With Keep Alive's allowing trains to keep moving, what would happen if you used more than one and if so, how many. What am I missing.
rrebell With Keep Alive's allowing trains to keep moving, what would happen if you used more than one and if so, how many. What am I missing.
Simon
Thats what I was wondering, kinda like hybred dead rail much easier than true dead rail.
If you loose power to the rails, the loco would do one of three things:
With regular DCC it would not be like dead rail because without track power you have no way of communincating DCC commands to the locomotive.
Five million dollars worth of capacitor hybrid technology, we were only able to keep it on the road for a few months.
This was a first generation field test of the technology. It was a fascinating project, and paved the way for much better stuff to come.
-Kevin
Living the dream.
LastspikemikePlus high energy capacitors have safety issues associated
huh? at model railroad voltage?
greg - Philadelphia & Reading / Reading
rrebellwhat would happen if you used more than one
the larger the capacitance, the longer it would run without track power
CSX Robert rrebell With Keep Alive's allowing trains to keep moving, what would happen if you used more than one and if so, how many. What am I missing. If you loose power to the rails, the loco would do one of three things: Continue running until the "keep alives" ran down. Continue running until it reached the decoder's DCC timeout (often adjustable with CV11, the NMRA recommended CV for the timeout value). Continue running until it ran into something or off the track. With regular DCC it would not be like dead rail because without track power you have no way of communincating DCC commands to the locomotive.
To that list I would add:
4. Continue running until it hits rails that are powered by the DCC system (back to normal). This is what typically happens.
I have seen stuffed animals with safety warnings.
LastspikemikeI had understood that capacitor voltage is regulated down to the desired output operating voltage but outside the capacitor itself
the capacitor(s) in a keep alive is charged to track voltage (~14V).
when track power is lost, it supplies current to the motor and decoder which has a regulator to drop the voltage to 5/3.3V. the motor operates at the capacitor voltage which steadily decreases until track power is resumes
Hi rrebell,
In my opinion (which is probably useless), if the track and wheels are clean and there are sufficient power feeds, the need for keep alives should be minimal. I use them in my two axle critters mostly to get them through turnouts. I don't use them in any of my larger locomotives because, if the above conditions are met, the locomotive should never lose power.
I think that installing larger capacitance is actually a recipe for disaster. If the keep alive can power the locomotive for let's say 10 seconds, the locomotive is going to keep moving for 10 seconds without any control. That will surely lead to collisions and/or trips to the floor. If you say that you can just hit the stop button, that won't work. If the stop command does work that means that the locomotive is receiving power and control signals from the track. That would mean that there is no need for a keep alive at that point.
I use Loksound 'Power Pack' keep alives. They allow the duration of the keep alive output to be controlled. I set mine for about one second which is more than sufficient in my experience.
Cheers!!
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
LastspikemikeThe topic was about powering a locomotive with larger capacitors than a keepalive.
yes it is.
regardless of the size of a capacitor, 0.1uF or 4F, it's the voltage rating that is cause for concern (a possible danger).
just as you probably don't want to touch the leads of a 100V power supply, you wouldn't want to touch the leads of a capacitor charged to 100V. (you certainly have no worries about touching the rails of a track at ~14V)
when people discuss using larger capacitors for keep alives, they aren't suggesting higher voltage capacitors. either they are suggesting using additional capacitors wired in parallel or using larger capacitance capacitors (e.g. 1F). in either case, the voltage rating of the capacitors need only be ~16V and even if rated higher, would only ever be charged to track voltage, ~14V
The capacitor may charge to the highest available voltage, which for power AC can be peak rather than RMS (it is common for smoothing capacitors to reach something like 161V on a nominal 120V line) but this is immaterial for any DC system, of course, and DCC modulation does not behave different from 14VDC or so with respect to keep-alives.
You can easily use voltage-to-voltage conversion to regulate the 'output' voltage from a capacitor as it discharges -- both to lower it when fully charged, and boost it when nearly discharged. That is little different from voltage management when using a battery.
This reminds me of some of the 19th-Century theories of locomotive boiler explosions, which supposedly involved 'thousands abd thousands of psi' of instantaneous explosion pressure if the 'supercritical' water were suddenly depressurized. It turns out you can certainly generate that kind of force... but not as steam pressure, and a moment's reflection should show you why not
LastspikemikeI referred only to high energy capacitors. I've seen warning labels on high energy capacitors.
certainly you need to be careful with high voltage capacitors.
i worked on a laser in college that used a couple 4F 600V capacitors (4x4x8"). we used a battery cable to discharge the capacitor after use. it made a very audible crack when we did.
LastspikemikeHow "big" would a 14volt capacitor have to be to power an HO locomotive in a useful way.
i calculated in the "Keep alive device, worth it thread?" that 4 1F 5.5V super caps in series stores 3.6 coulomb, 52 joules of energy.
a 1F 5.5V super-cap is about the size of 3 knickles stacked together.
More than one what? A Keep Alive on each and every locomotive?
What am I missing?
Rich
Alton Junction
To make it simple a capasitor like Keep Alive can power some engines for two feet, so if that is the case, then what happens with more, can it go 10 feet or?
gregcit made a very audible crack when we did.
The bus that I posted a picture of earlier sounded like an MG42 firing a full belt when it accelerated under capacitive/generator hybrid power. The noise was extremely annoying to passengers, and anyone else within 100 yards.
rrebell ...then what happens with more, can it go 10 feet or?
...then what happens with more, can it go 10 feet or?
Thanks for clearing up your question.
The answer is: "Yes!"
Ed
SeeYou190 gregcit made a very audible crack when we did.The bus that I posted a picture of earlier sounded like an MG42 firing a full belt when it accelerated under capacitive/generator hybrid power. The noise was extremely annoying to passengers, and anyone else within 100 yards.
OvermodWhy in hell would it do that?
Can't talk too much about it.
That bus was powered by a Ford V10 NZE gasoline fueled industrial engine that drove a stationary permanent field 400 volt DC generator, The engine had three speeds, 1800, 2400, and 4800 RPM.
There was a large electric motor that drove the rear axle. There was also a small 24 volt DC generator that ran all the bus electrics. The production vehicles using this drive (none were ever built) would not have had the 24 volt system.
To add to the complication, the Ford engine had a 12 volt starting and control system, and its own seperate low voltage components.
The Hybrid part was the capacitors in that box on the roof, and I was NEVER allowed in there. We had to get a field technician from the company in Arizona whenever the capacitor system had issues.
Anyway, how it was explained to me, was that when the capacitors discharged the current level was so high that it was basically a short circuit. I never saw the capacitors or relays, but there were dozens of 4/0 cables running into that box.
It was loud, and that bus was FUN to drive. It was like a 56 passenger funny car. It would smoke the rears from a stop.
Only three of this design were ever built, that is why the five million price tag. It is still on the LeeTran yard in Fort Myers. It has not run in over ten years. I am sure I could get us in if you want to see it.
It should be in a transportation museum.
LastspikemikeThe current keepalives are to keep the sound decoder alive not the locomotive. The flywheels keep the locomotive moving. Adding more keepalives to keep the locomotive moving raises the topics of dead rail and locomotive control.
Keep alives send current to the motor, keeping the motor rotating, therefore, the locomotive moving.
If you run your KA loco, then shut off the DCC system, the loco will continue to run much farther than what the flywheels alone could carry it.
That's what happens with bad track or wheels, no electrical pickup for a spat, and the KA keeps the motor moving.
I think the advantage of capacitors in a KA application is that they can be "charged" very quickly "in circuit" with power from the rails. Batteries require much more time to achieve operational readiness and that would preclude needing powered rails.
- Douglas
Lastspikemike The current keepalives are to keep the sound decoder alive not the locomotive...
The current keepalives are to keep the sound decoder alive not the locomotive...
Doughless...Keep alives send current to the motor, keeping the motor rotating, therefore, the locomotive moving...
Some keep alives only power the sound while others power the entire locomotive.
Lastspikemike... Onboard capacitor power storage raises the issue of separating out the DCC control signal such as LocoFi does, a feature I've advocated for elsewhere. If the control signal could be preserved as a separately powered transmission to the locomotive control board then adding more keepalive capacitors could usefully compensate for bad track continuity by supplementing flywheel momentum...
Onboard capacitor power storage raises the issue of separating out the DCC control signal such as LocoFi does, a feature I've advocated for elsewhere.
If the control signal could be preserved as a separately powered transmission to the locomotive control board then adding more keepalive capacitors could usefully compensate for bad track continuity by supplementing flywheel momentum...
Seperating out the DCC signal is not that hard and has already been done:
http://www.cvpusa.com/airwire_system.php
See, I knew it would be complicated and above my pay grade.
rrebell See, I knew it would be complicated and above my pay grade.
Lucky you! You have experts like us to help you out! Some of us are even right. Sometimes.
Anyway, many/most sound decoders have a capacitor on them. It is NOT a "keep alive". It is there for sound purposes only. It will NOT help propel the locomotive.
A "keep alive", by definition, is there to power the entire locomotive through a dead spot.
That capacitor on the board is NOT.
CSX Robert Some keep alives only power the sound while others power the entire locomotive.
Who sells a "keep alive" that only powers the sound?
Lastspikemike The locomotive would keep moving even if the keepalive weren't there. Apart from short locomotives or steamer with left side at the front of the wheelbase and left side at the rear a keepalive is only there to stop the sound decoder dropping out. You don't need a keepalive on a DC locomotive or a DCC motor only equipped locomotive. The devices are to stop sound decoders dropping out. For non sound decoders the power storage is way in excess of anything bad track might require. Locomotives with flywheels will pass easily over track power interruptions that will cause a sound decoder to drop out, Just because a device does something else in addition to its main purpose doesn't mean that's why it's there. As for it being "by defintion" for locomotive power, not according to TCS: https://tcsdcc.com/keepalive and since TCS claims rights to the brand name "Keep-alive" what they say is by definition correct.
The locomotive would keep moving even if the keepalive weren't there. Apart from short locomotives or steamer with left side at the front of the wheelbase and left side at the rear a keepalive is only there to stop the sound decoder dropping out. You don't need a keepalive on a DC locomotive or a DCC motor only equipped locomotive. The devices are to stop sound decoders dropping out. For non sound decoders the power storage is way in excess of anything bad track might require. Locomotives with flywheels will pass easily over track power interruptions that will cause a sound decoder to drop out,
Just because a device does something else in addition to its main purpose doesn't mean that's why it's there.
As for it being "by defintion" for locomotive power, not according to TCS:
https://tcsdcc.com/keepalive
and since TCS claims rights to the brand name "Keep-alive" what they say is by definition correct.
Lastspikemike The locomotive would keep moving even if the keepalive weren't there. Apart from short locomotives or steamer with left side at the front of the wheelbase and left side at the rear a keepalive is only there to stop the sound decoder dropping out. You don't need a keepalive on a DC locomotive or a DCC motor only equipped locomotive...
The locomotive would keep moving even if the keepalive weren't there. Apart from short locomotives or steamer with left side at the front of the wheelbase and left side at the rear a keepalive is only there to stop the sound decoder dropping out. You don't need a keepalive on a DC locomotive or a DCC motor only equipped locomotive...
The first commmercial "keep alive" was the Lenz USP, for Lenz decoders. Lenz doesn't even make sound decoders.
7j43kWho sells a "keep alive" that only powers the sound? Ed
Digitrax sound decoders have a keep-alive circuit for the sound portion of the decoder. I realize that "Keep-Alive" is trademarked by TCS, but it is also a common phrase used to describe any such circuit for decoders.
SeeYou190that bus was FUN to drive. It was like a 56 passenger funny car. It would smoke the rears from a stop.
See what you can do about getting us in there. That's a whole generation of tech I likely know little about... and I'd like to see how it was done.
CSX Robert Lastspikemike The locomotive would keep moving even if the keepalive weren't there. Apart from short locomotives or steamer with left side at the front of the wheelbase and left side at the rear a keepalive is only there to stop the sound decoder dropping out. You don't need a keepalive on a DC locomotive or a DCC motor only equipped locomotive... The first commmercial "keep alive" was the Lenz USP, for Lenz decoders. Lenz doesn't even make sound decoders. 7j43k Who sells a "keep alive" that only powers the sound? Ed Digitrax sound decoders have a keep-alive circuit for the sound portion of the decoder. I realize that "Keep-Alive" is trademarked by TCS, but it is also a common phrase used to describe any such circuit for decoders.
7j43k Who sells a "keep alive" that only powers the sound? Ed
That's why I put "keep alive" in quotes. Yes, I know there is a circuit in some sound decoders that helps keep the sound from dropping out.
It is better not to call that "keep alive", as it tends to confuse people, including some on this topic.
I'll note that Walthers makes a nice little SOUNDLESS switcher with a "keep alive" included.
The company that makes Keep Alive has already lost it to common lanquage just as kleenex is now used for tissue. In fact Google is fast losing exclusive rights already as everyone I know says google it for go search the internet. In Googles case it may accually end up a benifit.