Referencing this thread in your blog is fine with me, Rick. But you might change one thing. That link to sumidacrossing you tagged as "courtesy of MMagliaro". That kind of makes it sound like I wrote all that stuff on that website, which I did not. I think you should just reference the page and the actual author of that page for the credit, not me.
Coker, what are you hiding from us? Doug G., Mr. Mmagliaro, Coker, CSX Robert, and Ron. If I missed someone, it isn't intentional. I went to lunch with a friend of mine and talked to him about this very subject. I asked him about the oscilloscope and he said true DC would be a straight line. I asked him about the upward blips and he said that's AC. Saying it dirty DC. I asked him about the difference between Pulse Power and a Transistorized Throttle. He then said pulse power uses AC to to get the motor to roll over and is usually associated with an older type of wire wound rheostat. The newer Transistorized Throttle is a pot., that controls the power out to the electric motor and it to uses AC to nudge the electric motor. The only way to get purified DC is to use a car battery or battery of choice. I said hanging my head.:wideeyes: If any of this sounds familiar it's because it's already been covered here. Just not by me. Now I really do hate admitting I was wrong and of course there is the embarrassment that I've done this in front of friend. But I did it all by myself. No, I'm not going to apologize but I will concede, I was wrong. I'd still recommend that you seek out the safer throttles and power supplies to work with. Oh yes, I'm curious but Coker, I'm not going to ask I've had enough for one day. See you around the train layout.
I get the point and will make the correction. I will acknowledge a shout out of thanks to you, for bringing this to my attention. Now where are those darn crows when a guy needs to eat one?
Don't worry Rick, it just takes an understanding of electrical principles. DC current is when the current always flows in the same direction. AC current is when the current flows one way for awhile and then reverses and flows the opposite way for another while. Of course, this is simplified and there can be many variations in the amount of time it flows in one direction and then the other. Hence saw tooth, triangle (so-called), square, and other waveform shapes. And, if you could see it, it wouldn't look like it does on an oscilloscope. That's just a convenient way of looking at it. It would actually look like something bouncing back-and-forth from right to left and left to right, over and over again, in front of your eyes. There really is no such thing as DC spikes because, as soon as the current spikes and then goes back to zero, it has become AC no matter what the decay time, even if it's almost immediate. Any change in current direction flowing to an N scale electric motor (or other things but I like to reference our favorite use of electricity) is AC and can be called pulse. It doesn't matter if it's a result of half-wave rectification, which the older original power packs used, or pulses created via active solid state circuitry (transistors), which relatively modern power packs (although they have been around for many years now - Linn Westcott's TAT III and IV were in the early to late sixties) use. It works because the momentary pulses are temporary increased current and attract and repulse the armature segments to and from the stationary motor magnets more vigorously than steady DC current. One other thing, a transformer is only part of a power pack. It is the device that steps voltage either up or down from the incoming current The output is still AC and must be rectified (changed to DC) to be usable by a permanent magnet motor. Nifty, huh. Doug
Yup. And an acrid, warm smell, sometimes accompanied by smoke and even flames means 'OOPS, I goofed'!
Well, Rick, I for one don't want you to eat one bite of "crow". You went and asked about it, and you even came back here to explain that you were mistaken. Nobody stops getting better or smarter in this world as long as they correct their mistakes and keep moving forward. Cheers and good on ya.
It still may not be clear to everyone that either a wire wound rheostat or the combination of a pot(entiometer) and a transistor is merely a means to adjust the voltage reaching the electric motor. The waveform of that voltage being adjusted - regardless of whether it is pure, filtered, flat DC or includes some form of pulses - is an entirely separate issue. Older power packs with a wire wound rheostat for speed control - that coincidentally had a pulse power feature - would have derived those pulses from the incoming AC power. Newer power packs with the combination of a potentiometer and a transistor for speed control - that coincidentally have a pulse power feature - may either derive those pulses from the incoming AC power or from a separate oscillator circuit, which could generate a waveform of arbitrary shape (and frequency), be it sine, triangle or square wave. The situation is not quite that dire. Consider this circuit diagram for the Kato power pack: As it stands, the combination of a potentiometer and a transistor is used to adjust a DC voltage that is "rippled" or "unfiltered" (or unflat or unpure) - in other words, it contains some AC or pulsed component. There are at least two options that will result in pure, filtered, flat DC reaching the electric motor in the locomotive. One is to add a sufficiently large capacitor at the output of the bridge rectifier - something on the order of 1,000uF with a minimum rating of 35V. This will filter the DC voltage and eliminate the AC ripple/pulse component. Since the connection points that need to be accessed are brought out as the "accessory power" terminals, this modification could be made without having to open up the power pack. The other solution is simply to replace the supplied AC-in/AC-out "wall-wart" power transformer with a different AC-in/DC-out type unit whose output produces pure, filtered, flat DC.
Thanks guys for letting me down easy. A shout out of thanks to Doug G. Ron McF, Mr. Mmagliaro, Point 353, and all who have put in here on TrainBoard. Now there are some things that still don't make sense to me but hey, I don't have to understand all of it. My pedigree didn't prepare me for such things. Thanks for allowing me to avoid eating crow, it doesn't taste very good so I went for some humble pie alamode. Not bad. I can handle that. But I must warn you. I embedded a link to this discussion on BarstowRick.com. So other's interested in this same subject can visit here and take in the fine expertise demonstrated here. Nice job and if I didn't say thank-y0u before. Thank-you! Now back to my fox hole to see what other trouble I can get into.
I completely agree with this explanation. And I might add, not only does "smooth" vs "pulse" have nothing to do with whether the throttle uses a rheostat or a transistors, it also has nothing to do with whether the throttle has a momentum feature. There are four properties of throttles being considered here. 1. Rheostat or transistors (or a regulator, or any of a number of other methods to control voltage) 2. Momentum or not 3. Pulse or not 4. If you have pulse, what KIND of pulse ( could be AC ripple or an oscillator ) These are 4 completely separate and independent functions, and having any of them does not in any way imply anything about the others. Funny thing about that Kato pack. It is the most basic transistor throttle circuit one could ask for, and yet it works surprisingly well. That is one thing that has changed "since the old days". Motors still need some pulse to run well at low speed, but the pulse can be quite simple and gentle, and that means a good throttle circuit can be pretty darn simple as well.
Well I am still following this thread although the caboose I am in became uncoupled a long time ago.hboy: Just another question. I tested my locomotive with a 9 volt battery and it runs fine. What wavelength does the battery use ?
A battery is one of the few things that truly puts out smooth DC. There is no "waveform", no "wavelength", no pulse. It is a flat-line 9 volts. 9 volts will make the motor run pretty fast, however. For low-speed operation, you need to be able to get the motor turning at 2 volts or maybe 3 depending on how low the engine is geared. With a DCC decoder in there, which your engine has, that complicates things because the decoder needs a certain minimum before it will even pass the DC through to the motor on a straight DC system like you are planning to use. So the engine may not move at all until you get up around 5 volts. Some DCC equipped engines need a lot more, even at high as 9v, before they will move on plain DC. If your engine runs to your liking, and runs as slow as you ever plan to run it, on a 9v battery, then you will have no problems with almost any throttle or power pack you buy. You can boil this long thread down to a few key facts. 1. Almost any DC powerpack or throttle you can find is going to have some form of pulses in its output, regardless of whether the maker says so, and regardless of whether the throttle has momentum 2. If you go with any of the recent offerings from MRC, the form of pulses will most likely do a great job running your engine, will not confuse the decoder, and will not harm anything. This is also true of the Kato power pack. The Tech 6 or Tech 7 should be fine. The other ones suggested by BarstowRick should be fine. The Railpower 1300 should be fine. The older-line MRC packs like the Tech II 2500 or 2400, well, that's a gray area. They should work fine, but they do use a stronger pulse that you probably don't need. I have a personal preference for staying away from the 2500 because you can't turn the pulses off and it uses a very strong pulse that I don't care for. Again, I can't prove it does any harm. I've had them here. I've run my engines on a 2500, and nothing bad happened. I just don't like the motor noise. 3. Don't get anything that says it uses PWM (Pulse Wave Modulation) because that might confuse your decoder and make the engine run poorly. Good luck. I'm sorry we all confused and complicated your life. But the understanding of what throttles and power packs really do, and how different types of motors will react to them, plus how a DCC-equipped engine will react, is not a simple subject anymore. I wish it were as simple as just "hook up any old power pack and run", but it's not.
Exactly. You will be much further ahead if you have at least some understanding of how power packs/throttles work and their interaction with locomotive motors. Incidentally, I just received an MRC Tech II 2500 I got on ebay for 20 bucks and it's like new. It works great and I don't really notice increased noise although that is partly due to newer locos having much better motors than the old ones with their loose bearings (and everything else generally being much looser), letting the armature vibrate like crazy in there. EDIT: Bah, I should add that I have had an MRC Tech II 1500 for many years and it and the 2500 are basically the same except the 2500 can handle a bigger load. So, it's not like I'm new to the characteristics of these packs. Doug
