jward:

The Circuitron auto reversing is after the throttle electrically and momentum in the throttle would get shut off early by the relay that does the auto reversing. The resistors might work. I'll think about it. I am aware of blocks as my 1950's DC layout had about five of them in the layout with two throttles (one block was a reversing track) that I had to manually manipulate to reverse train direction. At junior high school age and without help (my father was not into electrics) I learned a lot about electricity. That experience of wiring up that layout fostered my interest in electronics. Electronics became my living after college (BSEE) for over 30 years. That layout was the key to my future.  The layout was removed after I entered high school. I did resurrect the old rolling stock  on a very small layout for my son in the 1980's but the old stuff eventually died as did his interest and mine.

richg:

I was thinking the same thing but if the transformer and the circuitry could handle the inrush it might work. I doubt the little Bachmann power pak is heavy duty enough and may even have internal current limiting. The slowdown is not the problem if I have delay until the polarity changes but when the relay turns the power back on there definitely would be an inrush of current. This may be a bad idea. It was just food for thought.

Thanks for the inputs.

LDBennett

I have a special case DC powered small trolley layout. It is an 8 feet long straight track that runs in front of a small town scene. My goal is to allow it to run for hours unattended. To that end I have installed a Circuitron auto point to point system with two intermediate stop points with variable delay for the stop length. It works with photo detectors in the track. The end ones stop the trolley, wait for the delay to time out then reverse the DC voltage to the track. The intermediate detectors stop the trolley, wait for the delay to time out, and then proceed.

Depending on the speed selected for the trolley the stops and a starts are abrupt. I was thinking of adding a large capacitor to the track wiring so that when the control circuit removes the DC from the track for the stop, the capacitor will act like a big battery and taper the speed off over the time period of part of a second. When the power is returned to the track the capacitor will have to charge up so the startup of the trolley will be a bit less abrupt.

But here's the problem: If there is NO delay then the capacitor will not have time to discharge before the polarity changes. That will mean the power supply (the throttle power source) will be looking in to a reverse charged capacitor and a large inrush of current will flow from the throttle power supply. As long as I make it so there is always a delay at the ends of the trolley run there should be no problem. But when the DC power comes back after the delay there will be a smaller inrush of current.

I fear for the life of the Bachmann small throttle power supply. Should I?

Anyone got any insight into this.

Can one of the momentum circuits I see advertised work in this scenerio?

Sorry for all the questions but while I am doing the scenery and setting up the buildings, my engineering mind keeps wandering. The correct approach would be to use the photo detectors in concert with a microprocessor  running a custom program to control everything in a random way. But I just don't think I want to make this a long project. I just want to "get it done". So I keep gravitating towards simple and easy fixes. I know, not good, but it is what it is. I have limited time (I have to help my 11 year old grandson get his N gage setup going since the cat ruined it and I need to do some motorcycling, some photograph, some camping, etc...). It's hell being retired as there is never enough time to do everything!

LDBennett

 ebtnut:

I never would have guessed there was a difference in the sounds. Thanks for the info.

richg:

I went to the link and it was interesting. But for my non-DCC trolleys and little layout I was just thinking of a stationary sound source. The one from Dallee can be hooked up to detect current going to the tracks (trolley in motion) to make startup and stopping noises and offers push button controls on thing like the bells, etc. The problem is their current model for trolleys is for the latest greatest modern trolley (Is it the RD?). That won't do but as I said earlier they are working on a PCC version. That will have to do for my Birney and my Peter Witt although it is probably the wrong sounds (oh well). Thanks for you info.

LDBennett

I found that Dallee is working on a trolley sounds system, what they call TRACTION / TROLLEY CAR SOUNDS. But it is months away. Is there another sound system that covers traction/trolley sounds? The picture in the Dallee catalog, announcing it as a future product, is of a common street car that might have run in the 1950's and pretty much match the PCC streetcar by Bachmann.

LDBennett

I had the same question and others here told me to pull the DCC board and replace it with the dummy plug. The Trolley did run with the DCC board installed on my DC layout but it seemed a bit balky at low speeds. I replace the DCC decoder with the dummy board and both my trolleys run better. It is a good thing to do for those of us that still have DC power layouts.

LDBennett

I finally got the little layout all wired with the Circuitron auto reverse controller and the intermediate train detectors that allow stops along the way with a delay. The Bachmann PCC Street Car runs smoothly but only moderately slowly while the Spectrum trolley will run slower than a tie per second (plenty slow enough). My concerns about slow smooth running are for naught as both satisfy me.

My initial test was with the Spectrum Birney trolley with the DCC controller still in place and the little trolley was balky for starts. After I removed the DCC board and installed the supplied dummy plug the trolley seemed to perform better at slow speeds. But I did spend a couple of hours on each trolley letting it run continuously to break them in. I think that might have had something to do with the increased smoothness too.

Anyway there is NO pulse power in my future. All is well as is. What is remarkable to me (apparently a product of current motors having more poles than my trains of 50+ years ago) is the smoothness at slow speeds of both these trolleys but the Spectrum Birney is superior to the Bachmann PCC Street Car in that respect.

My idea was to kind of create my remembered environment of the 1950's with the Los Angeles Yellow  and Red cars (it does not have to be exact and the Birney is wrong for LA but it is red). I got so stoked after running the two trolleys that I ordered the Spectrum LA Lines Peter Witt street car.

Thanks again all for the help.

LDBennett

What trolleys will run on this HO track (Luna Track system) that has a radius of 10 inches (250mm)? The Bachmann trolleys require a 15 inch (350mm) radius track. Anyone using this track system that comes with tracks that appear to be in the roadway rather than on ties?

LDBennett

Hunt:

Review of the richg O-Scope photos reveals a frequency of about 16KHz and that is close enough to 22 Khz to be the same. The 150 Hz pulse power pak in the Thorne link is not even close and implementation of it might be problematical. If I attempt this pulse power scheme then it will be at the 16 to 22 KHz frequency, not 150 Hz.

Jim Banner:

Thank you for the good explanation. It kind of makes me believe that after I break-in my two trolleys I may be able to operate them smoothly without pulse power.

This exercise has been very educational for me and I appreciate all the good info provided by everyone. Knowing how DCC works takes away all the mystery of DCC. If I ever expand to a bigger layout (probably not in the future as I am space limited and age limited) I most certainly would implement DCC at the highest level as it is surely a neat system. For now DC control ((either pure DC or maybe (??) pulse control)) is all I need or want.

LDBennett

richg(Rich):

I hope you don't think I am arguing with you. I am just seeking information. So far you have offered very good info indeed and the O-Scope pictures were excellent. Thank you!

OK. The DCC motor controller is getting 12 volt pulses from virtually zero pulse width to 60 us with a period of the wave form of 60us. Got it. Thanks for the info.

That means the frequency is about 16KHz if the O-Scope pictures are correct. The Thorne link schematic seems to be operating at about 150 Hz. It also mixes the pulse with DC. Unless that makes the engines run smoother I don't understand why they do it that way. It appears that is a common theme in these older pulse DC power paks (??). I'd be interested  in seeing your schematic if it was just pure pulses.

I got my layout wired last night but have to set up the train detectors for the Auto Reverse before I can run the trolleys to see if they will run smoothly at slow speeds after they break in. I'll be busy all weekend so it will have to wait until next week.

Again, thank you. I really appreciate your efforts.

LDBennett  (Lynn Bennett)

richg:

Help me out here as I am not familiar with power paks by name.

Are you monitoring the DCC decoder controller for the motor as controlled by the NCE Power Cab? Is this the power form the engine motor sees?

If so then the motor sees variable pulse widths from virtually zero to 60us where the period is 60 us (??).

Does this result in very slow smooth engine operation?

The power pak you made years ago was straight pulse power with no DC mixed in and it gave smooth slow speed operation? Do you remember the period of the wave form? Was it about the same as the o-scope pictures? Do you happen to still have the schematic of the power pak or a link to where it might be found? I understand you added flywheels and low gearing but did you happen to test the setup without the mechanical changes? Was it smooth at low speeds?

Thanks,

LDBennett

Doneldon:

There is a difference between pulse width and waveform period. Pulse width is what is varied in DCC and apparently the repeat or period for nearly full throttle and small throttle is the same. Look at the O-scope pictures by richg. Note that indeed the pulse width changes from 10us to 30us to 40us while the period of the waveform is every 60 us. That is, the pulse repeats every 60 us regardless of the pulse width. The pulse voltage is always about 12+ volts DC. This is as I expected. The frequency is a bit higher than I would have guessed.

I'm a retired electronics (digital design) engineer and figuring how things work is part of engineering. I decided to figure out how DCC worked. After studying it some I realize that the decoder probably makes equal period pulse trains of varing pulse width. Was that the key to smooth slow speed operation? That is why I visited here to see if anyone here knew. A key factor is the waveforms period or frequency. All of this is doable with a minimum of parts  and I have the expertise.

My little layout is a straight section of single rail. It is a point to point city scene. I most certainly don't need DCC with all its computerized complexity. All I want is smooth slow speed operation of one trolley at a time. I have two trolleys, one with DCC and one without. The cost to use DCC would be pretty high to only get smooth slow speed operation. I know that using a pulse power will smooth out the operation from my own experience over 50 years ago. I am just trying to see if anyone else has experience using just pulse power without the mixing of DC with it as apparently several DC power paks do and determine what the period/ frequency of the waveform is.

This is not plan A (straight DC operation from a little Bachmann Power Pak) but plan B if the running of the trolleys is not smooth enough for me. I am not at the point where it is clear plan A will fail. But it does not hurt to research alternatives just in case.

LDBennett

My thoughts were to emulate the DCC motor controller in the DCC trains.

According to my reading the DCC decoder drives the motor. The diagrams indicate a constant period of the wave form (frequency) with a pulse width controlled by the decoder to match the speed command from the train cab controller/throttle. At small throttle settings the period of the wave form appears to be the same as that at nearly full throttle. When at full throttle the pulses disappears and all that is left is pure DC. But the period of the pulse train appears to be constant at all other throttle settings. There appears to be NO pure DC mixed with the pulses. What is that period?

The stuff I read does not show the DCC decoder/controller mixing pure DC with the pulse as so many of the DC pulse power paks appear to do.

All I am after is smoother slow speed operation and perhaps slow speeds not attainable with a common variable voltage power pak/throttle. Does it take the mixed pure DC with a variable pulse to attain that? or will just a variable pulse width, constant voltage, no pure DC mixed in version do the job better or as well???

Again this is just an mental exercise at this point as my layout is not yet far along enough to be able to run the trolleys for any length of time to even be able to break them in. I have run them to be assured the track has no shorts and the minimum speed was not to my liking but both trolleys are brand new and not broken in. This exercise is Plan B if I can not get the smooth low speed operation I desire after the trolleys motor are thoroughly broken in. I am days from finishing the Auto Reverse wiring and being able to run the trolleys point to point continuously to allow their motors to break-in. But I want to consider Plan B now, just in case.

Thanks to all those that offered help so far.

LDBennett

OK. So the "pulse power" is not a variable pulse width at full voltage but a combination of DC and a pulse riding on the DC.

I would think just a variable pulse width at full DC voltage would do fine IF the frequency was high enough so the engine (or trolley in my case) did not surge with every pulses such that you could see the surging. What frequency would it take to achieve that? Anyone tried?
RICHG, is that what you made years ago with the 555 IC?

Some 50+ years ago I added a "slow switch" to my layout that gave a 50% duty cycle of DC (kind of) and it did indeed improve the slow running. I did it by half wave rectifying the 60 Hz AC then provided the resultant half wave rectified  variable DC to the track. I was thinking that full voltage variable pulse width DC might do a better job. The question is what frequency works to keep the action of the trolley smooth and slow? The variable full voltage pulse width  appears to be what DCC does(). What frequency to they use?

In my situation there is no load to speak of as it is just a single trolley. I want it to go slowly at scale trolley speed. Slow speed operation of a DC motor is always hard to achieve without surging. Can the system I described make the motion of the trolley surge free or virtually?

Maybe I just have to experiment?

LDBennett

Thanks to the links given here I pretty much understand DCC. But I have another question.

When the motor controller part of the decoded follows the directions of the cab controller for speed and makes up a variable pulse width pulse train to run the motor to control the speed, at what frequency does it do it at?

Does this variable pulse width speed control really give and allow better slow speed performance?

As a mental exercise I wondered if I could get better and more realistic slow speeds with a variable pulse width voltage to the track of my non-DCC point to point trolley. I might consider coming up with an auxiliary circuit to do that if I knew at what frequency the action of the pulses on the HO locomotion would look smooth.

I also wondered if anyone made such a power pak/throttle that used a variable pulse width for speed control rather the variable  voltage. I do not need or want DCC.

Thanks:

LDBennett

CNE Runner:

Thank you for the insight but currently all I am doing is a point to point layout (18 inches wide by 8 feet long) with a single track that breaks at one end to the main track and two storage tracks, one each for the two trolleys I have. The most complicated control I have besides the Circuitron auto reverse module and the time delay module train detectors (two intermediate stops that have an adjustable delay of the stop period along with auto reversing at the end of the main track) is a electrical manual switch to turn off the appropriate storage siding for the trolley not in use.

The bottom line is DCC is not in my future. My question was whether to remove the DCC controller in one of the trolleys and replace it with the provided dummy plug, which has been answered. I have now done that.

I stumbled back into this model railroading when I inadvertently ordered an HO trolley instead of the N gage one I wanted for my grandson's little layout. Rather than return it I decided to make this trolley layout and so far I've enjoyed it. I am past the planning stage, have made the table, have nailed down the track, and wired as much as I can until the Circuitron modules arrive. I have a bunch of scenery supplies ordered and have all the buildings I want to use including four I built and a handful of other buildings that I bought assembled that have super detailing and weathering.

Its all been fun so far. I wonder how many 70 year olds start a model railroad project after having been away for about 55 years? I also have to help my 11 year old grandson with his N gage layout as it got destroyed by the cat after a family move.

Thanks for the help.

LDBennett