Dropping Battery Power, But Going With DCC Wireless

Hi Hal,

Glad you are joining the world of DCC.  Here’s one thing (or two if you have the room inside the loco shell) I think you should add to your locomotive – a Keep Alive capacitor.  This allows your loco to run seamlessly over dirty track by drawing from stored energy in the capacitor when power to the loco is interrupted.  You may never need to clean your track again since running your train will act as a track cleaner on its own.  These are just basically a series small super capacitors (hence the high cost) that store up energy in a very small package (usually takes about 2-minutes to charge them fully via DCC power on the rails).  The more you add, the longer the stretch of “interrupted track power” for which you can run over.  These are especially nice for short wheelbase locos such as your switcher but I would also recommend them for longer wheelbase loco as well, such as the Atlas dual motor locomotives.  Just note that the dual locomotives require that much more power to keep running but usually two (2) KA2 Keep Alives in parallel should be enough for a dual motor O scale loco to give several seconds of runtime after power is removed.   The only caveat is that you need to locate the (+) and (-) locations at the bridge rectifier for the decoder you plan to add them to.

http://www.traintekllc.com/TCS...roductinfo/TCS-1456/

http://www.traintekllc.com/TCS...roductinfo/TCS-1454/

Here’s an example demonstration video of TCS sound decoder with a Keep Alive built in but the effect is the same when adding a Keep Alive add-on to your locomotive.

http://youtu.be/wR16ROCEFjw

Scott K.

Austin, TX

HEY SCOTT,

Thanks for that info!

Woudn't the same effect be gained by bridging the capacitor across the motor terminals? 

This way it would continue to supply energy to the motors during the brief millisecond periods when track power is interrupted.

BAD ORDER HAL

Hi Hal,

Putting one of these Keep Alives across the motor terminals will basically do nothing since the motor would continue to suck all the stored current out of the capacitor until it is empty.  In addition, since these Keep Alive devices have a resistor (say 100 ohms, but it may vary in value due to the capacitors used) built into the positive input lead to limit the capacitor inrush charge current.  That is why these Keep Alives take several minutes to charge up – if the resistor was not there, then they would charge up instantaneously but… then you would keep blowing the circuit breaker while in decoder programming mode due to the high inrush current once you put the DCC system in programming mode.  Without the surge resistor installed, at time = 0 the inrush current to charge up the capacitor would almost be infinite and appear to the DCC system as a short circuit until some time passes and the capacitor charges allowing the inrush current to decrease.  DCC decoder programming mode allows for two-way communication between the decoder and the command station but is done at very, very low current levels to protect the DCC decoder electronics.  Note that even with this surge resistor in place on the Keep Alive device, some DCC systems still need an additional programming mode booster to overcome the remaining (albeit reduced) inrush current that is still present with these capacitors since the DCC system programming mode circuit breaker is so fast acting and set at a very low current value.  Not having inlet surge resistor in place may even trip the main booster circuit breaker while in regular run mode.  

A second reason this will not work is because the resistor on the Keep Alive device’s inlet side would also cause any re-supply current for the capacitor to take the path of least resistance  and go directly to the low resistance motor (say 7 ohms).   Therefore, the keep alive capacitor will never be recharged if the capacitor was hooked up directly to the motor leads.  By placing the Keep Alive capacitor device at the decoder *DC* inlet. e.g. after the decoder bridge rectifier – which changes the AC (or bi-polar DC) DCC signal on the rails to full wave DC to operate the electronics on the decoder it can always have a constant supply of DCC current from the rails (which are always live at full voltage in DCC) to recharge the capacitor between power interruptions.  When the decoder experiences a power interruption, e.g. due to unpowered frog or dirty track, then the capacitor can quickly discharge its stored energy through a one way diode on the Keep Alive circuit board that bypasses the surge limiting resistor mentioned above and supply its stored current to the decoder DC input to, of all things,… keep the decoder “alive”.

The reasons mentioned above are why a Keep Alive device will not work with analog DC operation.  You have to have an intermediary device blocking the discharge of the capacitor when not needed (in this case it is the onboard DCC decoder) and only have the capacitor supply current when needed.  Just another reason to dump analog DC and go DCC…

Scott K.

Austin, TX

THAT'S RIGHT, SCOTT!

An uncharged capacitor has zero surge impedance at zero time, which is why a series resistor is employed, to provide a finite time-constant, otherwise a capacitor of ONE FARAD would be required to satisfy a 7-ohm elelctric motor!

Anyway, I'll probably retrofit a keep-alive cap in short order.

BAD ORDER  (Here's the TX and RX I'll be picking up on Sunday: These components will be added to my existing DCC system to make it Wireless.)

Hal,

I'm just curious and in no way am I trying to be wise guy or anything like that. You have simple layout. No switches. I had a layout like that once. Just how often do you "walk as much as 36 feet to the farthest point on my layout to correct something"? When I had a simple oval (much like yours only smaller) I had Atlas track with mostly RTR rolling stock. I don't recall ever having a single derailment. I would image your layout being similar to that only larger. Like I said I'm just curious.

I'm not trying to talk you out of DCC either. I love DCC. I much prefer it over analog DC.

I operate a fairly large railroad with 7 wireless NCE cabs.  It's proven to be highly reliable and easy to use.  In a multi train environment I find DCC has significant operations and wiring advantages over DC cab/block control.  But for single train operations wireless DC control may still be worth consideration - if you haven't already invested in DCC equipped locomotives.  There is a wireless DC alternative used by G scalers that works for O scale as well.  Before adopting DCC for my new railroad, I used 4 Aristo wireless DCC cabs to operate a walk around DC railroad that had previously been wired for block/cab control.   It was relatively inexpensive and worked well.

Ed Rappe

HEY HUDSON,

Derailments?   NEVAH!   With 43" to 48" curves and short 2-axle trucks, this doesn't happen with either my switcher or my road engine.

My reason for dashing between my control station and the track is: 

Start.....Stall.....Start.....Stall.

Every time this happens, I have to clean the track in that area with alcohol-wetted cotton balls, then run back to the control station to give it throttle again, bumping my thigh on the corner of the pool table every time!

Then I give the GP-35 throttle...it goes 2 inches, then stalls again, with the lights going out too. I have to do this as many as 5 times before it begins to run steadily!

This is frustrating, Hudson! 

BUT NONE OF THIS HAPPENS WITH MY SW-9 SWITCHER! 

Maybe my GP-35 has dirty wheels, which could be why it stalls even on clean track. 

I don't know, and I also don't know how to clean the wheels on these engines!

BUT THIS WILL ALL BE OVER ON SUNDAY, because that's when I'll pick up my Wireless Conversion Set to add to my MRC DCC System...then I won't have to run anywhere, because my Control Station will always be in my hand!

SEE? 

Bad Order

SCOTT,

It's still not clear in my mind...maybe it's because it's been almost 16 years since I recieved a paycheck from an Aerospace firm as an Electronic Engineering Technician!

What still confuses me, is how can putting a capacitor across the output of a bridge rectifier have any effect on keeping the motor driving the loco across those spots on the rails where there are "dropouts"?

Is the rectifier supplying driving current to the motor after rectifying the AC signal from the track?  If so, then you've got that "gobble it up before it can be used"  from the low resistance motor, haven't you?

I'm just not seeing it clearly.

Thanks,

Bad Order Hal

Sounds like you need to clean the wheels.  It's simple to do.  I cut a paper towel about 6" wide, lay it across the tracks and squirt Goo Gone on it.  Holding the diesel back while under power run one truck on to the wet paper towel.  Pull it back and allow it to go on and off the towel again several times in wet but clean areas of the towel.  Then run the same truck onto a dry section of paper towel to finish it off.  When one truck is clean do the same with the other one.  I do this perhaps once a year for my diesels.

Ed Rappe

HEY ED,

I really appreciate that tip!

I'll bet that will be the solution!  

Bad Order

HEY SCOTT,

What is still confusing me is the use of the word "decoder".  I've always thought of a decoder as an active device that converts a series of digits or pulses into intelligible data, such as Text or Images or Sounds, not as having to do with a power supply.

This is my present stumbling block in the discussion.

Bad Order

Hi Hal,

The decoder is the electronic module inside the loco that "controls" the amount of current and polarity (for direction of travel) sent to motor (along with controlling onboard lighting, sounds, etc.).  Again, think of it as a little electronic throttle (but does not supply power, it needs to consume it)   The decoder needs power to run itself (it is an electronics circuit itself) as well as control the current sent to the motor for speed and direction.  Under normal operation, the decoder gets its power via pickup from the rails, but when a power interruption occurs, it can use a Keep Alive to continue to power itself (the decoder module), as well as use that same Keep Alive for a source of power to drive the motor until power from the rails is restored so the locomotive doesn't stop at dead spots in the track.

Scott K.

Don't sweat it. You'll get it. Technically all command receivers in model trains are decoders as the decode the digital commands and take the appropriate action. They just call them receivers for TMCC and DCS. I think the DCC terminology is more accurate, though some might disagree.

HEY SCOTT once more.....

You said in an earlier post that the decoder supplies power to the drive motor from the output of its rectifier, which is DC.  So does this mean that the decoder output AND the keep-alive capacitor are both across the motor, with the motor constantly depleting the capacitor's charge?

If this is the case, then I just forgot my name.

redrO daB

Ed, if I may ask, any updates on your RR build? I can't remember where your pictures of the layout were.

Joe

 The track is complete and scenery at about 10%.  I've held off posting photos as partial scenery isn't very interesting to most folks.  That said I'm having fun.

Ed Rappe

Hi Hal,

Very nice Dobsonian!

I just wish the skies around here in my part of the northeast were dark enough to do one justice.

Jim

I understand the frustration, Hal.

Add to that the fact that just when you get really excited about an evening with the telescope, in come the clouds!

That's the nice thing about the trains. If you are in the mood, you can be sure they will run.

Jim

The setup you are proposing will not get rid of the dirty track/wheels problem.  The capacitor discussed will help but..   The MRC "wireless" system is only wireless from the cab to the command base which then still uses the track and track power to command and power the decoders/locomotives. 

The wireless being discussed elsewhere has no command base. In fact there is no power to the rails at all.  If power to the rails is required at all the dirty rail/wheels problem will still be there.

HEY JIM,

What frustration?  There's only relief!

Up in the High Desert, when it looks like it'll be an overcast night, then it always clears up!

But they can have their clear skies and telescopes...I've been there and done that!

BAD ORDER

hey rdunniii,

What wireless being discussed elsewhere?

By "cab", do you mean the hand unit? 

Also, what is the "command base"?

People assume that I know what all these terms mean.

bad order

OK, Hal I understand where you are coming from. Ed, gave you good advice about cleaning the wheels. That's the way I would do it.

rdunnii, he knows that. He is getting the wireless remote so he can be standing next to the locomotive when (or should I say if) it stalls.

Hal, the cab is the remote you hold in your hand that controls the trains. Regardless if it wireless or not it is still called a "cab". It can also be called a "Handheld" or a "Throttle". The Command Base is the box that gets the instructions from the cab and converts them to the DCC signal and sends them to the Power Booster also sometimes called a Power Station. On some systems the Command Base and the Power Booster may be integrated into one box. The DCC signal is a square wave. The Power Booster in turn amplifies the signal and then sends it out on the rails. The signal which includes digital instructions (packets) and power is received by the locomotive through its decoder. The decoder decodes the 1s and 0s of the square wave and performs the appropriate instructions. Of course it will only perform the instructions if the address of the locomotive matches the address of the instructions.

HEY HUDSON,

THANK YOU!

Your explanation is the clearest I've read in this discussion! 

I would assume that the parameters of the square wave (pulse width, pulse frequency), would determine the nature of the command as received in the Locomotive.

Here's a picture of my Electronics Lab, where I'm re-calibrating the Siderial tracking rate of my 8" Schmidt-Cassegrain telescope from Celestron.

Bad Order Hal

Hey Hal good morning, I have been following your thread with interest. You might want to check tis thread out.  Doug

https://ogrforum.com/t...66#29868550253944066

Thanks, Doug. (Suzukovich sounds like a Yugoslav name.)

The discussions were interesting.

Bad Order

It is Serbian.

You are correct sir!