RailPro > RailPro Specific Help & Discussion
Stay Alive Circuitry
Alan:
Yeah, I think we have two interspersed conversations going on in this thread - battery power and keep alive.
I get why you don't want additional voltage drop. 12v is marginal to begin with (assuming HO). On the keep alive side of this conversation, there is no real problem implementing without waiting for a new pin on a module providing you start with sufficiently high power supply voltage i.e. power supply other than Ring. Of course Ring is not going to recommend that. No businessman would.
It appears your constraint is the S-Cab board restricting you to a single cell. If you could replicate or find a similar battery management board that works with multiple cells then you wouldn't need post-rectifier ground connection. But that opens up the whole dark side of LiPo so it is totally understandable why S-Cab is single cell.
Even the wall power group suffers from an occasional low voltage warning if your layout is of any size. Our power supplies have no external sense line so wiring inductance causes voltage regulation to be slow and sloppy with lots of over/undershoot. Fortunately, RP seems very forgiving of the condition. I have yet to notice any change in train operation when the warning appears. I think the warning trip is so fast it is catching the ringing in the supply line due to load change. The physical mass of the loco driveline totally masks the voltage swings so the voltage ringing isn't observable in the loco itself.
I installed a ballast load to calm down the ringing. Wasted power as heat but does the job.
Supply rail ringing before:
Supply rail after:
Alan:
Anecdotal support:
Years and years ago on a layout far far away I had a helicopter that I wanted to spin up/down realistically. On hand I had four enormous capacitors that had been removed from a broken beefy stereo amplifier. One of those old All Electronics 99 cent gearmotors drove a shaft that went up through the layout to the blades. I put the four huge caps in parallel across the gearmotor terminals and fed 6V through a resistor diode series. Essentially a keep alive all day circuit! :P
The effect was awesome. The caps took so long to charge and discharge with the corresponding slow voltage curve across the gearmotor that the helicopter blades moved very lifelike. It took them several minutes to wind up to speed (or down). A poor man's substitute for pulse width modulation. I wish I had pictures to share but alas it was a time before the luxury of free digital picture taking.
melarson:
--- Quote from: Alan on July 27, 2016, 12:32:32 PM ---1: I get why you don't want additional voltage drop. 12v is marginal to begin with (assuming HO).
2: On the keep alive side of this conversation, there is no real problem implementing without waiting for a new pin on a module providing you start with sufficiently high power supply voltage i.e. power supply other than Ring. Of course Ring is not going to recommend that. No businessman would.
3: It appears your constraint is the S-Cab board restricting you to a single cell. If you could replicate or find a similar battery management board that works with multiple cells then you wouldn't need post-rectifier ground connection. But that opens up the whole dark side of LiPo so it is totally understandable why S-Cab is single cell.
4: Even the wall power group suffers from an occasional low voltage warning if your layout is of any size. Our power supplies have no external sense line so wiring inductance causes voltage regulation to be slow and sloppy with lots of over/undershoot. Fortunately, RP seems very forgiving of the condition. I have yet to notice any change in train operation when the warning appears. I think the warning trip is so fast it is catching the ringing in the supply line due to load change. The physical mass of the loco driveline totally masks the voltage swings so the voltage ringing isn't observable in the loco itself.
5: I installed a ballast load to calm down the ringing. Wasted power as heat but does the job.
--- End quote ---
1) Yup, HO. I'm still considering, against Tim's advice, connecting the BPS output to the 9-pin blue and 6-pin yellow, but tonight I will be taking some measurements to see what is there under normal conditions. I'm hoping it's reasonably close to 12v. Fingers crossed.
2) I agree, and it may not be a problem even with Ring's PS. I don't know what the output voltage level is so I will be measuring that tonight too. I may be worried for nothing. Trust me, it's happened before.
3) I think I have two options with the BPS. The best option is to contact Dr. Stanton to see if he's willing, on a special order basis, to adjust the converter output to, say, 14 volts. That is unlikely but it never hurts to ask. The other option is to place and external DC-DC converter to step the 12v output to 14v. Problem solved but only if I can fit yet another component inside the engine. Argh!
4) I get low voltage alarms frequently when running trains on a loop of Bachmann EZ-Track. Granted the loop is typically around 60 or 70 feet of track, and they do occur more often at the opposite side of the PS connection, but I do get them. When I have the info screen up I can see the fairly wild fluctuation of the track voltage, almost regardless of where the train is located on the loop. And I agree, the train keeps going, but an alarm I can not clear and just have to wait for it to clear itself is kinda frustrating. Guess it's just my personality.
5) I like it. And your results! Just when I thought terminating resistors were a thing of the past. But actually they are still used to this day on lines like ModBus and DeviceNet and probably many other communication lines. Those resistors can dissipate a considerable amount of power; what resistance are you using?
Alan:
--- Quote ---Those resistors can dissipate a considerable amount of power; what resistance are you using?
--- End quote ---
Ha! Funny you should ask.
They are 20 ohm 100 watt units. At 15V that's about 11 watts of heat. Well within the resistor power rating (25W no heat sink, 100W large heat sink) however after particularly long sessions they get quite hot. In excess of 200 F. I don't like that. So, on the bench right now are replacements - three parallel 100 ohm 100 watt resistors for a net of 33 ohms. At 15V that's about 7 watts but spread over much more aluminum.
The ringing is so well dampened at 0.75A I am banking 0.5A will be good enough. China eBay didn't have 60 ohm available and stateside suppliers want $10 each. I bought a lot of 10 for $28.
KPack:
Lol, I'm so confused right now. I'm catching bits and pieces but by and large this terminology is way over my head.
-Kevin
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