I am operating in DC
I am in the process of wiring lights on my control panel to show polarity on the different blocks on the layout.
The approach I am taking right now is to solder a wire on the track on one block (let's call it A) and solder the other wire on the adjoining block on the same side of track ( let's call that B). So when a train is in block A heading to block B and the light is on I know I need to change the polarity in block B.
Here is the problem I have come up with -
Using a multimeter I notice that the range of volts going through the track when operating trains is around 3 to maybe 11 or so. With that range an incadescent at 3 volts is hardly visible.
I originially used an LED but as you pros already would have known that if I am using only one rail it would only illuminate when there is a complete circuit in one direction, not the other.
Is there another approach that I can take to accomplish my goal?
Hope I explained properly my conundrum.
Thanks,
charles
Use two LED's.
Or a bi-color led.
rrebell Use two LED's.
I am looking for a solution that uses only 1 light.
josephbw Or a bi-color led.
You might use some kind of relay that is sensitive enough to trigger on low voltage but accept peak track voltage, and use it to switch a circuit that powers the LED from independent correct voltage.
There are inexpensive buck/boost cards -- one very recently referenced in another thread [Just Plug System] -- that I think can be set up to operate as constant-voltage supplies from variable DC source. That ought to be perfect to run a LED of choice. Someone will give you the information on these in better form than I can.
Note that a typical red/green LED inherently shows polarity: this is two light-emitting diode cores of opposite polarity in series. The diode functionality ensures only one of the two conducts when DC of either polarity is applied; the light-emitting functionality makes the diode in conduction light up. The problem here is that like a valve the color-coding shows absolute position rather than 'what it ought to be to match what you want'. Some of the people who have wired color-light signals will have answers to setting up the logic involved in showing an appropriate 'clear' signal for an approaching train-in-block, which could be used as an indicator for matching the 'approached' polarity correctly. But unless you're interested in signals, which I doubt, that would likely be too difficult or too expensive.
You're better off learning how to wire the blocks so the cab automatically determines the correct polarity, which is more complicated but well worth learning.
Would a bridge rectifier work with this?
York1 John
York1Would a bridge rectifier work with this?
The principal use of a bridge rectifier is to convert AC to full-wave DC, but everything he's doing is in DC already. And his LED inherently incorporates a diode, although at restricted voltage, so four of them correctly oriented would give directly visible evidence of which diodes are forward-conducting....
OvermodThere are inexpensive buck/boost cards
That is an idea! I have been just starting to play around with buck boosters as a prelude to do some lighting on the buildings on the layout.
If I can give a nod to RR_Mel, he has been super helpful giving me advice on lighting solutions based on the way he has his own layout wired.
I'm thinking a buckbooster set at 1.5 v and have it power a 1.5v incandescent then I wouldn't have to worry about blowing the incadescent and it would still be bright enough to see.
I am now wondering if I could wire it in such a way that one buck booster could drive multiple block wirings. Possible?????
AblebakercharlieSo when a train is in block A heading to block B and the light is on I know I need to change the polarity in block B.
isn't the polarity controlled by the throttle (except for reversing sections)?
if the same throttle is connected to both blocks, isn't rail-b connected to the same side of the throttle in both blocks?
or do you need a way to determine which throttle each block is connected to?
greg - Philadelphia & Reading / Reading
gregcisn't the polarity controlled by the throttle (except for reversing sections)?
Each block is wired to a DPDT center off switch so I can change the polarity or turn each block on or off. The throttle is for motion only.
When I am operating the trains and hitting all those DPDT switches like mad I sometimes forget what the polarity of a certain block is.
I am a visual person so if I have a light on my panel on the frontier between two blocks that can illuminate to tell me that I better change the polarity of the upcoming block or I'll get a short then I can keep the train merrily on its way.
OvermodWhat would you use it for? The principal use of a bridge rectifier is to convert AC to full-wave DC, but everything he's doing is in DC already. And his LED inherently incorporates a diode, although at restricted voltage, so four of them correctly oriented would give directly visible evidence of which diodes are forward-conducting....
When you have DC of unknown polarity, a bridge rectifier gives you DC of a known specific polarity out. To drive a single, non-bipolar, LED (he's already stated he only wants one light and one color) from power with unknown polarity, you'll need a rectifier in there somewhere.
The only problem with the rectifier is it will drop the volatge about 1.2 volts.
I guess I meant a diode bridge. You can buy them for just a couple of dollars.
https://en.wikipedia.org/wiki/Diode_bridge
A diode bridge is an arrangement of four diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input.
Overmod York1 Would a bridge rectifier work with this? What would you use it for? The principal use of a bridge rectifier is to convert AC to full-wave DC, but everything he's doing is in DC already. And his LED inherently incorporates a diode, although at restricted voltage, so four of them correctly oriented would give directly visible evidence of which diodes are forward-conducting....
York1 Would a bridge rectifier work with this?
What would you use it for?
Instead of alternating current, the setup would take DC current coming from either side and light the LED.
Ablebakercharlie gregc isn't the polarity controlled by the throttle (except for reversing sections)? Each block is wired to a DPDT center off switch so I can change the polarity or turn each block on or off. The throttle is for motion only. When I am operating the trains and hitting all those DPDT switches like mad I sometimes forget what the polarity of a certain block is.
gregc isn't the polarity controlled by the throttle (except for reversing sections)?
I don't understand why you wired this way. Could you please explain.
Is there a benefit over wiring the layout in the typical way most of the rest of us use?
You also reference "trains", in plural. But you also refer to "throttle" in the singular. I am not seeing how you run multiple trains on one throttle.
Ed
York1 I guess I meant a diode bridge. You can buy them for just a couple of dollars. https://en.wikipedia.org/wiki/Diode_bridge A diode bridge is an arrangement of four diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input.
You were right the first time as well, a bridge rectifier is just a diode bridge in one package.
AblebakercharlieThat is an idea! I have been just starting to play around with buck boosters as a prelude to do some lighting on the buildings on the layout.
A buck/boost converter should work. One problem is you would have to feed it with DC of a known polarity so you would have to have a bridge rectifier circiut. The bridge rectifier would drop the voltage about 1.2 volts, so the converter would have to turn on around 1.8 v. It may be hard to find one that turns on that low but still handles the maximum voltage (there are buck/boost converters that don't have a polarity requirement, but that just means they have the rectifier on board and they will have a higher minimum input voltage to compensate).
The easiest circuit would just be a bridge rectifier feeding an LED, but again, you would have the 1.2 v drop, so the LED would have to turn on around 1.8 v. Some red LEDs do have a 1.8v forward voltage, but you would also have a large enough resistor to protect it against the maximum voltage and once you add that it may not be visible at the lower end.
The best way I can think of off hand would be to use an optocoupler (actually a pair of them or a single AC input optocoupler to handle the unknown polarity) and separate power source to drive the LED. The circuit gets a little more complicated, but it could turn on very bright at a low volatge and little variation in brightness throught the range.
AblebakercharlieEach block is wired to a DPDT center off switch so I can change the polarity or turn each block on or off. The throttle is for motion only.
I have never seen a layout wired that way, also don't understand why you would want it that way, since it causes the very problem you are trying to solve which the "normal" method avoids.
I guess I don't understand why its a problem, if the switches control the polarity, wouldn't the handle of the switch indicate which polarity the track was assigned?
It seems sort of redundant to put a light over a switch to tell you which way the switch is thrown when the handle of the switch would indicate the same thing.
Dave H. Painted side goes up. My website : wnbranch.com
AblebakercharlieWhen I am operating the trains and hitting all those DPDT switches like mad I sometimes forget what the polarity of a certain block is.
I'm in agreement with Greg here. Just why do you need a reversing switch on each block and not in the throttle?
Kalmbach Diagram
There's no reason to have reversing switches at 1, 2, 3, 4, or 5.
The big downside to "bridging" the gap on each rail is that whatever you bridge it with will allow some current to pass.
So if you have block 1 energized and block 2 turned off with your center-off switch, if there is a locomotive in block 2 it will be drawing current through your "lamp/diode" indicator.
A diode will allow "full" current (up to the rating of the diode) to pass in one direction which would negate any circuit interruption provided by your block switch.
If you have two diodes, "back-to-back" bridging the gap between blocks you negate the reason for having a gap in the first place.
Is your layout wired for common rail cab control?
https://www.trains.com/mrr/how-to/build-model-railroad/how-to-wire-a-layout-for-two-train-operation/
Good Luck, Ed
Never mind - I missread some replies.
AblebakercharlieI looked for a bi-color LED where both colors are the same but could not find one. Is there an LED with only one color but the current can travel in both directions and illuminate the LED?
...so, to make one, you carefully file two packaged "LED"s down so that most of the package on one side is removed, and then cement them together (be sure they're opposite polarity as needed when joined). Join or solder the leads or pads. Then use clear epoxy or similar material to cast a lens around them if needed.
There have been posts here about reducing LED size to close to the actual device size (which is tiny even in older LEDs) for use in scale signal heads -- the 'community search' should find some.
I would suggest using a bridge rectifier, four Schottky diodes (1N5818). Voltage drop through a Schottky diode is about half of a regular diode.Arrange the bridge between the two adjoining rails with the output going to an LED of your choice with this in series.
http://www.hansenhobbies.com/products/lighting/electronics/led_cl_10/I have two of these working on my layout at a wye and loop. It works OK at 3 volts on DC and also on DCC. I run dual mode, DC or DCC on my layout. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
AblebakercharlieEach block is wired to a DPDT center off switch so I can change the polarity or turn each block on or off.
shouldn't the switch select one of two throttles?
if you don' thave two throttles, why wire them as reversing switches?
Hello All,
I have been reading and re-reading the OPs posts.
7j43kI don't understand why you wired this way. Could you please explain(?) Is there a benefit over wiring the layout in the typical way most of the rest of us use? You also reference "trains", in plural. But you also refer to "throttle" in the singular. I am not seeing how you run multiple trains on one throttle.
From my understanding of the OPs wiring and their comment...
It seems that they are not using "Common Rail" wiring.
They seem to have come up with a non-standard, Franken-bashed method of direction control based on a single cab, and DPDT center off switches, using the switches to control direction rather than the direction controller on the single cab.
When installing the Atlas Block Selectors the direction switch on the cabs are used.
If using the Atlas Controllers they do have direction switches built-in to them and the direction switches on the cabs are not use.
Perhaps this is where the OP got the idea of not using the direction switch on the cab.
dehusmanI have never seen a layout wired that way, also don't understand why you would want it that way, since it causes the very problem you are trying to solve which the "normal" method avoids.
Using commercially available DC circuit controllers and block selectors, even if only using one cab for motion, would simplify the OPs delima.
dehusmanI guess I don't understand why its a problem, if the switches control the polarity, wouldn't the handle of the switch indicate(s) which polarity the track was assigned? It seems sort of redundant to put a light over a switch to tell you which way the switch is thrown when the handle of the switch would indicate the same thing.
Every circuit I have worked with has a "logic" to it.
It seems the OPs "logic" has reached its inevitable dead-end with this circuit configuration.
The solution they are seeking is more complex than the problem they have created.
The OP might consider doing some research into "traditional" common-rail DC block wiring and utilize the Direction switch on the single cab rather than utilizing the DPDT C/O switch method currently in use.
If a DIY solution is sought by the OP then I suggest- -again- -the Complete Atlas Wiring Book, which shows schematics of their block controllers which can be replicated with DPDT C/O switches.
On the other hand, if I have misread the OPs posts/explanations, and they are using two (2) cabs then this...
Lastspikemike...has nothing to do with polarity.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
Sent you a PM - jjdamnit
AblebakercharlieSent you a PM - jjdamnit
i do hope jj will share the reason why able wired things as he did
gregc Ablebakercharlie Sent you a PM - jjdamnit i do hope jj will share the reason why able wired things as he did
Ablebakercharlie Sent you a PM - jjdamnit
I can see announcing that a PM has been sent to another forum member if someone truly needs to communicate something of a private, personal nature. But, otherwise, it seems a bit offensive to just go silent on the forum.
So, hopefully, the OP or the other guy in this instance will come back to publicly discuss the OP's issue.
Rich
Alton Junction
richhotrainUnfortunately, this seems to be the latest development on the forum. An OP starts a thread, gets lots of replies filled with suggestions and advise, then resorts to a PM with one guy.
I'll first start by saying that I really like this forum and have learned a lot from the different topics discussed here.
However, I'm going to have to disagree with you about the responses to my post here being suggestions and advice. From my viewpoint, most of them were along the lines of "you are doing it wrong" and "why on earth would you do it that way when everyone else is doing it another way". Being put on the defensive trying to explain my decisions didn't seem very worthwhile to pursue. A lot of these threads have gone south and I didn't want to be part of the problem. I had a question, I posted it, got an answer that I think will work and that's it.
But in the spirit of not being offensive I'll give it another go.
I am a DC operator. I decided to wire all the blocks as stand alone so there are no common wires on the layout. I have DPDT center off switches controling these blocks and I have one throttle powering all of them.
I have one throttle and yes, I sometimes run two trains at once although not for any extended period of time. An example - running a train around the mainline while running a train on a spur for a short distance. Not a big deal and I am certainly not claiming that one throttle can run a complex railroad. Far from it.
The idea of polarity indicator lights comes straight from p. 28 of my Andy Sperandeo's 1990 edition of Easy Model Railroad Wiring when he offers this technique as a visual solution to remembering to switch polarity on reverse loops. I wanted to explore that technique on the whole layout as it is easy to forget the polarity of a block when there are so many. Once again, a light is a nice visual cue instead of looking at the label on the switch.
Why the DPDT switches - remember, this is DC not DCC. I want the ability to have trains be able to go in different directions on different blocks at the same time. Also, with stand alone blocks, if there is a wiring issue I can easily isolate the problem and address it. Maybe a more experienced person wouldn't need this technique but for me I think it works nicely.
I PMed jjdamnit because he seemed like only one on this thread who was making an effort to see what I am trying to do. And also I have found his posts to be very sensible. Rich, I'll say I like your posts a lot too - they have been very helpful.
So once again, I apologize if my PM message was deemed offensive but then I found the tone of the reponses I was getting to this thread pretty off putting too.
Charles, thanks for that message. I have to say, I was looking for a word other than "offensive". I should have looked harder. I have followed this thread with interest, but I have not contributed since I am not a DC guy. So, when I saw your PM comment, I was disappointed that a solution to your issue might not become public. I do understand how you felt about the nature of the responses that you were getting.
Rich - No worries! Thanks for your response.