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Decoder Stalling

1) STALLING PROBLEMS
2) SOLVING TOUGH PROBLEMS / NON LAYOUT OWNERS
3) FOCUS ON CAPACITOR BASED SOLUTION
4) TWO TYPES OF CAPACITOR SYSTEMS.
5) INSTALLATION


1) STALLING PROBLEMS
Decoder that do not run reliably at slow speeds around the layout often suffer from multiple problems.  This is especially true of engine with short wheel base or offset wheel pickup.  The common problem being few wheels are being used for electrical pickup from the track.  Such engines can have problem IF any one of the following is true.

COMMON PROBLEMS

A) Poor track/rail power due to intermittent or lost electrical rail continuity.  Mechanically loose rail joiners have failed electrically and/or the track feeder is broken.

B) Dirty Track

C) Dirty Wheels.

D) Turnouts.  Dead point rail or frogs.

Fortunately that above common problems can be fixed by the layout owner.  For solving Turnout Problems go here:
Wiring_for_DCC: switches


2) SOLVING TOUGH PROBLEMS / NON LAYOUT OWNERS

For the person who cannot control the quality of maintenance of the layout itself or do not own the layout, the only choices left are to focus on the engine itself.  The solution is to somehow find a way to keep the motor moving through the dead spots.  There are 3 possible solutions

1) Add rail power pickups to the engine.  This requires modification of the engine by adding rail contract wipers to make up for the limited electrical wheel pickup.  The success of this option of course depends on the skill set of the engine owner and the time he/she is willing to spend on it.

2) Add or improve the flywheels on the motor.  Flywheel are mechanical energy storing devices that keep the motor moving but does nothing to keep anything electrical alive.   This is an easier solution given there are lot of parts available to do it with.   However typically there is no space to add a flywheel to the engine without major modification.

3) Add supplemental capacitors to the decoder.   Capacitors are electrical energy storing devices that keep everything alive including the motor.


3) FOCUS ON CAPACITOR BASED SOLUTION

Of the above, #3 has become very popular option including support for it from DCC decoder manufactures.  HOWEVER, the idea of simply just adding capacitors WITHOUT the required “high current inrush" control circuit can result in your DCC system boosters having problems reliably operating. 

The chances of seeing the problem depends on

a) How many sound decoder engines you have on the layout.
b) How many engines you added capacitance to are on the layout.
c) The value of capacitance you added per engine.
d) The current rating of your booster inside you DCC system.

On small layout this is typically not a problem.  But for large layouts this is a known problem that early DCC users first experience when sound decoder engines started appearing on layouts in mass.  Why?  Sound decoders introduce the need for bigger capacitors just to keep the sound system portion of the decoder alive on common every day poor track pickup issue.  They did not include any inrush current control because the capacitors being used were relatively small compared to what is being discussed here.  But on large layout, the collective capacitance value of all the sound decoders together becomes very large value.  Here we are talking about ADDING SERIOUSLY LARGE AMOUNTS OF CAPACITANCE ON A SINGLE LOCOMOTIVE.  My point is you must have a high current inrush circuit involved in the capacitor solution if you going to have any chance of avoiding problem.


4) TWO TYPES OF CAPACITOR SYSTEMS

There are two type of capacitor circuits used with DCC decoders.

1) "Keep Alive”  People simply call this KA for short.  KA’s are super capacitors circuits made by multiple DCC manufactures that have the required built in “high current inrush" control circuits.  Most of them you connect just two wires provided.  (TCS has a trademark on the term Keep Alive.)

2) "Stay Alives”.  Stay Alives are custom hand built (DIY) devices using common capacitor circuits for decoders.  They MUST include the required “high current inrush" control circuit.   When completed, the final connections are done with two wires.

KA’s are smaller, run a locomotive far longer and easier to install than Stay Alives.  The BIG disadvantage of KA’s is cost.  You get what you pay for.

To learn more about the technical difference, go here:
Keep Alive Compatibility


5) INSTALLATION

Marcus Ammann has a great website that help people put these capacitive solutions into a given decoder.

For Those that are installing Keep Alive or KA go here.   This website PRESUMES you are using KA's which is why you do NOT see the “high current inrush” circuit anymore. 
Keep Alive Website

For those who are working with Stay Alives, which REQUIRE schematic for the “high current inrush" control circuit, go here. 
Stay Alive Website

Unfortunately Marcus’s website use the two terms “Stay Alive” and “Keep Alive” interchangeably which is why there is confusion and/or important information content lost. 

11/13/15