Keep Alive installation w/ Railpro

[TwinStar]

Thanks Bill!

[TwinStar]

I purchased a KA3 and a KA4 to check sizing and fitment before ordering the remainder for my fleet. I still operate mostly on top of DCC at Free-mo setups and eliminating the dirty track issues is priority number one.

[CPRail]

Just to make sure I'm reading this correctly - if I install this bridge rectifier, I can add in a TCS Keep Alive module, and it'll play happily regardless of power input (DC or DCC)?

If that's the case, I'll be ordering the rectifiers ASAP!!

[William Brillinger]

Ian, it's true, this solution is DC and DCC friendly.

I proposed this idea a long time ago but never acted on it.
http://model-railroad-hobbyist.com/node/22101

I think I'm ready to proceed too. I'm done waiting for the Ring engineering version of this tech.

[Alan]

Go for it Bill. Chance to make a little pocket change, eh? A resistor, a few supercaps, and a bridge. Sounds eminently doable on a kitchen table assembly line. Uuuu, good idea - encapsulate in black casting resin. Then you can stamp a PDC logo on it.

[William Brillinger]

Alan, no, I don't think I'm going to be making a product here. I really don't want to be responsible for making smoke generators out of people's LM's!

...But I am ready to order some KA3's and KA4's for myself. I already have the Diode Bridges.

[TwinStar]

Bill:

I got tired of waiting too. My bridge rectifiers from DigiKey arrived before I left for work and ebay says I have a KA3 and KA4 waiting in my mailbox for me. I'll post some pics in the install forum this week.

Jacob

[G8B4Life]

Here is some further reading for those that might like to investigate making their own. It would not be hard.

On Marcus' page, about 2/3 way down under "More details of the Stay/Keep Alives." is a pic that shows the TCS KA-1 and KA-2 without the shrink wrap. Further down you can see how he cut a KA-2 in half for a tight installation.

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

There is a pdf file on this site, which on page 8 has a basic schematic of a stay/keep alive. Note the diodes as well as the resistor. From memory TCS has 150 ohm resistors.
 
https://dccconcepts.com/manual/dcc-advice-12-exerpt-b-decoder-standard-connectors-and-stay-alives/

- Tim

[William Brillinger]

DO NOT DO THIS - IT'S A BAD IDEA...

Using a KA with the LM-3 and LM-3S

Here is a Wiring Diagram for the LM-3S



And a few quotes from Ring engineering during previous discussions I had with Tim:

"we changed the name of the wire on the 6 pin from 'Common' to 'Negative'.  This change is because many DCC people call the blue wire common (although it is a positive wire)"

"The LM-3 and LM-3S have a common pin in place of input 2. Therefore they have one input instead of two.  The common pin will allow better compatibility with keep alive and DCC."

"However, since the LM-3 has a common pin you may be able to use one of the other manufacture keep alive's with the LM-3."

And finally the mandatory but covering...
"However, since the LM-3 has a common pin you may be able to use one of the other manufacture keep alive's with the LM-3.  Warning: we do not recommend using any other manufactures keep alive's with our LM's because in the worst case it may cause a fire. Connecting other manufacturers product to our LM-3's may damage our LM-3 or the other product.  Even if one module worked today with our LM-3, we could not guarantee that other manufactures will not change their product such that it is not compatible with our products tomorrow. This would be: try at your own risk."

Theoretically you should be able to connect a TCS KA to the Common and Negative wires (ON THE LM-3 or LM-3S ONLY) and you wouldn't need the Bridge Rectifier.

Has anyone tried this yet?

DO NOT DO THIS - IT'S A BAD IDEA...

[Alan]

Personally, I would be very hesitant to do this. Connecting to the blue and negative LM wires means you are placing the KA after the LM internal V_cc supply conditioning. While this may be the logical point electrically , it also means you are relying on said conditioning circuit to cover your butt in the event of a KA installation misstep or KA failure. Accidentally shorting a LED or motor output is one thing, sudden discharge of many farads of capacitance is another. I shudder to think what the waveform on the V_cc rail would look like when a bank of supercapicitors unload instantaneously. No wonder why Ring makes the disclaimer.

Nope, sorry. Until Ring offers specific assurances regarding the LM internal protection circuitry I would stay with the external bridge. This way, should a problem arise, the potential loss is a 25 cent bridge, not a $70 module.

[William Brillinger]

Good points Alan. I have updated the post with a big fat warning.

[KPack]

Good advice.  I'm glad we have guys who understand electronics on here, because I am amateur at best.

-Kevin

[Alan]

Electronics may work invisibly but water systems don't.

Rail power -> External bridge -> KA -> LM -> Motor =
Well pump -> Check valve -> Tank -> Valve -> Pipe & faucet
What is the flow rate of water coming out of a leak in the pipe? Answer: Only as much as the valve will permit.

Rail power -> LM -> KA -> Motor =
Well pump -> Valve -> Tank -> Pipe & faucet
What is the flow rate of water coming out of a leak in the pipe? Answer: Only as much as the valve will permit plus suddenly every bit of water in the tank.

Supercapaictors are really big tanks!

* the analogy is not completely correct but you get the idea.
 

[William Brillinger]

I'm glad we have guys who understand electronics on here, because I am amateur at best.

Me too!

[William Brillinger]

UPDATE!

I received some Keep Alives last week, which I ended up ordering from Litchfield Station, I wanted to order them from YankeeDabbler, but YD has an error in the price of the KA4 on their website and they never responded to my email or call, which is unusual for them  

I am very pleased with the service from Litchfield, The order came very fast, the price was the same as YD, and when I asked if they would offer free shipping on my $200 order, they did!

I got several TCS KA-3's and TCS KA-4's. they are smaller than I imagined and guess what!?!  THEY WORK!!

I did a test install of a KA-3 tonight into a Kato SD40-2

It worked, nothing exploded and it runs fantastically!
It also keeps the sound going for about 30 to 40 seconds after the power is removed if the motor is not moving.

One issue I did notice is that I am seeing frequent power warnings. No red warnings, just that the power is on the "low" side of good.

Soldering up the Bridge Rectifier:




I marked the + lead on the Bridge Rectifier with sharpie to keep it oriented correctly, and I used red heat shrink to easily identify it later:




I use a quick plug system so I can easily separate the trucks from the module as seen here:




Here you can see the KA-3 with the LM-2S:



As you can see I have a lot of spare wire in that unit, this is because I have not wired in the lights etc. eventually I hope to have  a quick plug set to separate the carbody from the chassis too, then I will shorten everything up. this unit has more work to be done before that happens though.

Cheers!