RailPro > RailPro Specific Help & Discussion
Keep Alive installation w/ Railpro
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 Vcc 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 Vcc 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.
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