yankee flyer wrote: JeffThe scope helps.I see what you mean. One rail could be 10V + and the other 25 V + the loco wouldn't care unless it, or the track came into contact with the ground reference. As to my Atlas switch power. See what you think about this site. http://www.awrr.com/cdsupply.html This is the power supply I was going to use, but I could lower the voltage with a resister in series with the output. Lee
Jeff
The scope helps.I see what you mean. One rail could be 10V + and the other 25 V + the loco wouldn't care unless it, or the track came into contact with the ground reference.
As to my Atlas switch power. See what you think about this site. http://www.awrr.com/cdsupply.html This is the power supply I was going to use, but I could lower the voltage with a resister in series with the output.
Lee
It looks like a pretty typical capacitive discharge (CD) circuit. The base design is a 25VAC center tapped design with a full wave bridge and a capacitor. Thus the full charged voltage across C1 or C2 should be around 35 volts or so. What voltage are you trying to get to ? If you swapped the transformer our with a 12.6 VAC then the peak would be around 17-18V. You could also just use the center tap and one side of the 25VAC transformer and get the same thing, if you already have the parts.
The key on CD units is more about the current necessary to ensure that the switch coils fully throw than the supply voltage. This is where the capacitors come in because C2 is what stores the current necessary to provide the current rush draw by the coils. Most normal run of the mill power supplies aren't designed with this size of output capacitors or may have built in current limiting which will cause them not to be able to deliver large spikes of current. That's the only real difference between a normal power supply and a CD supply.
The other key value is the value of R2. It determines the short circuit current to the coils to keep them from buring up if a switch gets stuck. In this case a value of 390 ohms would limit current to around 90ma for the design shown or 45ma for a 12.6VAC transformer. The value of R1 is not critical.
Let me know if this helps or if you have other questions.
Engineer Jeff NS Nut Visit my layout at: http://www.thebinks.com/trains/
Phoebe Vet wrote: I agree 100% with what you just said. Now all you have to do to win me over to your side is show me that it, in fact, never reverses direction. I do not believe that is the case.
I agree 100% with what you just said. Now all you have to do to win me over to your side is show me that it, in fact, never reverses direction.
I do not believe that is the case.
It simply depends upon your point of reference. To a common reference point unipolar never changes direction but bipolar will. For the purposes of DCC it always will but this is because we are dealing with a differential signal between the two rails so a common reference point doesn't exist unless we talk about a single rail. So the sum of the two rail signals creates a equal and opposite differential that causes the rails to change polarity with respect to each other but an individual rail will not change polarity (with unipolar encoding) without the help of the other rail being 180 degrees out of phase. Again my whole point with the initial comment was that simply calling DCC an AC signal can be misleading depending upon the context of the conversation. For things like how to rectify out the DC component with a standard full wave bridge rectifier or similar, it will act very much like AC. For things like bit encoding and receiving and similar it will not.
Dave
Lackawanna Route of the Phoebe Snow
Phoebe Vet wrote: From the dictionary:Alternating current: An alternating current (AC) is an electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant. The usual waveform of an AC power circuit is a sine wave, as this results in the most efficient transmission of energy. However in certain applications different waveforms are used, such as triangular or square waves.What is so difficult?The direction of current flow changes cyclically. It does not "RESEMBLE AC". It is not "IN SOME WAYS SIMILAR TO AC", it IS AC.
From the dictionary:
Alternating current: An alternating current (AC) is an electrical current whose magnitude and direction vary cyclically, as opposed to direct current, whose direction remains constant. The usual waveform of an AC power circuit is a sine wave, as this results in the most efficient transmission of energy. However in certain applications different waveforms are used, such as triangular or square waves.
What is so difficult?
The direction of current flow changes cyclically. It does not "RESEMBLE AC". It is not "IN SOME WAYS SIMILAR TO AC", it IS AC.
Technically unipolar encoding does not change direction. It is on/off in the same direction. Bipolar encoding changes direction. Of course all of this is based upon the reference point being used. For example, a sinewave waveform offset on a DC reference that is higher than the peak of the sinewave will look like AC but never cross the reference point and thus will never change direction. This is exactly how AM radio works except the DC offset is a higher frequency carrier signal.
Rotoranch Hello
Over the year that I have been MR ing I'm sure that at least four have melted. I admit one or two have been my fault, leaning over the panel to reach something or possible laying something on them. I have taking a couple of the Atlas slide switches apart, they look perfect. Maybe they just don't rebound after being pushed? Anyway I was hoping to limit the power pulse to less than a second like atlas reccomends. Up untill this point I have been using a Lionel transformer that I measured at 8V to15V AC output.
The circut I'm looking at is at http://www.awrr.com/cdsupply.html by Fred Horne, anyone care to comment?
Happy railroading
Yankee Flyer...you're burning switch macine motors?
Again, what Atlas control switches are you using?
It has to be something getting set on the switches, or using the wrong switch.
I've only cooked 2 switch machine motors that I can recall since 1964. OK...3, counting one that cooked on The Kid's N scale layout. One each AHM, Lifelike and Atlas.
Since then, I've had 2 bad control panel switches. One Atlas quit many years ago, and I lost a Lifelike switch a few weeks ago. They didn't lock on, just quit working, (open circuit).
Rotor
Jake: How often does the train go by? Elwood: So often you won't even notice ...
In DCC there is no reference, there are just the two rails. Neither has a claim to being a 'zero' reference, they only change with respect to each other. So there is nothing other than the differential signal. I wouldn't call it AC, but in many respects (especially if you are hooking an LED to it) it is certainly more like AC than DC. But I would say that Engineer Jeff's description is technically the most accurate. (Of course also being an Engineer Jeff, that's an easy stance to take!)
Jeff But it's a dry heat!
yankee flyer wrote: Johnny_reb and all who posted thanks.As to your question, fortunately my train and honey do's are the only pressing items. I'm retired.My MOW light car is on hold until I get the Atlas dual coil motor power fixed so that I don't burn up the motors. Some of the meltdown may have occurred when I leaned over the panel to work. But there has to be other causes - sticking switches or something. I built the 12 volt power supply, but it won't throw two turnouts at a time. Someone referred me to Tom Horn's capacitor discharge circuit.It's a 35 Volt pulse. So I bought the parts, and that is my next project. Some of my E-tech skills are trying to come back. Back in the stone age I spent quite a bit of time in front of an oscilloscope, so I can visualize a square wave. Is the DCC power 15 volts peak to peak, or 30? How is a digital signal transmitted? Lee
Johnny_reb and all who posted thanks.
As to your question, fortunately my train and honey do's are the only pressing items. I'm retired.
My MOW light car is on hold until I get the Atlas dual coil motor power fixed so that I don't burn up the motors. Some of the meltdown may have occurred when I leaned over the panel to work. But there has to be other causes - sticking switches or something. I built the 12 volt power supply, but it won't throw two turnouts at a time. Someone referred me to Tom Horn's capacitor discharge circuit.It's a 35 Volt pulse. So I bought the parts, and that is my next project. Some of my E-tech skills are trying to come back. Back in the stone age I spent quite a bit of time in front of an oscilloscope, so I can visualize a square wave. Is the DCC power 15 volts peak to peak, or 30? How is a digital signal transmitted?
The absolute maximum is 22 volts. The recommended voltages are:
N scale - 12vHO/S/O scale - 15vLarge scale - 18v
Here's an oscope image of my HO scale DCC system output signal:
THANKS Rotor - eventually I'll give this a try and report back how easy/hard etc it was...
Phoebe Vet wrote: "could have just as easily been " is not the same as "is".A wave that is first positive and then negative in polarity is an Alternating Current. It is you who is playing confusing games with terminology.I am aware that many digital signals are pulsing DC and that pulsing DC would not have permitted DC engines to reverse direction. That is why they use zero stretching on one side of the alternating waveform to control the DC engine. DC engines run slower on a DCC track because they are only getting half the voltage. They get only the positive or only the negative for a long enough period of time for the engine to react. The rest of the time, the direction of the current is reversing too fast for the motor to react, hence the annoying buzz. I was doing digital signal analysis as far back as 1965.Put an oscilloscope across the rails of your track and look at the signal. It's square wave AC. It is ALTERNATING between positive and negative.If you choose to call that positive DC and negative DC on the same signal, that's fine, but don't complain that others call it what it is. The people calling it AC are not wrong. Since electronic devises don't speak english, they will react to what they see. And they see AC.You know, like calling a man a "detainee" does not alter the fact that he is a "prisoner". Changing the name does not change the facts. I believe that you are confusing a description of the waveform (a variable timed square wave as opposed to a sine wave) with the AC vs DC argument.
"could have just as easily been " is not the same as "is".
A wave that is first positive and then negative in polarity is an Alternating Current. It is you who is playing confusing games with terminology.
I am aware that many digital signals are pulsing DC and that pulsing DC would not have permitted DC engines to reverse direction. That is why they use zero stretching on one side of the alternating waveform to control the DC engine. DC engines run slower on a DCC track because they are only getting half the voltage. They get only the positive or only the negative for a long enough period of time for the engine to react. The rest of the time, the direction of the current is reversing too fast for the motor to react, hence the annoying buzz. I was doing digital signal analysis as far back as 1965.
Put an oscilloscope across the rails of your track and look at the signal. It's square wave AC. It is ALTERNATING between positive and negative.
If you choose to call that positive DC and negative DC on the same signal, that's fine, but don't complain that others call it what it is. The people calling it AC are not wrong. Since electronic devises don't speak english, they will react to what they see. And they see AC.
You know, like calling a man a "detainee" does not alter the fact that he is a "prisoner". Changing the name does not change the facts. I believe that you are confusing a description of the waveform (a variable timed square wave as opposed to a sine wave) with the AC vs DC argument.
I am not going to get into a huge debate on this. I have an oscilloscope and have looked at the pulses on each rail. I also have an EE degree and have designed networks and digital transmission systems, including differential pulse systems like this.
I did a little more digging today on the NMRA website. Looking in RP9.1.2 section 2.3
http://www.nmra.org/standards/DCC/standards_rps/RP-912.pdf
the recommended practice shows that either unipolar or bipolar encoding is supported as long as the differential is maintained to keep the DC component constant. If not, locomotives would speed up and slow down as the symmetry of the pulse stream changed since this would cause a fluctuation in the DC component. I thought I had read previously in the NMRA specs that only unipolar was supported. They are cheaper to manufacture but bipolar can generally be transmitted over a greater distance (all things being equal).
If you want to make the case that any system using bipolar encoding is AC that is fine. They do have a zero crossing point, which is one characteristic of AC. A unipolar system does not have a zero crossing point and instead maintains a supply and common voltage reference point that are 180 degrees out of phase but neither rail would ever cross zero.
There isn't any way to know which method a DCC manufacturer is using without looking at the output on an oscilloscope.
yankee flyer wrote: DonActually my rail MOW is a Bachman, silver, with a cabin, tool chests and the "flood" light. But I was testing an LED. Talking about dumb, I knew LED stood for light emiting diode. I just was not thinking polarity.Johnny_rebI am getting really aggravated with these Atlas slide switches. the package says use AC current. I tried a toy train transformer at 8V to 12V AC and got melted motors. I tried a small 12V DC power supply and got melted motors. I think I'm going to rip out all the Atlas switches and replace with raido shack push buttons, one for each direction. It must be the switches. Also I am experimenting with an auto light bulb in series with the switch panel so I will know when current is flowing. That will tell me if a button is stuck. I did buy the resister and capacitor in the diagram you posted but I dont understand how it limits current flow.Lee Watching Freezing rain.
Don
Actually my rail MOW is a Bachman, silver, with a cabin, tool chests and the "flood" light. But I was testing an LED. Talking about dumb, I knew LED stood for light emiting diode. I just was not thinking polarity.
Johnny_reb
I am getting really aggravated with these Atlas slide switches. the package says use AC current. I tried a toy train transformer at 8V to 12V AC and got melted motors. I tried a small 12V DC power supply and got melted motors. I think I'm going to rip out all the Atlas switches and replace with raido shack push buttons, one for each direction. It must be the switches. Also I am experimenting with an auto light bulb in series with the switch panel so I will know when current is flowing. That will tell me if a button is stuck. I did buy the resister and capacitor in the diagram you posted but I dont understand how it limits current flow.
Lee Watching Freezing rain.
Lee, it does sound like your switches are sticking. Adding a light into the wiring will let you know if they are sticking. I myself plan to make all my turnout work with ground throws.
Just a thought here, does anyone else have access to your layout while you are at work? If so they may not understand how the switching system works.
Johnnny_reb Once a word is spoken it can not be unspoken!
My Train Page My Photobucket Page My YouTube Channel
JWBDolphins wrote: I too have a Bachmann MOW spotlight car and a DCC Zephyr. It is nice that the light is on full brightness all the time, but I did wonder about the bulbs longevity. I was also thinking about installing a mobile DCC decoder in it so that I could turn it on or off remotely and in fact went so far as to buy the decoder.What I haven't had is the time to mess with it. I've searched online to see if anyone has done this before and posted pictures/instructions - so far I've found nothing. It did strike me that this might be massive overkill too! But I like tinkering with things and will eventually give this a shot.Has anyone done this and have any tips? It looks like the MOW car has all-wheel pickup, which is good. I figured I could hide the decoder in the cabin of the car. My two other thoughts were 1) replacing the bulb with an LED or maybe 3 (again, has anyone done this already?). The advantage of the DCC decoder is that it will take care of the current polarization for the LEDs. Even if I don't replace the bulb, shouldn't the current rectifier that is built into the decoder reduce the current somewhat that goes to the bulb?, which will hopefully help it last longer. And 2), the decoder I chose has 4 functions on it - I was thinking of putting a micro slide switch under the car so I could select which decoder function number would turn on or off the spotlight. This way if I wanted to, I could set the decoder to the same number as one of my locos and have a selection of functions to choose from that wouldn't interfere with the loco.If anyone has modified this MOW car, I'd be curious to know any tips or suggestions. Maybe I'll take and post some pictures myself if I get around to this.Back to the original poster's question - I think its been answered. DCC will light the bulb at full power all the time - the bulb won't care which direction the DCC current is flowing.
I too have a Bachmann MOW spotlight car and a DCC Zephyr. It is nice that the light is on full brightness all the time, but I did wonder about the bulbs longevity. I was also thinking about installing a mobile DCC decoder in it so that I could turn it on or off remotely and in fact went so far as to buy the decoder.
What I haven't had is the time to mess with it. I've searched online to see if anyone has done this before and posted pictures/instructions - so far I've found nothing. It did strike me that this might be massive overkill too! But I like tinkering with things and will eventually give this a shot.
Has anyone done this and have any tips? It looks like the MOW car has all-wheel pickup, which is good. I figured I could hide the decoder in the cabin of the car. My two other thoughts were 1) replacing the bulb with an LED or maybe 3 (again, has anyone done this already?). The advantage of the DCC decoder is that it will take care of the current polarization for the LEDs. Even if I don't replace the bulb, shouldn't the current rectifier that is built into the decoder reduce the current somewhat that goes to the bulb?, which will hopefully help it last longer. And 2), the decoder I chose has 4 functions on it - I was thinking of putting a micro slide switch under the car so I could select which decoder function number would turn on or off the spotlight. This way if I wanted to, I could set the decoder to the same number as one of my locos and have a selection of functions to choose from that wouldn't interfere with the loco.
If anyone has modified this MOW car, I'd be curious to know any tips or suggestions. Maybe I'll take and post some pictures myself if I get around to this.
Back to the original poster's question - I think its been answered. DCC will light the bulb at full power all the time - the bulb won't care which direction the DCC current is flowing.
The answer to most of your questions is yes. With the decoder in the spotlight car, you wouldn't need a switch. The decoder would handle the switch. It wouldn't "interfere" with the loco, as all you will be using is the light circuit. You'd just need to set the function CV's as you want them.
The cabin would make a good place to hide the decoder.
One super white LED would make the light look like a carbon arc spot light. Should look great. One LED is all that will fit in the reflector correctly.
yankee flyer wrote: Johnny_reb I am getting really aggravated with these Atlas slide switches. the package says use AC current. I tried a toy train transformer at 8V to 12V AC and got melted motors. I tried a small 12V DC power supply and got melted motors. I think I'm going to rip out all the Atlas switches and replace with raido shack push buttons, one for each direction. It must be the switches. Also I am experimenting with an auto light bulb in series with the switch panel so I will know when current is flowing. That will tell me if a button is stuck. I did buy the resister and capacitor in the diagram you posted but I dont understand how it limits current flow.Lee Watching Freezing rain.
A switch is a switch. It has no idea if it's switching AC, DC, or DCC. It just opens and closes a circuit.
What motors are you melting? And which Atlas switches are you using?
Phoebe Vet wrote: jbinkley60 wrote: I really wish folks would stop saying that DCC is AC. In certain contexts it can be very misleading. The shape of the wave is irrelevant. When current flow alternates between positive and negative, that's AC. Why, what do you call it?
jbinkley60 wrote: I really wish folks would stop saying that DCC is AC. In certain contexts it can be very misleading.
I really wish folks would stop saying that DCC is AC. In certain contexts it can be very misleading.
The shape of the wave is irrelevant. When current flow alternates between positive and negative, that's AC. Why, what do you call it?
AC generally refers to a continuous function signal that is a complete waveform that traverses from a positive signal voltage, crosses the 0 volage axis point, goes to a negative peak and then back to to 0 voltage axis point.
DCC is a balanced DC differential pulse modulation system. What this means is that each lead (or rail) is a DC pulse stream that is 180 degrees out of phase with each other. Because they maintain this equal and opposite symmetry the DC component remains almost constant and thus can be rectified out to provide the power necessary to drive motors, lights etc. There is no zero crossing point with regrads to a common reference point, only to each other.
You are welcome to call this AC, if you'd like. It is just misleading in certain contexts and conversations. DCC could have just as easily been a unbalanced unipolar, not a differential design and there would be no zero crossing point. A bipolar design would have a zero crossing point but no DC component. The main reasons a differential scheme was chosen was to carry the DC component and to reduce noise.
Johnnny_reb:
That description was perfect, except for the 60 cycle reference. House current in the US is 60 cyycle, but AC describes alternating current at any cycle frequency.
Yankee Flyer:
I can speak vacume tube. It's the same principle. A diode has an anode and a cathode, just like a tube. If you add screens like tubes use to control flow, then it becomes a transistor. Flow is only one way. Four diodes combined in a bridge can convert AC to DC.
All:
Becarefull hooking diodes up. Like all solid state electronic deviced if they overheat, they will be destroyed.
Let me guess, you have the popular Bachmann Silver MOW car with crane? I have one too.
I believe it is a 12 Volt bulb. If you put it on a DCC track (typically 13->15V aternating current) then you will drastically shorten the life. I would see if you can put a resistor in there somehow.
~Don
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
yankee flyer wrote: Johnny_rebYou are not the only one confused, like I said my tech school was a long time ago (1956).I was an Airforce tech, repairing radar that put out 5 million watts of power,and we did it with vacuum tubes. I haven't done anything technical since 1960. I bought an LED and tried it on a 12V DC power supply, nothing, I tried it across the track and it lit up. It looks like I'm going to have to start "school" all over again. LeeWishing for, Blue Skys
You are not the only one confused, like I said my tech school was a long time ago (1956).
I was an Airforce tech, repairing radar that put out 5 million watts of power,and we did it with vacuum tubes. I haven't done anything technical since 1960. I bought an LED and tried it on a 12V DC power supply, nothing, I tried it across the track and it lit up. It looks like I'm going to have to start "school" all over again.
Wishing for, Blue Skys
Lee, I am sorry if I have misled you, but I was not confused. I was being sarcastic.
An "LED", like all diodes only works one way. A bi-color diode is two diodes in one case. A tri-color diode is three diodes in one case, so on and so forth.
Simply put a diode is a one way valve. In that it will let current pass only one way. So if you hookup the diode backwards it will not light. If this is the case just turn the diode (half-way) around and try it again.
As I do not make my living in electronics I will not try to explain the leads on an "LED". But all "Led's" that I know of use "DC" voltage. But will light up if hooked up to "AC" voltage because it changes polarity at 60 cycles a second, giving the "Led" the right polarity half of the time.
Now if one of the "electronic" guys will chime in here as they can explain it better then I.
Holy cow you mean that DCC is "AC"? I have just started reading up on DCC and already know that DCC is "AC" and that the "decoder" turns it back into "DC" before it sends it out to the motor or other accuracy's. It's no wonder that an "LED" meant for "DC" voltage is getting "HOT". This is "SO CONFUSING". Not!
tstage wrote: yankee flyer wrote: This forum is great.changing to an LED would be a very good first project of that sort I appreciate the suggestions.LeeAnd don't forget your resistor...Tom
yankee flyer wrote: This forum is great.changing to an LED would be a very good first project of that sort I appreciate the suggestions.Lee
This forum is great.
changing to an LED would be a very good first project of that sort I appreciate the suggestions.
And don't forget your resistor...
Tom
You may also want to put a diode in series with the resistor and LED too. LED's are not meant to be rectifiers, but they will do OK for a while. A 1N4001 will work. Connect it cathode-to-anode of your LED. It is not going to mater which lead goes to what rail as the track is now AC with your DCC system.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
yankee flyer wrote:This forum is great. changing to an LED would be a very good first project of that sort I appreciate the suggestions.Lee
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.