test track not same as program track?

Model Railroader General Discussion (Model Railroader)
1

Hello everybody

I just bought an MRC sound decoder and was reading the paperwork and MRC recomends testing out a new decoder install on a test track that is build with a 27 ohm resister to limit current, they state that the program track is not equal to a test track[D)].

does any one else out there have a test track?

should I put one in?

bill

2

The reason for the resistor in the program track is so you dont ‘fry’ the decoder. Here is my take on it:

I dont have a resistor on my program/test track. I inspect the DCC installation before I place it on the track. You just need to make sure the motor is isolated from the frame and make sure this situation wont happen when you put the shell back on. But that is just me.

David

3

Some decoders need a booster to get programming to them…or, put another way, some DCC systems don’t put out enough power in their programming circuit for Paged Mode. So, if you have that booster, and want merely to test a decoder, it would seem to me that you might be inviting disaster in the event that the wiring didn’t quite get done properly…as in, there is a short.

So, if I understand the difference correctly, a test track is merely powered with just enough voltage to get the decoder to wake up and perform some functions to let you know it is happy with the wiring job. Too much power, as on some programming circuits, when the decoder is bad or iffy, could spell disaster.

I will keep an eye on this thread in case I need to adjust my thinking.

4

No they are not the same.

Actually, I believe with the MRC, the programming track will only allow you to program the decoder, it does not have enough power to run anything. A test track on the other hand will allow you to program and run the loco, in a very reduced capacity and only for a short time, as the resistor heats up quickly. You can also read the CV values on the programming track. This is useful, should, heaven forbid, you didn’t write down the values because you know you’ll never forget them and…you forget them cause you have dozens of locos. (You understand of course I’m not talking about me…[:-^])

When I got the original Prodigy, it came with a resistor and instructions for wiring a test track. I built the test track and programmed and tested my decoders on it. When I upgraded to the PA, it did not come with a resistor but did have seperate outputs for a program track. I converted the test track to a program track and use it, on occasion, to program stubborn decoders or reset decoders that have lost their minds. In fact, after installing quite a few of various manufacturers decoders, I check the wiring carefully, before I put them on the track, and haven’t fried one, thus limiting the need for a test track.

You’ll need a program track. If you are New to DCC, you might want to set up a test track until you are comfortable with your decoder installtion skills.

Good Luck and Enjoy.

Tilden

5

Depends on if and what you want to test. My test track is a loop so I can let the thing run a bit.

6

Might be a bit of overkill, but then since the MRC sound decoders don;t officially support CV readback it’s tough to test them in the usual way - which would be to simply place the loco on the program track (which IS current limited) and verify that you can program and read CV values. If there is a short in your wiring, it won’t work on the program track, but the low current will prevent the decoder from being destroyed. Placing the loco on the main track with full power, even from a smaller 2.5 or 3.5 amp system, would likely fry the decode if there was a wiring error, although some brands of decoders do have protection from shorts or lack of proper motor isolation.

That 27 ohm resistor had better be a 10 watt type. At 14 volts to the track, assuming a decoder fault that is a dead short, that’s still over .5 amps flowing, possibly enough to damage the decoder anyway, although not instantly so you would probably be able to shut things off in time. And ,5 amps flowing through a 27 ohm resistor is 6.75 watts.

–Randy

7

Do not confuse a 'test track’with a ‘programming track’. These can be 2 different animals:

  • A ‘test track’ is a short stretch of trackage you can ‘run’ an engine on. In a DCC enviroment, this is hooked up to my main track power bus(it’s some Bachmann EZ Track that is about 8’ long).
  • The ‘programming track’ is hooked up to my Digitrax Chief ‘programming’ leads and is another section of Bachmann EZ Track. I cannot ‘run’ anything on it, just ‘program’ the decoders in the engine that is sitting on it. None of the programming commands that are ‘broadcast’ to the ‘programming track’ get to the mainline or the ‘test track’.

Now, most DCC programming commands are ‘on the main’ type, but setting the locomotive address is a special animal(unless your decoders have a ‘lock’ feature). You do not want all of the engines on the layout re-programmed by mistake!

The note about putting a resistor in parallel with the programming track is to make the total current flow greater. I have never had to use this trick or the ‘programming booster’ to get my QSI Sound engines(BLI/P2K) to program.

Jim Bernier

8

OK let me see if I got this straight, My DCC system is the MRC prodigy advance 2, and I have a program track set up.

Can’t I just test a new Sound decoder on the program track I mean if you can read and set the CV’s then would’nt that indicate that the decoder is wired correctly, or will a short circuit not effect programing?

in any case I don’t think I am going to install a test track, esp. if the decoder may fry anyway I guess I will just have to make sure I install it right.

thanks for the help everyone

bill