DCC wiring (best practice and point clips)

[JamesRoc]

DCC novice here!

I've recently purchased the Hornby Elite which came with only one track power connection wire.

My layout is essentially three loops interconnected by various sidings.

What's the best way to wire the entire layout including the other two loops as the Elite has only one track power output?

Many thanks,

James

Mod note - title amended to include additional discussion.

[P-Henny]

Assuming a Hornby 00 track layout. Then the simplest option is to fit Hornby R8232 DCC Point Clips to all your points. The R8232 clips circumvent the electrical isolation built into Hornby points and makes the WHOLE layout track always live for DCC. The R8232 clips will extend your Elite output power through all your loops and sidings via the point connection routes.

Make sure that you are also using either a DCC Digital R8241 or R8242 track power connector and NOT the Analogue R602 or R8206 versions (including R8201 link wires). Using the Analogue power connectors can corrupt DCC signals.

If your layout was previously Analogue and you are updating it to DCC, then you are almost certainly currently using Analogue track power connectors that need to be updated to Digital.

If you are not using Hornby 00 track, then tell us which track you are using and an alternative suitable solution can be offered.

You might benefit from reading Chapter 6 in the 'Getting Started........' sticky thread at the very top of the 'General Discussion' forum.

[JamesRoc]

Many thanks for the helpful information Paul.

I've ordered the above as you recommended.

Yes it's an 00 gauge DC track layout the vast majority of which is Hornby track and points but I do have some Peco track and points on the layout.

Will the point clips above function the same on the Peco points? I presume every set of points on the layout will need the point clips?

Kind regards,

James

[P-Henny]

Yes, each and every point needs some form of electrical bypass, whether that be clips or a BUS (see further below).

If the PECO points are from PECOs ST range, then the Hornby R8232 point clips should fit.

Although using point clips is the simplest DCC update solution. Many DCC layouts implement a DCC BUS for power distribution.

A BUS consists of a pair of wires run under the baseboard following the rough plan of the layout. These wires are typically 32/0.2mm wires loosely twisted together and connected directly to the Elite Track A & B DCC output. At the other end of the twisted wire BUS, it is optional but IMO advisable to fit a snubber. A snubber is made up of a 0.1uF Ceramic capacitor rated at 50 volts or higher in series with a 100 Ohm resistor rated at 1 Watt (2W preferred). The series resistor & capacitor is then installed across the two unterminated wires of the BUS wires. A snubber prevents DCC voltage spikes from damaging decoders and IMO dramatically improves long term reliability.

Then in a number of strategic locations (minimum each side of a point) a small amount of insulation is sliced off the BUS wires to bare some wire and Droppers are soldered to the BUS and the other Dropper end soldered to the track (underside if laying new track or outside of rail if track is already laid).

The Droppers are typically 7/0.2mm wire. Some layout builders (me included) go overboard and fit droppers to each and every track piece so that the track joiners are relegated to just performing track alignment and fixing together and are therefore not relied on for the transference of electrical power.

Obviously with a BUS solution, soldering is required, so this relies on your skill set and capability. There is a FAQ tutorial for 'How to Solder' in the 'General Discussion FAQ Index' sticky thread.

As your layout was previously DC, don't forget my original reply comment about Analogue vs Digital power tracks. If you do decide to implement a BUS then any plug in R602 track power connectors should be removed (this includes R8201 link wires if used). Any R8206 power tracks can be modified for DCC Digital by flipping open the cover between the track rails and snipping out the component that you will find soldered across the two rail connectors. In a BUS solution the modified R8206 track piece can be left in-situ but unused.

[Brew Man]

In addition to Paul's advice I can confirm that the points clips will work on Peco Set track, (ST) range and their Streamline, (SL) Insulfrog range. I had all of my Peco points fitted with clips before using droppers from a DCC bus.

[JamesRoc]

Many thanks Paul for the detailed info, and thank you Brew Man.

Yes as well as the point clips I’ve ordered both the Digital R8241and R8242 track power connectors, one for the programming track.

I’ll keep it simple for the moment until my knowledge increases.

Kind regards,

James

[P-Henny]

Something I forgot to include in my previous replies. Since the track is not new purchase. Make sure that the R8232 DCC point clip contact area on the side of the rails where the clips fit is spotlessly clean. Any dirt and grime will increase resistance. This (resistance) has been known in some instances to generate heat and enough heat to melt the plastic in the points. Some clips have been observed in severe cases to glow red hot.

The easiest way to clean the inside of the rails is with a glass fibre pen (see link). Wear eye protection as the cleaning process can generate glass fibre dust. Use a pen only on the contact area on the side of the rail, not the top rail surface.

glass fibre pen for sale | eBay

[Fishmanoz]

One addition on your existing DC power tracks or clips - it is easy to convert them for DCC operation rather than replacing them. Just flip open the black cover between the rails and snip out the capacitor you find there.

[Barry-350851]

The "best practise" way is to use cables going around under the baseboard with smaller wires going up to every single piece of track and everything being soldered (small wires soldered to the track and to the bus cables.

On a large railway, say going around a large loft or garage where the track is weathered and ballasted then this is really the only reliable way. glue and paint gets in the track joins and the large number of them breaks the power and degrades the signal. So you really need that separate cabling to supply the power and DCC signals.

For a Trakmat sized layout with no track weathering or ballasting then a single power source and point clips is probably OK.

What works for you will depend what you have and intend to do long term. A medium layout with 3 loops and sidings where you aren't going to paint or ballast the track I would say that the under-baseboard cabling (bus) with the droppers to each section (not each piece) of track should be enough.

There are lots of solutions to connecting bus cables together and connecting droppers to the bus without soldering. Rail joiners with droppers pre-soldered to the bottom exist.

[Fishmanoz]

James, Paul and Barry have told you pretty much the same thing here, and comprehensively. But let me add just a little:

• over the years, a number have reported long-term reliability using only a single connection and DCC point clips, even on a 3-loop layout. If it doesn’t work for you, you can install a bus down the track
• learn to solder if you don’t already know. There is a tutorial in the stickies at the top of the General forum
• joiners with pre-soldered droppers - definitely not best practice. Joiners are the potential long-term problem as they get loose and tarnish and become high resistance. Much better to solder to the track.

[Daedalus]

" Any dirt and grime will increase resistance. This (resistance) has been known in some instances to generate heat and enough heat to melt the plastic in the points. Some clips have been observed in severe cases to glow red hot."

that is totally impossible!

[Fishmanoz]

Red hot, yes quite unlikely.

Melted points another matter. At least a couple of instances documented here. Ask Yelrow.

Edit - see Paul’s link.

[Barry-350851]

James, Paul and Barry have told you pretty much the same thing here, and comprehensively. But let me add just a little:

small change - delete Barry’s “best” and insert best practice

over the years, a number have reported long-term reliability using only a single connection and DCC point clips, even on a 3-loop layout. If it doesn’t work for you, you can install a bus down the track

learn to solder if you don’t already know. There is a tutorial in the stickies at the top of the General forum

joiners with pre-soldered droppers - definitely not best practice. Joiners are the potential long-term problem as they get loose and tarnish and become high resistance. Much better to solder to the track.

 

 

On the point of a later addition of a bus, note that adding droppers by soldering becomes near impossible once track has been ballasted. It doesn't sound like the OP is planning to ballast or paint the track but other readers might.

 

 

I absolutely agree that soldering is the best way, I think I made that clear. However, in the interest of giving people the information to make the choice, my opinion is that any connection method other than soldering is going to rely on rail joiners and of the available non-solder connection methods, joiners with droppers are more discrete than numerous R8242 scattered about.

[P-Henny]

" Any dirt and grime will increase resistance. This (resistance) has been known in some instances to generate heat and enough heat to melt the plastic in the points. Some clips have been observed in severe cases to glow red hot."

that is totally impossible!

 

 

@Daedalus

Before you poo-poo somebody's response, research it. The comment came from reading posts on this forum. The thread below was the easiest to find because of its title, but this is not the only instance of the issue being reported, and yes there was one post I recall of clips on a larger layout that were nearest to the power connection** being red hot, because the whole layout power was going through them. So the forum evidence of point plastic melting shows that it is not impossible.

Melting POINTS :: Hornby Hobbies

Note** In this instance the forum member connected his power connection to a siding so the whole layout track power had to go through that siding's point clips.

Passing a current through a resistance will generate heat. This is fundamental physics of Ohms Law [ Watts = I²R ].

[Daedalus]

But increasing resistance reduces current. I do not know what is going on but you can not increase current by having a bad connection.

[morairamike]

A bad connection increases resistance that resistance causes a voltage drop and heat is generated across the resistance.

[Carbone]

It also causes a decrease in current so the work done remains the same.

Voltage is defined in terms of energy and current.

SI Unit of Voltage

• Volt can be expressed as the potential difference between two points in an electric circuit that imparts one joule (J) of energy per coulomb © of charge that passes through the circuit.

[P-Henny]

POSTSCRIPT.

Ironically today (a few days after the posts above). Another forum member reported his DCC point clips glowing red hot and point plastic melting. See linked post below. My previous comments on this issue have now been vindicated.

https://uk.hornby.com/community/forum/track-turnout-clip-overheat-355939?ccm_paging_p=1

[96RAF]

My standard test for loose (high resistance joint) fishplates is to power the track and run a thumb across each joint. The loose ones are invariably hot and easily found.

Those springy steel point clips are not the best material for conductivity.

[Barry-350851]

POSTSCRIPT.

Ironically today (a few days after the posts above). Another forum member reported his DCC point clips glowing red hot and point plastic melting. See linked post below. My previous comments on this issue have now been vindicated.

https://uk.hornby.com/community/forum/track-turnout-clip-overheat-355939?ccm_paging_p=1

 

 

To be honest, while not questioning the possibility, I was struggling to see how this would happen. A short would usually trip the controller and most people would struggle to have enough stock running at once to demand the current to create the heat.

I'm guessing in these cases there has been some kind of short but enough resistance in the circuit to prevent the controller from tripping. I hadn't considered that as a possibility.

[Howbi]

@Barry-350851 It has nothing to do with a short circuit, if the point clip is not making a perfect connection with the side of the rail then arcing will occur which generates heat, as the current demand increases from the layout so will the heat leading to melting of sleepers as described on many occasions on this Forum over the past 12 years in my experience. I also have experienced a heated point clip where my only feed to the track was via a siding then through the one point clip.

[P-Henny]

....and most people would struggle to have enough stock running at once to demand the current to create the heat.

 

 

Barry, it does not take a lot of current to generate heat. Say you have a 4 Amp PSU feeding 1.2 Amps into a layout (say four running locos with sound plus lit carriages) and all that current is passing through one single point clip.

Now say that due to either tarnish (oxidation), corrosion or just a poor connection there is a very modest 8 ohms of resistance between the clip and the contact area on the rail.

8 ohms is a small enough value to not significantly affect the operation of the layout. But, the cross sectional area of the contact area with the 8 ohms resistance is very small.

Ohms Law calculates that Watts = Current Squared x Resistance so the Watts = 1.2 x 1.2 x 8 = 11.5 Watts. This is a lot of potential heat to dissipate in such a small area of contact, enough to burn one's finger if touched.

Even with smaller current values the Wattage is still relatively high. For example 800mA = 0.8 x 0.8 x 8 = 5.1 Watts and still enough to burn one's finger if all dissipated in a very small spot location.

My layout has a snubber with a 2Watt resistor dissipating less than 1W of power. It runs very warm to the touch, not enough to burn, but enough to be uncomfortable to touch for any length of time. Thus the dissipated Watts does not need to be significantly high to give the reported plastic melting observations members have made.

[96RAF]

Hornby PSUs tend to work on a constant power basis… i.e. as the load increases above the rated power level, the voltage drops and the current increases thus maintaining constant power.

The 4-amp unit is rated at 60W but can deliver up to 80W under overload conditions. Bench tests have shown that self protection starts at 4.5A (14.5V) and shuts down at 8A (7.5v) into pulse mode. Similar for the lesser capacity wall wart PSUs.

At risk of repeating myself springy steel clips make a better heating element than a conductor, hence the less current they carry the better.

 

[Barry-350851]

My layout has a snubber with a 2Watt resistor dissipating less than 1W of power. It runs very warm to the touch, not enough to burn, but enough to be uncomfortable to touch for any length of time. Thus the dissipated Watts does not need to be significantly high to give the reported plastic melting observations members have made.

 

 

Sorry, I was specifically referring to the rare occasions of the clips glowing red which would mean they were getting on to 500 deg C. Instantly burning fingers starts at about 80 deg C. I don't know exactly what temperature sleepers will melt at but it'll be closer to fingers than to glowing metal.

The poster you linked to was "only running a couple of locos" at the time. Getting hot enough to melt sleeper chairs would seem feasible but to glow red hot I think is more probable to be a short.

There doesn't appear to be any warning about this on Hornby's product page.

[96RAF]

There doesn't appear to be any warning about this on Hornby's product page.

The very first review on the product page tells of this problem. The ‘i’ pop out warns against sharp edges and kids, etc but not current carrying hazard.