DCC Trains vs DC Power Packs. Or more "Rapido vs MRC problems"

[Sumner]

My understand of DCC is that something like 15 volts is needed on the rails in order to end up with 12 volts or so for the motor, after passing through the DCC circuitry. ....

Normally there isn't that much voltage drop.  I run a DCC-EX command station and the drop is more like 1 to 2 volts max and that is a little confusing to read with most meters as the DCC voltage isn't really AC or DC.  To get an accurate reading you need to put the meter in DC and measure between one rail and a ground on the command station and double that.  With my cheap Harbor Freight meter in AC mode I get a little over 10v with a 12v power supply to the command station.

I don't have any problem with running N scale locos with the 12v power supply.  Most of the time at scale speeds the loco is running at way under 12 volts or even 10v.  A bigger consideration in my view is the amperage draw between scales.

Sumner

[$2 Bill]

Thanks for this very detailed write-up, but I still don't know what is the point of this thread.  Since pretty much everything can damage those very delicate and sensitive electronics in a DCC decoder should we just ditch the entire DCC thing and revert to DC powered models?  Or should we just abandon this hobby altogether?

Or should we spend thousands of dollars to buy an AC power conditioner for our layout room and then install anti-static floor or wear ground straps on our wrist while operating and handling out models?

Do your dire warnings also apply to all the smart phones being charged by those USB bricks plugged into household AC outlets?

Yes, there is some sarcasm in my post, but how far do we really take this?

How Far?

For 120/240VAC...
"Full" AC Line Conditioners is maybe over kill but not as expensive at many would think. Some Battery UPS have this feature and even "trips" the UPS On for just being under or over volt on 120/240 input side. Tripp-lite Isobars and some others are "low level" power conditioner, more so the metal box units like Isobar Ultra units. Yes they do cost more then very cheap surge units you get @ amazon etc but made way better. Isobars have been available for Decades and even Hospitals and more use them between an outlet and computer on a "desk." That even when most Desktop and many Laptop PSU have builtin surge protection since 1990's.

More details, NEC "Books" is US Nation and/or Most States Electric Code now Requires Surge/Spike Protection @ the Utility Meter, wired to or in the first "Breaker box." That Code Change covers New and Many Remodel projects.  (Some other counties has or soon will require the same.) Why now many Load Centers have Surge Units Builtin from the factory. For "old work" tight on space, Eaton and others make Surge Protection that fits in 1 full breaker space. (Same space for 240V Breaker for E-Stove, Central AC, etc.) Why? Because nearly everything has some electrics that controls them including Water Heaters, Stoves, and Furnaces wired directly to the breaker box. If you own your home/space Adding this protect everything even if some units protect @ 500-700v. If you lease/rent then often Landlords or Unions limit or fight DIY installing them.

I put a surge bar just to protect a new Gas Water Heater because has electric "brain" because EPA etc "Recently" (about 10 years now) Force the makers to install non-pilot burners and dampers on gas units to stop pilot burn gas 24/7 and stop losing heat up the stack. (CARB or EPA force Bigger water heaters also have Heat pumps too depending where you live.)

For anything on Low Volt side...
You may need to add LV Surge/Spike on AC, DC or DCC because:
Many still uses AC or DC "Accessory Power" from DC or DCC "Bricks" to run things other then trains that many now have electronics. Many have parts tied to or near the tracks could transfer power problems to the tracks.
DC power packs are never made to work with DCC to start with and again have No protection except short circuit to Pass UL and related testing.
Some DCC parts might have protection, others nothing.

That's only for "Normal" Surges etc...
May Seem Funny to some but using Wrist Straps & related tools when handling DCC Engines can protects the Engine and Controller/boosters too. Not wearing them is why many Computers and more die. Oh often home/office computing still has metal cases but even that it not connected to ground or even if it is, user put in/out a video board, etc and zap 1 or more parts that fries now or soon then blame the card or whatever... Important Note: Wrist Straps, foot and work mats, other static safe products have hidden 10M Ohm resistor or other high resistance so is Safe for you and most equipment when powered.

Even if just Operating DCC Controllers in cold weather can cause Zapping the controller or walk around head unit. If doesn't kill something right now can crash the box or anything downstream.

Example: Many Years ago I kept Crashing my PC just sitting down to use it. Why? The metal "desk" had plastic wheels and I Zap the desk often without feeling it then the Desk Zap the Monitor, Keyboard or Mouse to crash the PC sitting on the floor. I had to use Anti-Static spray on the carpet plus put "Wrist strap" wire to "ground" the desk to stop it.

About DCC itself...
Many Controllers and Boosters may soon be abandon as Bluetooth and other Wireless Control on the Engines are getting was easier to fit the space. One company now makes such a system that even has battery option to run without power from the tracks. Right now cost $200-300 per engine setup but can be cheaper "standard" DCC when need the controller, 1 to several boosters, etc.

[peteski]

That sure is more than $2 worth of advice Bill!

[Maletrain]

I think it is going to be quite a wait for N scale "dead rail". 

And, even with Bluetooth getting smaller, there is still the problem that dirty track/wheels can cause drop-outs of the decoder+Bluetooth chip power and annoying restarts - which needs on-board capacitors to avoid.  So, space in N scale locos for at least significant capacitors, if not batteries, is still going to be an issue for adoption of Bluetooth control in place of DCC control.

Also, with high energy density storage devices, we have seen component failures that cause serious fires.  The tantalum "super capacitors" we use in MRR are known for that, as are lithium ion batteries used in our other rechargeable gear.

So, beyond just the space issues for the components, we will need reliability improvements for the high energy density power devices before we can really transition away from DCC in N scale.

[$2 Bill]

My understand of DCC is that something like 15 volts is needed on the rails in order to end up with 12 volts or so for the motor, after passing through the DCC circuitry. I think that is the real reason that is behind the maximum voltage ratings that they use for their circuitry. Other factors come into play with AC, too, like max voltage vs. RMS voltage.

DCC and others often uses H Bridges of whatever type to run the motors. Often 4 MOSFET H bridge tied to main power and maybe ~ 1v voltage drop or less.
But The Electronics... Those need 5, 3.3 or even less volts. So must be Rectified, Filtered and Regulated and that alone can limit or fry from over volts or over current. Quick Example: look up many versions of 7805 5v Regulator.

Old and many New models of DC "bricks" are never made to work with DCC to start with and again have No protection expect short circuit to Pass UL and related testing. "Old school" types and Many Transistor controllers, not just 1300, don't even caps across the rectifiers because DC motors work without them. MANY think can simply add Caps in those or externally but have other problems. IOW If a brick output ~ 16V RMS, Putting a Cap across pushes the volts even higher to the Peak if the Load doesn't such the cap dry between cycles.

[$2 Bill]

Also, with high energy density storage devices, we have seen component failures that cause serious fires.  The tantalum "super capacitors" we use in MRR are known for that, as are lithium ion batteries used in our other rechargeable gear.

So, beyond just the space issues for the components, we will need reliability improvements for the high energy density power devices before we can really transition away from DCC in N scale.

Any Tantalum capacitors has problems just getting Old. Even before any Computer used them... 7400 and other "chips" types had them all over the board to decouple noise and stabilize power. Now in "Retro Computers" the Tantalum can short out or burn along with Rifa, Electrolytic, and other types. And that's ignoring "poison" Electrolytic that are Factory Defective that self destruct only in 1 or 2 years and cost Dell and others Major Money for Warranty Repairs.

Many now claim "LiIon = Fires or worse..." Either pushing BS for many reasons or just echoing same because has no clue because many of those are using LiIon for Decades in Laptops and more. All "Ear Buds" has LiIon too but same people put in their Ears. Yes, it can Burn or Explode but not like all the hype push thru Main Stream Media. Li___ with Iron etc isn't "Safe" either.

Just in Laptops, Dell HP and others use "Premium" cells and major work to charge, discharge, monitor temperature, etc. While Dell etc had a couple of Battery Recalls, number of fires are very low even for the affected part numbers. OEM Ryobi, Makita, etc Battery Tools are same thing and very rarely have problems if not abused by owners or thrown in trash or recycle. (Most Trash and Recycle are Compacted etc causing many things to burn or explode not just LiIon cells.)

In other products say Vapes, "Hoverboards," and most E-bikes, they have problems because how batteries are treated, charged, and more issues even when has "Perfect" cells when made but too often those makers buy the Cheapest Cells that are often "Seconds," "Recycled," etc.

In EV including same E-bikes, big problem is put Hundreds to Thousands of Cell and just 1 cell is made "wrong" or shorted out then others will go thermal runaway too. Add road vibration, impacts in a crash, flooding, and more problems for anything on the roads anywhere...

N Z TT maybe tight on spaces for the batteries anywhere but don't count on wireless in the decoders. In HO/OO the Stay Alive Caps or Batteries are often in a Tender or another car behind a Diesel engine. Often manufactures can get very small battery cells but you can't except via Eflay with iffy cells unless maybe paying more for Digikey and related. But DIY making a battery pack even when have good cells can cause problems.

[$2 Bill]

My personal general rule is to avoid using the "vintage" old metal-cased power packs (like the one pictured in an earlier post). These they tend to have rheostats with a resistance designed around old HO open-frame motors, so they can't provide good low-speed control of smaller N-scale motors. Small old "set" power packs are even cruder and just have taps across the transformer windings, like old Lionel transformers.

"Update:" I've never seen a HO and other power packs that has Transformers with variable tapping like old Lionel. Many of those Lionel with that setup are AC O Trains. (Old AC Lionel use "DC" only to activate the sound effect.)

Yes Many old HO and N "Bricks" does have wire rheostats but If you think only steel case units, sadly often is plastic case ones including MRC Railine 300 that still shows up on Ebay etc. Wire rheostats isn't the "only problem" or even the Main problem dealing with old power packs...

"Update" because this weekend I got another "vintage" HO Power Pack... Likely 1950 to 60's Superior Power Products # 995. Example: https://www.worthpoint.com/worthopedia/vintage-superior-model-995-train-143109746  I got it cheap just to look. Carefully look. And no plans to even test it, forget it to run a train. I worked outside and cleaned my hands after as some of the guts maybe poison/cancerous now and not just because had lead solder.

Inside the "Tanks:"
Big side is a Center Tap Transformer and Rheostat and seems to have a "switch" just have the wiper run off the nichrome at 0 speed.

The Center Tap Transformer means only 2 Rectifiers needed in the Small "Tank" to have Full Wave power. The Rectifiers are Metal not Silicone and Way Bigger to fit inside the "tank" because made "cheap" not like shown in https://en.wikipedia.org/wiki/Metal_rectifier or other places. The metal is ~ 1" Square but almost 1" "thick" for the rest of parts.

No Test? Because many old metal rectifiers are dead to start or soon fry like old Rifa caps and Selenium and related reeks when cooked and are not "safe" to breath the fumes. Also have "Mold" on the wires and Acid attacking the Copper because early PCV insulation have problems. Plus while Pass UL at that time it doesn't have fuse or breakers that I could find. Maybe the "Breaker" is part of the Rectification and part why that's so big. (Model 695 single "Tank" is similar age but maybe Silicone Diodes? Other Companies seem to use same name now so can't find any info for these.)

If you buy these "Antiques"/"vintage" packs from Ebay etc and even they claim "it work," even show a "test," Anything with these problems must be check very carefully or rebuild before use. Even worse if whatever have old Capacitors too.

Side note: The Transistor in "better" power packs in MRC Tech 2 and many more are not Amplifiers just simple "Dimmers" to have 0-100% power. Many DC packs Can't use SCR or Triac as AC Dimmers for lights. (Even when DC have no filtering because often can't reach 0v to reset them for many reasons.) Most but not all PCM units use MOSFET because way low Resistance when Full On, often well < 0.01ohm so don't need a big heatsink. DCC Decoders etc use H bridge with 4 MOSFET for same reason.