RailPro > Finished RailPro Installation Examples
Kato SD40-2 - Deadrail Install with Railpro
Alan:
--- Quote ---Being somewhat electronically challenged, I'm not sure how you are able to run it with sound on only 3.7v?
--- End quote ---
Kevin is using Pololu voltage converter boards from Litchfield Station. They convert the battery voltage from 3.7V up to 12V.
DC voltage up converters work very similar to the ignition system of old cars. In a car, points close allowing low voltage to charge the ignition coil. When the points open the coil discharges at a higher voltage. DC up converters function the same except at a much higher open/close frequency than car points and a much lower coil discharge voltage than an ignition coil. The coil discharge, instead of being sent to a spark plug, is temporarily stored in a capacitor. A regulator then drains the capacitor at 12V output. Before the capacitor runs out of juice the points have closed/opened again repeating the cycle.
EDIT Made an illustration showing the components:
Does that help?
We have to respect the laws of physics. Energy cannot be created, merely transferred. The wattage (power) needed to move the loco and play sound is the same on Kevin's system as it would be on powered rails. W=V*A. The DC up converter board is delivering the same wattage as the rails would be but it is doing so with 3.7V. Therefore, the amperage must be higher to make the equation balance. That is why I am so interested to see how Kevin's loco fares after the battery gets some life on it. New batteries always work good. Aged batteries, not so much.
KPack:
--- Quote --- That is why I am so interested to see how Kevin's loco fares after the battery gets some life on it. New batteries always work good. Aged batteries, not so much.
--- End quote ---
This will be interesting to find out. I don't run a ton unless I'm at someone's place on their layout. So I may not have much to report for a while. Worst case scenario is that the battery ends up going belly up much sooner than I anticipated. But if that happens, I just swap the battery for another one. These things only cost a few bucks a piece....maybe $5-6. Plus batteries will likely improve over time, allowing smaller packages with higher storage capacity (at least I hope).
Anyways, I still need to do some testing with this. I haven't hooked it up to normal Railpro locos yet to see how the start voltage/MU capability is affected. In the end, this locomotive will always be paired with another SD40-2 (ScaleTrains) that will also be battery powered, so any negative effect on the start voltage won't be an issue. I'm building a matched pair of SD40-2's that service my area....#1778 and #1999....they have been coupled together for years now serving the Central Washington area.
-Kevin
nodcc4me:
Kevin, I was actually referring to everything you put in there, including the module, two speakers, Pololu board, battery and plug. I think the low Kato motor does make the difference. Good idea on the brass strip.
Alan, your very cool diagram and narrative does help explain the required voltage gain. In another thread you mentioned that you were just an amateur at this stuff. LIES! ;D
BTW, what program did you use to make the diagram?
Alan:
--- Quote ---These things only cost a few bucks a piece....maybe $5-6.
--- End quote ---
On other forums I am on record as an anti-battery guy. Not because I love track wiring but for two primary reasons, one of which you mentioned:
First, my layout is all first gen 4 axle diesels. Batteries will not fit. Shucks, even an LM won't fit in my S-2s without shedding its plastic case and milling a flywheel! Doubtful batteries will ever be so small in my lifetime as to be practical in a little loco. This restriction is unique to my situation (or others with same). I get that. Not a direct fault of battery technology.
The second and more universally important reason, "These things only cost a few bucks a piece....maybe $5-6" There it is. My Fitbit made me aware I walk far more steps in a day than I would have ever guessed. I suspect the same may be true with hours on a loco. I like to play with trains and have a fair bit of track to do so on with quite a few locos. The life expectancy of a battery worries me greatly. If I had to install a new battery in each loco every year or even every other year, the operating cost would get ridiculous especially when compared to a one-time-purchase of power supply and wire. And I would still be left with locos that have to be charged regularly. Cell phone and power tool ownership has clearly demonstrated to me batteries are great when new. Two years of use later they peter out fast.
I dwell on this subject because way back in the LK&O design days I seriously considered battery power. You have to admit, there is a strong allure to having no track wiring. I am not trying to make my equipment run on other folk's crappy track nor am I too lazy to properly clean my track. Battery power makes no sense. Am I missing something? :-\
KPack:
Alan - Batteries with their size and possibly long-term failure, make them less than desirable in many cases. I can fit them in my locos (though with some difficulty....milling that frame took forever), but mine are also MUCH larger than what you have. With my SD40-2, I can easily pop the hatch and plug in it, but with other locos (SD70 family, any GE) I can't, so I'd have to come up with another solution if I were to use battery power....have the plug in the fuel tank, etc.
Would I ever convert all my locomotives to full battery? No. At most I will do this and the other SD40-2 I mentioned earlier. As it stands right now I don't feel that battery is practical for the long term, but I have to admit it is a blast to play around with. The fact that the locomotive will never stall, ever, on any track, is appealing. But I don't relish the idea that constant battery replacements may in order for the long term.
Arguably the best way forward to prevent the occasional power loss problems would be to do a keep-alive, as has been discussed in the other thread. I don't think that layout wiring is going away anytime soon, so might as well use it and keep-alives to maintain a constant source of power to the module. That is probably the route I will take on the remainder of my fleet. I have several locomotives that never lose power, but many others that seem to be more prone it. A bridge rectifier and KA would make easy work of that problem.
-Kevin
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