Keep alive

[joe323]

B. Bryce

That is the "Double Edge Sword" situation of the Stay Alive.  It works great when you need it to work, like dirty track, bad connections, frogs, etc, but on the other hand, when you need to stop the loco by killing power, it will not stop until the Stay Alive caps have finished bleeding off.  I saw a situation at our train club layout where a collision was eminant and the operator tried to stop it by hitting the kill switch, but the loco he needed to stop kept on going due to the Stay Alive and the trains collided.  Not much damage, but there could have been.  Also, in addition to running out of track, some people wire turnouts with sections of isolated track entering the turnout which are powered by the frog circuit to stop a locomotive from entering a turnout that is in the wrong position.  Stay alive prevents this from working also.  You must keep this in mind.  Double Edge Sword!

 

Understood but since I have a slow speed switching layout with no track near the edge I think it will be okay.  Thanks to all who replied.

[B. Bryce]

That is the "Double Edge Sword" situation of the Stay Alive.  It works great when you need it to work, like dirty track, bad connections, frogs, etc, but on the other hand, when you need to stop the loco by killing power, it will not stop until the Stay Alive caps have finished bleeding off.  I saw a situation at our train club layout where a collision was eminant and the operator tried to stop it by hitting the kill switch, but the loco he needed to stop kept on going due to the Stay Alive and the trains collided.  Not much damage, but there could have been.  Also, in addition to running out of track, some people wire turnouts with sections of isolated track entering the turnout which are powered by the frog circuit to stop a locomotive from entering a turnout that is in the wrong position.  Stay alive prevents this from working also.  You must keep this in mind.  Double Edge Sword!

[Mark R.]

rrinker

 Thie nice thing about the three wire ones, at least for ESU decoders, is that in addition to staying out of the way when programming, they also can set a maximum run time, instead of just running until the capacitor is discharged. My Walthers Plymouth with a Soundtraxx motor decoder and stay alive will easily run 10 feet or more OFF the track until the capacitor runs out of energy. That's far in excess of what you'd ever need to get over a switch frog or a small spot of dirt on the track. I don't run my track right at the very edge of the benchwork, but I don't keep it 10 feet away, either. That little switcher could derail and rampage across the countryside and right over the abyss if there are no trees, bushes, or structures in the way.

                            --Randy

 

 

The time adjustment on Loksound decoders also works with the two wire versions as well.

Mark.

[rrinker]

 Thie nice thing about the three wire ones, at least for ESU decoders, is that in addition to staying out of the way when programming, they also can set a maximum run time, instead of just running until the capacitor is discharged. My Walthers Plymouth with a Soundtraxx motor decoder and stay alive will easily run 10 feet or more OFF the track until the capacitor runs out of energy. That's far in excess of what you'd ever need to get over a switch frog or a small spot of dirt on the track. I don't run my track right at the very edge of the benchwork, but I don't keep it 10 feet away, either. That little switcher could derail and rampage across the countryside and right over the abyss if there are no trees, bushes, or structures in the way.

                            --Randy

 

[gmpullman]

richg1998

It is not odd at all.

Maybe I should have phrased it something like "takes a while to get used to..."

richg1998

The keep alives are energy storage devices.

I agree.

Thanks, Ed

[richg1998]

It is not odd at all.

The keep alives are energy storage devices. When you shut the DCC power off, the keep alive is still powerd up, stored power. Electrolytic capacitors are storage devices. The decoder is still active. Lights are still on. No way to shut them off. They have to bleed off.

Rich

[gmpullman]

hon30critter

Apparently this can be an issue with two wire keep alives and they may have to be disconnected to allow the programming to work.

I have maybe two-dozen various locomotives and a few of those Soundtraxx Soundcar devices with keep-alives. 

I haven't encountered any problems using Decoder Pro either directly through my Digitrax programming track or with the Sprogg II on my test track.

It does seem odd that when I kill the power to the layout I can still hear diesels idling and steam locomotive air pumps working for almost a minute afterward.

Sometimes I wonder if there will be a "Cap that breaks the Boosters back" when I add that final car or locomotive with keep alive to the layout. By rough estimate I probably have 40 to 50 lighted passenger cars with capacitors installed along with the aforementioned score of locomotives.

Regards, Ed

[hon30critter]

7j43k

Just how fast will it go, wide open, with its 60:1 gearing?

Thanks Ed. I'm not sure if it would get up to 20 scale mph or not. All I can say is that it is very slow, even wide open.

The video was taken on a Peco Code 100 turnout. I have read that the Peco turnouts can be a little wide at the guard rail gaps. That might have been part of the issue.

By the way, the critter is a little more finished in appearance than it was in the test video. I still have to paint the roof and grab irons, and I want to put zebra stripes on the front and back but each time I sit down to do the decals I chicken out!

Here it is at speed step 1. It takes almost seven seconds to go from one tie to the next! When I say 'slow' I mean 'SSSLLLOOOWWWW'.

Dave

[7j43k]

Dave,

Sorry I forgot it was you who did this.  I think you did a GREAT job on that little fella.  Just how fast will it go, wide open, with its 60:1 gearing?  I doubt the real one would get much over 20 mph.

Yeah, that was a big bump at the frog.  I'm having to deal with that, myself.  I looked up the NMRA standards and found that the max depth of an RP25 flange is .028", and the min depth of a flangeway is .025".  Which kind of hints that there shouldn't be much clearance between the two--the standard actually accepts .003" interference.  I'm thinking of having a very small gap, just to avoid that nasty bounce that happens with commercial switches.  My frogs will be all metal, so electrical contact won't be a problem, if locos happen to ride on the flange.  In fact, I will probably slightly ramp the entrances to the flangeway, for obvious reason.

When I've actually DONE my experiment, and if it's successful, it should mean that I can happily run the 88 wheels.  Which I do anyway.  Bumps and all.

Again, thanks for doing this fantastic experiment.  It's quite informative.  And you get to keep the loco afterwards!  What a cutey!

 

Ed

[hon30critter]

7j43k

Someone on this forum did an experiment with a teeny loco, maybe a Grandt.  As I recall, he tried it with a flywheel, and then with a "keep-alive".  The latter won, easily.

Hi Ed,

That would be me. You are correct about the significant improvement that the keep alive made to the locomotive's reliability. It has never stalled. The locomotive was a Grandt Line Boxcab with a BullAnt drive made by Hollywood Foundry in Australia. I used a Loksound Select Micro with a Loksound 'Power Pack' keep alive. Before I installed the keep alive it stalled at the frog every time.

Here is the locomotive in action:

The locomotive drops into the frog gap because I ordered the drive system with Code 88 wheels. They have since been replaced with Code 110 and that solved the problem.

While the performance of the keep alive is amazing, the speed at which it will operate is way too slow to be useful. I ordered the drive with 60:1 gearing. It should have been 30:1 Live and learn.

Something to note about the use of keep alives is that they can cause problems when trying to program the decoder. Apparently this can be an issue with two wire keep alives and they may have to be disconnected to allow the programming to work. The Loksound has three wires and it does not interfere with programming. All you need to do with the two wire systems is install a micro plug between the keep alive and the decoder.

Dave

[7j43k]

richg1998

I do recall some saying flywheels were keep alive for DC locos for many years. I saw the difference over the years when I added flywheels to loco motors with a good can motor or coreless motor.

Rich

 

Except that they're only "keep-alives" when they're turning at "high" speeds.  At really low switching speeds, they don't do much.  That's because their momentum is linearly related to their RPM.  Lots of RPM's, lots of momentum.  Hardly any RPM's, hardly any mometum.  With a real "keep-alive", it works very nicely at very low speeds.

Someone on this forum did an experiment with a teeny loco, maybe a Grandt.  As I recall, he tried it with a flywheel, and then with a "keep-alive".  The latter won, easily.

There is likely no need for flywheels at all in DCC "keep-alive" locomotives.

 

Ed

[richg1998]

I do recall some saying flywheels were keep alive for DC locos for many years. I saw the difference over the years when I added flywheels to loco motors with a good can motor or coreless motor.

The flywheels got the locos over dirty spot and we hardly ever noticed a hesitation. A decoder notices it right away.

Flywheels do not seem to be needed with keep alive.

Rich

[peahrens]

Here is a link where connecting a TCS Keep Alive to several decoder types is described.  I beleive connecting a Soundtraxx Current Keeper is similar; i.e., there are 2 wires.  The LokSound items have 3 wires.

http://www.members.optusnet.com.au/mainnorth/alive.htm

I have added Keep Alive or Current Keeper to about 10% of my locos, but only to LokSound Select decoders.  That involves cutting back the plastic wrapper a bit and soldering to two relatively teeny solder pads.  Not incredibly difficult but I would recomend only if you have some modest soldering experience.

Beyond whether one can be connected there is also the issue of where it will phsically fit.  Note there are several different sizes and shapes of the Keep Alive and Current Keeper.

Another, more expensive, option is to replace the decoder with a TCS version that has a built in Keep Alive, or at least one that has a plug for a Keep Alive easy connection.  LokSounds do not offer a plug-in unfortunately.  I don't know if the newer Tsunami's do or not.

[wvg_ca]

you can add a 'keep alive' to DC loco's, but it's not worth while ..

you need twice the capacitors, resistors, and diodes because the current changes direction depending on the loco's direction, and where you need it the most, at low speeds, the capacitors receive low voltage which effectively reduces thier enhancement ..

you are better off adding in your momentum, if your DC control has that feature  ..

if it matters, i have actually done this

[MisterBeasley]

richg1998

 

 Not the first time this question has been here.

You should study the electronics involved.

Rich

 

On the other hand, this forum may be the best place to connect with the experts with the most practical knowledge.

[richg1998]

joe323

Can one add keep alive caps to existing locomotives?

 

As was said. Keep alive is only for decoders, not DC locos. The devices are not for reverse polarity which you have with DC locos.

Not the first time this question has been here.

You should study the electronics involved.

Rich

[MisterBeasley]

For DCC, you need a circuit like those from TCS, not just caps.  For DCC, you're going to have problems because most big capacitors are electrolytic and will have trouble in reverse.

[BigDaddy]

Assuming you mean DCC, yes and maybe. 

I find this recent thread a little daunting

http://cs.trains.com/mrr/f/744/t/272429.aspx

[joe323]

Can one add keep alive caps to existing locomotives?