DCC power problems

[Acky053]

Hi , I am a complete novice at model railway but trying to get into it in a big way. I have done 3 different track layouts and all worked ok but on my final one when i change any of the outer track to get the train running on the inside track the controller

 

dies on me ,,,,the display goes funny and the train stops . I reset the points and everything is ok. I am using Select unit, have put the little shorts on all the points (removed them still same problem). THe track was running ok but then I added a new set

 

of points and a couple of pieces of extra track and now I have this power problem. I have checked for any possible shorts but it seems the inner track and outer track are at different polarities....how can this be with AC

[poliss]

Have you created a reverse loop as shown here? http://www.brian-lambert.co.uk/Electrical-2.htm#Reversing Loops.

AC still has polarity btw.

[Fishmanoz]

Careful about your use of polarity here poliss as I ended up in an argument about it a while ago. However, I agree with you that polarity is still a useful concept for DCC, a view support by a reference I quoted last time.

 

But if we wanted to be

 

strictly accurate, the AC issue is actually phase. We can have 2 AC signals which have the same voltage and current but are out of phase with each other. If we imagine the sinusoidal voltage waveform that is AC, 2 signals will be out of phase if at the time

 

one is going from positive to negative, the other is doing the opposite and going from negative to positive. If we were to connect these 2 together, we effectively have a short circuit.

 

Then a DCC signal isn't a conventional AC waveform, rather it

 

is a train of pulses, and those pulses are pulse width modulated to carry the DCC signal. Then again, pulses are only a lot sinusoidal signals added together anyway. Ask M Fourier if you don't believe me.

 

Sorry if that is clear as mud to some. I'm

 

actually using some beyond basic maths and electrical engineering concepts in what I have said. But then DCC is a beyond basic electrical engineering concept itself.

[Acky053]

Thanks guys I put another power connector onto the inner loop thinking that the problem was lack of power on the layout but same problem.....I havent wired in the points I am operating them mannually but the problem is the inner loop and outer loop are

 

not working together ....I can't see it being the digital controller it must be somewhere on the track because 2 days ago it was working ,,,,then I put another point in and 4 pieces of track ????

[Flashbang]

Hi

It seems to me that you have a positive rail meeting a negative one somewhere.

Try reversing the two feed wires in one of the loops track power connections.

Otherwise carefully trace around one rail around all the layout - call it 'red rail'

 

and ensure that nowhere can the red rail connect directly to a black rail.

[poliss]

It can only be few things. It could be that you've you've created a short circuit, a connection has come loose, a faulty set of points, loose fishplates, or something else just as simple.

Can you put a photo of your layout on Photobucket and post the

 

link here?

 

[Fishmanoz]

How many power connectors do you have to the track now? Is it 2 or 3?

 

Rather than having made a reversing loop, I think you may have reversed the polarity of your second connector. Try swapping the wires to it and see how you go. If you have 3 connectors,

 

you'll have to get all 3 the same.

[morairamike]

Are both the power clips the ones with NO capacitor fitted? Remove covers and check, if fitted, remove the capacitor. The power clip has the letters A & B stamped on it, ensure that the same terminal on your controller goes to both the As and the other

 

to both Bs. With the power clip in front of you, with the push buttons on your side of the track, B = LEFT and A = RIGHT.

 

1) Leave the wires out of the inner loop connector, fit two point clips to the points. Put wires into the outer power clip. Does

 

all the track inner & outer work NOW?

 

2)Remove the wires from the outer power clip and put them in the inner one, does all the track work NOW?

 

3)If it does, them with the wires connected to BOTH the outer power clip and the inner power clip (with

 

same colour in each connector) i.e. LEFT rail (B) RED, Right rail (B) BLACK, REMOVE THE POINT CLIPS, apply power and it should all still work.

 

If it doesn't, then are you using ELCTRO or INSUL frog points? The above should work with INSUL but will not

 

with ELECTO due to frog being both effectively RED (A) (+) AND BLACK (B)(-)(unless you use isolating rail joints). Note Hornby do not make ELECTRO FROG points.