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On page 206 of the DCS Companion, Barry talks about repurposing a DCS Remote Commander (DCSRC) to be a watchdog signal generator.  I am building a new layout utilizing a TIU and would like to dedicate a siding as a programming track, so that adding an engine will not interfere with engines already running on the track.

I am not clear on the description in the book about how to properly make that happen.

My intention is to isolate the siding using a toggle switch and have the RC generate the watchdog signal when power is switched on to the siding.  The book says to parallel the DCSRC with a wire pair from the TIU or Terminal Strip.  At that point I believe the DCSRC would generate the watchdog signal but subsequent programming would be thru the TIU.  

(1) is power brought to the DCSRC or is it just powered by the batteries (I would guess this a passive mode if true?)

(2) what causes the DCSRC to generate the watchdog signal?   Will it do that in response to seeing the track power on its outputs that is switched on from the TIU?

(3) can it remain active the entire time the siding is active, or does it need to be turned off after performing its function?

(4) when connected in parallel with the TIU, will the watchdog signal be broadcast over the entire layout?  If so, is that OK?

All suggestions, including better solutions, will be happily accepted!

Thanks in advance for your assistance .... Joe

 

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I have done exactly what your describing.  Connect the DCSRC to your track passively.  When you toggle power on to the siding track you will generate the watchdog. Keep in mind this is only needed when grabbing power from a mainline already powered up with a TIU channel.   Why not just use a separate TIU channel for your programming track?  If having an isolated programming track is your goal I think utilizing a separate TIU channel would work better.  

(1) is power brought to the DCSRC or is it just powered by the batteries (I would guess this a passive mode if true?)

It is powered passively just by being connected to the track. When track power is toggle-switched on, the DCSRC powers up and generates a watchdog signal.

(2) what causes the DCSRC to generate the watchdog signal?   Will it do that in response to seeing the track power on its outputs that is switched on from the TIU?

It generates the watchdog signal every time it initially receives power (from the track), as if its was a TIU channel.

(3) can it remain active the entire time the siding is active, or does it need to be turned off after performing its function?

It just stays on whenever the track has power, and turns off when track power is turned off.

(4) when connected in parallel with the TIU, will the watchdog signal be broadcast over the entire layout?  If so, is that OK?

Yes, it will and that's fine. Nothing bad will happen. In fact, you could then run trains using Bothe the DCSRC handheld remote at the same time as running other trains with the DCS Remote.

Clem, the thread I referenced has all the design files to order the PCB from OSHPark and the parts list of cheap parts.  Since it's all thru-hole stuff, it's easy to assemble, and then you too will have a perpetual watchdog.

I just checked, and I have one of the kits I was offering remaining, send me an email and I can fix you up.  It contains all the parts needed to upgrade one DCS-RC box.

I have never had a problem with an engine missing the TIU's WD signal at system start up so I don't think the length of time is a factor. As for the actual length of time the TIU's WD signal lasts, others here could explain this better than I can, that is, if you are interested. 

The repeating WD signal is so you can power up a siding/spur/yard track etc. at anytime and the parked engine(s) will get a WD signal and do what they are supposed to. Otherwise the WD signal is sent only once when the TIU is powered up. Powering a siding connected to an already powered track won't give you a WD signal. 

I also have one of the devices for the DCS-RC that GRJ and Stan were kind enough to develop and they work great to eliminate this problem. This a a really cool device!

Last edited by rtr12

To refresh everyone's memory, this is the original board installed, this one is the same size. 

For the new version the pot faces out between the silver crystal can and the larger IC on the left.  If there's room on top, you could just mount the LED on the circuit side facing up, but I'm sure it'll be quite visible facing down as well if there isn't room.

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JK PHOTO, I too would like to do this watch dog signal generator project for all my toggled sidings. For now though, so that my engines remain dark and silent when power is toggled to a siding, I do these steps:

1. Lock the engine in conventional neutral (this is a good practice anyway if you never run in conventional cause it prevents run-away's).

2. Turn off the smoke and sound with the switches or pots on the engine.

3. When finished running the engine and parking it in the siding, shut off the lights before shutting it down.

Now the next time you go to run the engine and toggle the siding, it will be dark and silent without having to see a watch dog signal. And if you accidentally toggle twice, the engine won't take off at full speed. Next find the engine in your remote and start it up, then turn on the lights, just like a real engineer would do.

Pro's and Con's:

Pro. This one is personal. I've become annoyed over the years with that same "steam generator turbine whine" sound, on every MTH steamer when they start up. This "watch dog signal work around" eliminates that sound because it was already performed when the track power was applied and no volume to broadcast it.

Con. If you do want to hear the start-up sounds (especially if your like me and love the diesel start-up sounds) you have to remember to hit the shut-down button first, then the start-up button, if you want to hear those sounds.

This has been working for me until I get around to doing this project.  

The variability of the cap value and the IC trigger point makes the spread too wide to simply pick a set of components.  We had to calibrate them with a resistor selection, the pot just eliminates the need to test resistors before soldering them in.

Obviously, it could have been done with a 555, but as Stan pointed out, that would have run the current consumption up quite a bit.  Although there are doubtless tons of other ways to do this, this is the way we have.

Peeling the layer of the onion a bit.  There is actually a relatively small timing window around 1 sec or so where this scheme works. 

On the short end, you can't reset too quickly because measurements showed the DCSRC itself takes about 3/4 sec before it generates its watchdog.  Hence if the reset it faster than every 3/4 sec, you'd never get a watchdog at all!

On the long end, you can't reset too slowly because a DCS engine will decide to startup in conventional if it does not see that watchdog in a timely manner.  I can't recall the number but if you turn on a DCS engine in conventional, that decision window is pretty short.  In other words you hear the engine sounds start up in a couple seconds at most if there's no DCS.

So in such an environment where there are no MTH-provided specifications, a self-imposed timing requirement was determined.  This also eliminates any unit-to-unit variability as a suspect when troubleshooting on OGR.

OK understood. The first one I installed must have been a lucky shot as it seems to fire just about right on every second or so, and works exactly as intended in my TT yard. Hopefully the next one will work similarly. One other thing, can you retrofit the pot and LED to an original release PCB, or the PCB's different?

Rod

Last edited by Rod Stewart
Rod Stewart posted:

...One other thing, can you retrofit the pot and LED to an original release PCB, or the PCB's different?

As I understand it, GRJ is designing a different PCB.  The new PCB adds space for a pot to adjust the "timing" rather that iteratively inserting different fixed-value resistor to "tune" the timing.  If you have an original PCB, I suppose you could mount the pot somewhere on the board and tack-in some short wires to add adjustment capability.

But if you have a working unit right now that blinks in the specified window, you should never need to re-tune it.

Yep, it's a new PCB.  I ordered some of them, and I'll post the design files and BOM here for anyone to order as they see fit.  Pretty hard to see how it could fail, I just replaced the 1M (nominal) resistor with a 750k and a 1M pot.  My experience was that I needed more than 1M, usually about 1.2m-1.3M, so I slanted the values that way.  The LED was just a frill that used one of the extra buffer sections, a resistor, and the LED.  I posted the new schematic a couple posts ago.

JK Photo posted:

 I am building a new layout utilizing a TIU and would like to dedicate a siding as a programming track, so that adding an engine will not interfere  

I setup this with a Z1000 powering a section of track and the DCSRC powered in passive mode. Initially I inferred that this setup would be sufficient for configuring a dedicated programming track. Is it correct that in addition to the DCSRC setup as passive, you must also connect to a TIU channel for this to work?

Tom,

Is it correct that in addition to the DCSRC setup as passive, you must also connect to a TIU channel for this to work?

The DCSRC can only operate DCS engines that are factory-new or reset to Factory Settings. If you want to simultaneously operate multiple DCS engines independently of each other, you need to have a TIU channel connected to the track.


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