunch Smudge! Thankful to have all of you on here to help this newbie train freak! . Mike

They assume you've installed a decoder (otherwise why have a DCC throttle), if a decoder is installed, it will run on either DC or DCC unless you've told the decoder to run on DCC only

 

[Smudge617]

The bit about running on analogue (I think) is again assuming you have a DCC ready loco with the blanking plate still installed, always worth remembering if you have a problem with the loco as you can remove the decoder,and replace the blanking plate, if the loco will run on DC, the problem is usually with the decoder, if it doesn't the loco has the problem.

 

[Smudge617]

Weirdly I've found with older analogue loco's they run much better with a decoder than without.

 

[OgreMike]

I’m just happy as a pig in a puddle that my track all seems to be working and wired up with no apparent glitches (so far)! I wired up 7 busses and about 24 leads around the mainline. I checked and double checked all of it. 3 of the detection sections (blocks) are reverse loops. The biggest problem I’m having with the ARs is learning the procedures for programming the Digitrax PM74s to handle them. I believe DigiTrax is a fine company, and they make good stuff, but they’re very short and not detailed at all on each of their manuals, as to how to accomplish the tasks of programming all these devices

 

[Smudge617]

I’m just happy as a pig in a puddle that my track all seems to be working and wired up with no apparent glitches (so far)! I wired up 7 busses and about 24 leads around the mainline. I checked and double checked all of it. 3 of the detection sections (blocks) are reverse loops. The biggest problem I’m having with the ARs is learning the procedures for programming the Digitrax PM74s to handle them. I believe DigiTrax is a fine company, and they make good stuff, but they’re very short and not detailed at all on each of their manuals, as to how to accomplish the tasks of programming all these devices

I have no experience with the PM74's, so can't comment on that.

I forgot to mention in reply to your earlier post regarding the loco's stuttering as they go round, that can often be caused by dirty track or wheels, and often a combination of both.

Your going to have to clarify this, why do you have 7 buss wires?, you only need 1, with droppers every 4' or as some do, each section of track, 7 seems excessive.

 

[BigGRacing]

That's because your running a DC loco and the power on the track from a DCC throttle is AC, you'll get a hum from the loco's too when stationary, that's because the motor armature is going slightly forwards and backwards at a high rate, which is what that sound is, I wouldn't advise you to have the loco's stationary for any length of time as that can damage the motor, get a decoder in it (even a cheap one like a Laisdcc if you want to run it with a DCC throttle) or disconnect the DCC throttle and use a DC controller if not you may end up having to re motor your loco's.

that was good knowledge for me as well. I was wondering what the hum was and suspected but was not sure.

 

[OgreMike]

I have no experience with the PM74's, so can't comment on that.

I forgot to mention in reply to your earlier post regarding the loco's stuttering as they go round, that can often be caused by dirty track or wheels, and often a combination of both.

Your going to have to clarify this, why do you have 7 buss wires?, you only need 1, with droppers every 4' or as some do, each section of track, 7 seems excessive.

You may be right, Smudge. May have overdone things a bit. But I’m learning about DCC as I go along. It makes the organization a bit easier, I believe. I wanted to have detection sections which would be individually shut down for a short. Each PM74 has 4 circuits to allow for 4 detection sections. They can also show (via LEDs) occupancy and can also transpond for specific occupancy. The PM74 circuits can also be configured for Auto Reverse, and my layout has 4 AR situations . So I ended up getting two of them. One handles the AR sections, the other is wired up for 4 detection sections along the mainline. Overdone? Yes, probably so. But I’m having fun with it, and so far my concept for the wiring and the actual wiring hookups I’ve done appear to be sound. So I’m happy so far.

 

[Smudge617]

You may be right, Smudge. May have overdone things a bit. But I’m learning about DCC as I go along. It makes the organization a bit easier, I believe. I wanted to have detection sections which would be individually shut down for a short. Each PM74 has 4 circuits to allow for 4 detection sections. They can also show (via LEDs) occupancy and can also transpond for specific occupancy. The PM74 circuits can also be configured for Auto Reverse, and my layout has 4 AR situations . So I ended up getting two of them. One handles the AR sections, the other is wired up for 4 detection sections along the mainline. Overdone? Yes, probably so. But I’m having fun with it, and so far my concept for the wiring and the actual wiring hookups I’ve done appear to be sound. So I’m happy so far.

Are your loco's fully analogue or DCC ready ?