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The MTR-12T relay module can operate on AC (or DC) voltage.
The 4-channel relay module you show operates on 12V DC voltage. If you use a 12V DC wall-wart adapter which are about $2-3 on eBay (free shipping from Asia), you can perform the same insulated-rail triggering as your diagram shows.
I've never seen one but from the photo there appears to be a small capacitor on the MTR-12T that may provide a bit of chatter protection from intermittent wheel contact. You might hear the relay click and/or red-green lights flicker back and forth when a consist enters or leaves the insulated rail section.
The 4-channel relay module does not have that component so you may hear more chatter...but hard to say. You can add 25 cents of components to each relay channel to demote this chatter. I've posted hookup instructions to use these low-cost relay modules in previous OGR threads. So if you're interested I can dig them up - let me know what you actually have in-hand...and your interest/comfort-level messing with components/wiring so I can suggest something meaningful to you.
Stan,
If I could help explain a little about what Mike would like to do. I could help him with the standard signal bridge hookup, but here is where I got lost and recommended that he wave a flag for you
: "Hi John, what I am trying to do is have my bridge over 2 sets of tracks. If the train is going north bound I want the green light to say its clear, but show on the south bound on the same track red and occupied. "
Thanks John for jumping in!
Stan, as for my knowledge of this stuff it is very little. I do have a wall wart to use with the relay I have. I bought it about a year ago and forgot what for so I thought I could use it here. I can do little wiring and soldering but not to the point to build a board as of yet! LOL
John H posted:...If the train is going north bound I want the green light to say its clear, but show on the south bound on the same track red and occupied. "
Hmm. I'm a bit confused on what you're trying to do. Are you asking about a wiring scheme that can be applied to one track? In other words, ignore that you have 2 parallel tracks under the bridge and we're really talking about the wiring for one track with two signal heads - one head facing north and one facing south over that one track.
Your wiring diagram shows only 1 signal head per track. The diagram is also labeled "Unidirectional traffic" which again is not what I'm reading? 
Again, I may be misunderstanding but it sounds like you're describing a Bi-directional traffic application (on a single track) which is a bit more complex to wire up ... typically requiring two insulated rail sections per track with smarts to determine which direction the train is going to affect the two opposing signal heads as you describe. The wiring could then be duplicated for the 2nd parallel track.
Hi Stan, The diagram is from a post that I found on here from awhile back, looked like it would work if I just doubled it for 4 heads instead of just 2. I don't even know if this is protatipical or not, just thought it would be cool cause the manual states if you have one track with train travel in both directions you can install one head above the other and it shows the green light for incoming traffic and red light in the other direction.
mike g. posted:Hi Stan, The diagram is from a post that I found on here from awhile back, looked like it would work if I just doubled it for 4 heads instead of just 2. I don't even know if this is protatipical or not, just thought it would be cool cause the manual states if you have one track with train travel in both directions you can install one head above the other and it shows the green light for incoming traffic and red light in the other direction.
Then what problem are you trying to solve?
The answer to your initial question is "Yes." You can use the 12V DC 4-channel relay board with the additional of a 12V DC wall-wart to implement the wiring diagram as shown. As I said I can modify your wiring diagram to essentially erase the MTR-12T and insert the 4-channel relay module plus 12V DC wall-wart. But if that's not what you're trying to do then I won't bother.
The answer to the modified/revised question is "not enough information". I don't care if it's prototypical or something you dreamed up; just describe exactly what you want and let's see what it would take to get it done! Again, let's just talk about one track. Any "solution" can be duplicated for the 2nd parallel track.
So from what I gather you have a North facing and South facing signal. Do you envision one long insulated-rail section that spans both sides of this dual-facing signal? Apparently when a train passes through the signal only changes red facing a following train (stays green facing on oncoming train even though it would be a head-on collision?). When does the red turn back to green?
Hi Stan,
First off I want to thank you for taking the time out of your day to help me. I would like to use the 4 relay setup as I have that already and don't want to spend anymore money if I don't have to.
so here is what I don't know. I have 4 wires coming from 2 heads, I then have 2 wires coming up from the base of the Linoel 450 signal bridge and I am not sure how to wire them together.
I do envision a long insulated-rail if that is what I need to make this work, even thought there will not be 2 trains on the same rail at the same time, I would like the green light to come on for the incoming train and red for the other direction. When the train clears the insulated-rail area both turn green again. The reason I am thinking this way is because the layout will be setup with a reverse so the train can go either direction.
if this is not correct I am sorry. I am really trying to understand the signal thing!
Hi Stan, I hope I didn't push you over the edge!
mike g. posted:Hi Stan,
First off I want to thank you for taking the time out of your day to help me. I would like to use the 4 relay setup as I have that already and don't want to spend anymore money if I don't have to.
so here is what I don't know. I have 4 wires coming from 2 heads, I then have 2 wires coming up from the base of the Linoel 450 signal bridge and I am not sure how to wire them together.
I do envision a long insulated-rail if that is what I need to make this work, even thought there will not be 2 trains on the same rail at the same time, I would like the green light to come on for the incoming train and red for the other direction. When the train clears the insulated-rail area both turn green again. The reason I am thinking this way is because the layout will be setup with a reverse so the train can go either direction.
if this is not correct I am sorry. I am really trying to understand the signal thing!
Yep that's how the real deal works.... The only thing that's not prototypical is.. lets take one track only...If either the north bound or sound bound block are unoccupied both back to back signals are going to be green,,,
I'm sure there's a way to eliminate this or even have all the lights out until a train enters the block and then all signals light up. fun project.
Hi Greg, that is kind of what I working on, I would like both light in both directions to be green until a train approaches.
mike g. posted:Hi Stan, I hope I didn't push you over the edge!
It's on my list.
Obviously there are companies that sell signaling hardware systems, or one could design a logic circuit (requiring soldering and working with digital components and such), or use an Arduino controller board and write some software, and so on... but where's the fun in that?
I'd be looking for a no-soldering, no-programming, zero or minimal additional out-of-pocket solution using the low-cost relay module you already have.
You'll need two insulated track sections; one before the signal, the signal bridge itself in the middle, and another insulated track section after the signal.
South ===== I ===== North
The section south of the signal controls the southbound signal head and the section north of the signal controls the northbound signal head.
A northbound train sees only a green light but as he enters the insulated track section (the first block) before the signal, the opposing light turns red. As he passes under the signal bridge and onto the next block, the northbound signal will turn red as well (both directions will show red). The southbound signal will return to green as the end of the train clears the first block. And the northbound signal will return to green when the end of the train clears the second block. That's very prototypical operation.
Now you want to use your 4 channel relay board instead of the relays shown in the circuit diagram that you posted. I've got a similar relay board that operates on 5 volts with optoisolation. So mine is different than what you've got. What are the jumpers for (I see one for each channel) ? Does yours provide optoisolation (opto-couplers) ?
When it comes to the AC negative coming off the insulated rail, I get kinda confused. As long as your transformers are in phase (the U terminals tied together and the plugs all turned in the right direction), you can power the relays from an independent power source. For you, that would be your 12 volt wall wart which you will have to get in phase with your other transformer(s). But the wall wart puts out DC and the trains run on AC. This is where I get confused. Maybe Stan can clear this up for both of us.
Otherwise, I think you're on the right track. The circuit minus the second track looks fine.
As far as the wires are concerned, two wires from each of the signal heads would be one for the red light and one for the green light (we are talking light bulbs here and not LED's). These according to your circuit diagram are both common AC negative leads. The power lead is built into the signal bridge but has to get to each head somehow (probably thru the structure and may not be visible). Just test which of the remaining wires from the structure will turn on a light. Put a wire from the head to AC ground and a wire from the structure (I see a red one and a black one) to AC plus. Stick a label on each lead for future reference. We'll get you there a step at a time.
stan2004 posted:mike g. posted:Hi Stan, I hope I didn't push you over the edge!
It's on my list.
Obviously there are companies that sell signaling hardware systems, or one could design a logic circuit (requiring soldering and working with digital components and such), or use an Arduino controller board and write some software, and so on... but where's the fun in that?
I'd be looking for a no-soldering, no-programming, zero or minimal additional out-of-pocket solution using the low-cost relay module you already have.
Sounds great Stan, I am in no hurry. I have so many projects and maybe that's my problem, I jump around from one to the next and back again! LOL
Consolidated Leo posted:As far as the wires are concerned, two wires from each of the signal heads would be one for the red light and one for the green light (we are talking light bulbs here and not LED's). These according to your circuit diagram are both common AC negative leads. The power lead is built into the signal bridge but has to get to each head somehow (probably thru the structure and may not be visible). Just test which of the remaining wires from the structure will turn on a light. Put a wire from the head to AC ground and a wire from the structure (I see a red one and a black one) to AC plus. Stick a label on each lead for future reference. We'll get you there a step at a time.
From what I can tell the bridge it self is a ground point for the lights. All the red wires you see hanging down are the power leads off of the LED's. As the bridge is concerned I am not sure what series to wire the power leads. Such as one red with one green or both reds together and both green's together. There are the Red and Black wire that come up from the base for power hook up. one for each head.
Mike,
Whoa! Slow down! The best way to approach a problem with several unknowns is to break it into smaller pieces. The more things that you are sure about, the less trouble you will have. You can't just start wiring up the complete circuit without doing some experimentation first.
Let's start by working on the signal bridge. Are the signals LED's or light bulbs? I assumed that the original 450 signal bridge would come with light bulbs. Did someone change them to LED's? If that's true, then we'll have to be concerned with polarity and a series resistor to limit the current.
If you stay with me and forget about cross connecting red and green lights, I'll explain more.
-- Leo
Hi Leo, thanks for your time. The light are LED's that I have put in, they are 5mm Red and Green Led's rated for v5,6v,9v DC 12V DC 20 cm.
I have used them for many projects I have done.
That's good.
I've been looking over the old instruction sheets for the 450 signal bridge where they tell you how to make connections on the base for different combinations of lights. Forget all about that. We don't have to connect lights together at all. The relays and insulated rails will handle all of that. But hold on, let's just figure out the LED wiring.
Did you keep track of which side of the LED's you hooked the wires to coming out of the signal heads? You said that you've used this type before. Are you able to get them to light up in isolation? A 9 volt battery should work. I'm not sure if they need a series resistor but I would think so (about 500 ohms).
Eventually, we will connect the leads from the signal heads to the terminals on your relay board but lets figure out which wire is which first.
Hi Leo, They come prewired, with a resistor in them already, I can hook them to my wall wart and they all light up. So from what your saying I am going to need 4 hot wires coming all the way down threw the base?
Mike,
Earlier you said: "so here is what I don't know. I have 4 wires coming from 2 heads, I then have 2 wires coming up from the base of the Linoel 450 signal bridge and I am not sure how to wire them together."
Does this mean that each signal head has 2 wires for a RED LED and 2 wires for a GREEN LED? This means there are 4 wires from each signal head. Is that right?
If that is true, the wires in the signal bridge structure are not connected to anything since you have rewired it with your LEDs and we can forget about the black and red wires in the base.
First, are there 4 wires coming from each signal head?
-- Leo
Hi Leo, there are 4 wires from each head, 2 black and 2 red. The black ones are grounded under the signal heads. All I have left hanging are 8 power leads for the 4 heads.
Gotcha Mike,
If you connect a power lead and the black wire in the base to your power source, does that light up an LED? I'm thinking that since you've set up your LEDs with a common ground, being the structure, maybe one of those base wires is also setup as a ground.
Hey Leo, before I cut the wires to the signal heads to paint them, the black wire went to power the green light bulb, and the red wire went to power the red bulb. Yes if I put power to either the red or black wire in the base and then touch it to any of the power wires coming off the signal heads the light will light.
That's good, I think.
But wait a minute. Didn't you say you connected both the two black wires to the metal structure of the signal bridge as a common ground? And now you say that the black wire is power for the GREEN LED? The black wires connected to your LEDs can not be both power and ground. LEDs have polarity and you can't mix them together. But if you can assure me that by your tests you were able to light up both RED and GREEN LEDs, without changing the power connections (positive to red wires, negative to the base wires), then we can move on.
Yes we will need all 8 power leads to go to your relay module. The 2 wires from each signal head will connect to 1 of the 4 relays so that the aspect will display either RED or GREEN.
Painting wires is always a lot of fun. I'll get back to you tomorrow with more of the plan. I need to do some experimentation of my own to find out how my relay board acts when connected to AC negative of the isolated rail.
I added qty 4 capacitors (47uF, 35V) which are about 10 cents each. So that's added to your 12v 4-channel relay board which I see is just over $3. You apparently already have a 12V DC wall-wart.
This example uses 4-relays of an 8-relay 12V board as that's what I had handy. As Leo suggests you need 2 adjacent insulated sections to get bi-directional behavior.
I cut some insulated sections into a piece of track and attached the two orange wires as the triggers to the circuit. The small white prototyping board holds a two pairs of Red/Green LEDs and resistors. It's kind of hard to see the green LEDs but they are right above the red ones. And here it is in action.
The "privacy screen" is simply to block the distracting LEDs on the relay board; there's a red power LED that's always on, and a red LED for each relay which turns on when active.
So with no train present, both heads are green. Coming from one direction, one of the signal heads turns red and stays red until the train exits both sections. Coming from the other direction, the other signal head turns red and stays red until the train exits both sections.
Sorry, but I gave up trying to get my head around north-bound, south-bound, what's prototypical, what's just-for-fun, etc. I made something which I thought was interesting. Take it or leave it!
If you want to know exactly how to wire THIS SPECIFIC implementation I will draw it up based on the 4-channel relay board shown above. The basic idea is as follows. Each signal head needs an SPDT or 2-output relay to drive red or green. To perform bi-directional behavior you need a 2nd relay for that signal head to act as a "lockout" to disable the red/green toggling from occurring if the train entered from the other side. That's why there are 4 relays for two signal heads rather than just 2.
Hi Stan, first off thank you! From what I see I will have to buy another 4 relay board and 8 capacitors. You have figured out what I was looking for. If that is something you could draw up that would be great and when I get the other relay set and capacitors then I can start putting thing together.
Stan, you really go that extra mile, even prototyping the thing! 
Consolidated Leo posted:That's good, I think.
But wait a minute. Didn't you say you connected both the two black wires to the metal structure of the signal bridge as a common ground? And now you say that the black wire is power for the GREEN LED? The black wires connected to your LEDs can not be both power and ground. LEDs have polarity and you can't mix them together. But if you can assure me that by your tests you were able to light up both RED and GREEN LEDs, without changing the power connections (positive to red wires, negative to the base wires), then we can move on.
Yes we will need all 8 power leads to go to your relay module. The 2 wires from each signal head will connect to 1 of the 4 relays so that the aspect will display either RED or GREEN.
Painting wires is always a lot of fun. I'll get back to you tomorrow with more of the plan. I need to do some experimentation of my own to find out how my relay board acts when connected to AC negative of the isolated rail.
Leo, I am sorry to confuse you, the black wires coming from the signal heads are grounded out to the bridge it self. Lionel has a red and a black wire coming from the base and both were used for power in the old light bulbs as the bridge is the ground it self.
Here you go. If I understand your LED wiring (thanks to Leo for breaking up the problem into smaller pieces) all the "-" wires to the individual LEDs are tied together so you apply "+" 12V DC to an individual wire to illuminate one of the 8 LEDs (4 signal heads, red/green per head) with resistors already "built-in". This image is a cut-and-paste edit on a previous posting but I think it shows the complete wiring.
Turns out you only need 2 capacitors for each 4-channel relay board so I just saved you 20 cents! 
Well, I guess you have to buy 10 pieces so maybe not. LOL.
In case it's not obvious, you simply duplicate the diagram for the parallel track....except you can use the same 12V DC wall-wart.
Wow! That is excellent Stan! I've not been able to follow the logic of what you've done here but it works the way Mike specified earlier and that's what counts. Great job!
Mike, sorry about the confusion earlier. I was thinking about the signal heads and you were telling me about the wires in the base. I realize my mistake and find it somewhat amusing. Don't paint any more wires!
It looks like Stan has come up with the solution that you were looking for. I'm so glad to have worked with you on this project. I'll be around.
Someday I'll understand how you can run DC through the same conductor as AC voltage but right now I'm uncertain. I get the idea of isolating completed circuits but that whole concept is new to me. Most electrical discussions center around whether it's okay to run AC and DC through the same conduit (side by side) without induction causing trouble. Maybe it's different at low voltage. Anyway it's a neat trick if it works.
For myself, I'm more inclined to look into GunRunnerJohn's design for a track isolation relay circuit. My first impulse is to run AC negative through a bridge rectifier to get to DC as soon as possible. I'll be watching his development efforts with great interest. It's about time we 3 rail folks have a cheap and easy answer to block detection.
Hi Stan, thank you so very much, that is just what I was looking for! The way you drew it up makes it looks so simple, and that is great for a slow guy like me when it comes to electrical.
Leo, between you and Stan you were both great help!, I also like you don't understand a lot of this and that is why I am so glad to have people like Stan, Yourself and GunRunnerJohn, along with many others like John H, GGG, RTR. so many great minds here its wonderful!
I also will be looking to get some of John's isolation boards.
Let use know how it works out!
Note that if you already have the relay-board and 12V DC wall-wart you can wire it all up without the capacitors - just provision room/space to insert them when they arrive. You might see flickering LED behavior without the capacitors but it should behave - nothing will be damaged or whatever without the capacitors installed. Also, the that exact value is not critical should you happen to have other similar valued capacitors.
Thanks Stan, I can wire up one set of heads, but have to wait for another relay board of 4, but then again I might just buy the 8 relay setup and do it all at once.
Hi Stan, I know you have done so much for me and I hate to ask you , but do you have the links to the 8 relay and capasitore so I don't buy the wrong thing?
If you go for the 8 relay module, make sure it offers "low" level (or selectable "low" or "high" level) triggering.
Also, you probably noticed that, on eBay anyway, there are fewer choices for modules that have screw-terminal inputs. All the relay outputs are screw-terminals. Those square-pin input headers require special crimped-wire connectors which, while not expensive, are something most guys don't have lying around.
Lets give this a try. The 12 volt common power connects to the outside rail so that the wheels will act as a switch to complete the circuit with the insulated rail sections. The 12 volt power feeds the relay board at DC plus and minus. The 12 volt plus also goes to the COM inputs of relays 2 and 3 which are switched to display either RED or GREEN LEDs. The GREEN connects to the normally closed (NC) outputs and the red to the normally open (NO) outputs. So the aspects will both show GREEN with no relays activated.
A northbound train hits the first insulated rail which connects 12v common (yellow) to the COM input of relay 4 (the one at the bottom). That routes through the NC output (orange) where the capacitor cleans up the signal and activates relays 1 and 3. That changes the southbound aspect to RED but leaves the other GREEN.
When the train hits the second insulated rail, the connection to COM at relay 1 (which is already activated) is routed through the NO connection to the orange trigger input. Relays 1 and 3 stay activated so the signals stay the same. When the first block is vacated, relay 1 continues to hold relay 3 at RED. And when the second block is vacated, the relays all turn off and the aspects return to both GREEN.
The same occurs in the opposite direction. Only the names have changed to protect the innocent. Nicely done, Stan!
Here's an 8-channel, 12V, high/low triggering with screw-terminal inputs. From what I can tell you can get 2 of the 4-channel versions with screw terminals for less than an 8-channel. There are only 2 extra wires to run if you use 2 boards (connecting 12V DC+ and DC-).
Direct links to eBay will get deleted by the moderator so enter the auction # into eBay search box: 191100390737
You can get it cheaper if you want to mess with those connector pins I mentioned above.
The auction # for the capacitors I showed earlier: 221849286345
Thanks Guys! You rock!
Just ordered, now its just a waiting game!
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