Model Train Switch Control with an Arduino! 

Jimmy, you can do that with just one relay. the open close of a relay can change which side of the relay is being sent. So you can have up to 4 switches on one shield. Josh

As a professional C and C++ programmer, I'd like to share some feedback on your sketch. First, remember that you are writing code for the person who's going to maintain it down the line. Even if that person is you! I can't tell you the number of times I've gone into code that I wrote only six months prior, and could not immediately see what was going on. To aid in that department, I'd like to offer some tips I've learned: - avoid using enums that differ only by a numeric suffix. I should be able to look at your enum list and understand immediately what each value is for. ST_OFF1 and ST_OFF2 do not immediately tell me what they are for. - Comments should document the "why", not the "what". I can see the "what" by reading the code: switchState = ST_TURN; does not need a comment. - Avoid "magic numbers". you nicely provided aliases Red, Green, and button for some I/O pins, but you left 6 and 7 as "magic numbers". On the code itself, I can see some room for improvement. You're tracking four states, when you really only need to track 3: set turnout to Mainline, set turnout to Diverge, wait for person to let go of button. Also, in the setup() function, ensure that the turnout matches the state. As it is right now, your code assumes that when it powers up, the turnout is in the mainline (straight) position - if you power up with the turnout in the diverge position, then you'll have to push the button twice to get it into the correct position. I'm not (yet) familiar with Arduino programming, but you should not need to write the same value to the same output twice. In switchturn you call digitalWrite(7, LOW) twice. Unless there's some quirk of the Arduino that I'm not aware of, only one is necessary. My version would look something like this (warning: uncompiled and untested code, for illustration purposes only): int mainlineRelay = 6; int divergeRelay = 7; int button = A0; bool isMainline; void setMainline() { digitalWrite(mainlineRelay, HIGH); digitalWrite(divergeRelay, LOW); delay(200); digitalWrite(mainlineRelay, LOW); isMainline=true; } void setDiverge() { // left as an exercise to the reader :) } void setup() { // as per your original code, plus: setMainline(); } void loop () { if ( analogRead(button) > 500 ) { if ( isMainline ) setDiverge(); else setMainline(); // Wait for operator to release the button while ( analogRead(button) > 500 ) delay(100); } } One thing I'm not sure of, is if the Arduino likes embedded loops like the one I have waiting for the operator. If not, then you can change loop() to: bool isWaitingForButtonRelease=false; void loop() { if ( analogRead(button) > 500 ) { if ( ! isWaitingForButtonRelease ) { if ( isMainline ) setDiverge(); else setMainline(); isWaitingForButtonRelease = true; } } else { isWaitingForButtonRelease = false; } } I hope you find this helpful. By the way, while I was analyzing the code I paused the video, and I kept trying to scroll up and down through the code. As you can guess, that didn't work :D Thanks for all the videos! Now, what was I looking for when I came across this video?

You can improve things with a latching push button. Adding an led to the button bias resistor gives an indicator. The required state is remembered through a power off sequence. And the code is simplified.

i do follow the wiring but maybe some people like to see a schematic. Especialy when in future there is more to wire like signalling or when sensors are added. Nothing fancy , the old pen&paper will do fine. Nice vid keep them comming thanks

Apologies in advance for a couple of dumb question from a total newbie...but here goes! My Bachmann turnout comes with a button and a wire to run it from a power supply. When connected, it does exactly what's depicted in this video but without the Arduino. What is this Arduino setup doing differently than my non-Arduino setup? Do some turnouts (such as the one in this video) not include a switch and power hookups? If that's the case, it seems like overkill to use a computer to handle this kind of task. Again, sorry for the dumb questions and thanks for the video.

Looking to try to implement this instead of my Atlas switch machine MOM-off-MOM buttons. I want to include some LED's into the mix to indicate point direction too... Thanks for this tutorial.

Very interesting. Can you only throw one turnout? Do you need additional relay boards to control more than one turnout? Edit: Just saw your reply to AJ. You answered my question.

Very cool, thanks for the information, these are great tutorials

I've thought about that idea, but I would rather do it automatically like install an IR sensor for when a train (or trains) are coming near and the arduino throws the switch or switches. That way the trains can proceed to the next model country.

Great presentation Jimmy ,i use a Mega so i get more I/O pins ,keep em coming buddy ,Much appreciated ,Take care till next time ...Mac

Good morning Jimmy, I enjoyed that video. I'm one for running as much "stuff" on any given Arduino as I can. I used your Track Signaling video to do my own thing and have gotten two sets of signal lights to run in the same sketch on a Nano. One is a two light tower set and the other is a three light tower set. So what I'm getting at here is to control as many turnouts as possible with as little electronics as possible. NESR says he using a Mega, would that allow for more relay connections for more turnouts? Can the relay cards be stacked? Hmmmmm, lots of food for thought. Thanks.

Thanks for all the good info. A question - at about 1:00, you say "12V power supply with adapter". Is it 12V AC or DC ? What's the current rating ?

Nice your explanation about set up Arduino !!!! Thank you :-)

Hi, I have mastered the project so far , but you mention controlling indication LEDs at the beginning of your sketch, then there is no further information. Has there been any progress on this you can share ? Regards Robert

I'm planning to use this for my turnouts, but how many turnouts can I hook up to 1 relay shield. I was thinking 2 to 4 turnouts per shield ? Or do i have to buy 1 relay per turnout. As you can tell I'm a beginner at this.

Two questions: 1. beginning at 3:10, since there are three connections per relay, why can we not just use the third connection of "Relay 2" to switch the track from the turn to the straight? If you have a link that can explain the 4 Channel Relay Shield, I am okay with that. 2. at 15:05, I understand that the analog input can be a number between 0 and 1024, but how does the program sense that from the button?

Hi, first of all, thanks for sharing. You, amongst many others, are very much into Arduino products. This, though, seems like a lot of effort. Maybe you can explain to us ignorant MRR folk, i.e. old guys, why go to all this effort. What is the underlying reason? Thanks in advance for your reply/comment.

I find this very hard to follow without a schematic diagram

Is there another relay board we can use as the one you list won't ship to Canada

I just have an 8 channel relay board can I use that instead of a relay shield?

Hi Jimmy. Another enjoyable video. Since any microcontroller, like he ATMega 328 on the Uno, has a limitied amount of program space (and memory space) I optimized your code to get the size down as low as possible (both program space and memory space). I have not tried this yet as I am still at work (don't tell the boss I was watching a DIY & Digital RU-vid video while still on the clock!). The sketch compiles without errors (checked at www.arduino.cc using the web based IDE) and I will let you know if it actually works when I get home and can give it a go on my Uno. Thanks again for all the great videos you post. Rick #define Red 12 //these first 2 will not affect the program but will let you hook up signal lights #define Green 13 //Hook up the lights to pins 12 and 13 #define button A0 #define Relay1 6 #define Relay2 7 void setup(){ pinMode(Relay1, OUTPUT); //establishing Pin 6 as output, controls a relay pinMode(Relay2, OUTPUT); //establishing Pin 7 as output, controls a relay pinMode(button, INPUT); //establishes button as input pinMode(Green, OUTPUT); //establishes pin 13 as output pinMode(Red, OUTPUT); //establishes pin 12 as output digitalWrite(Relay1, LOW); // make sure Realy1 is off digitalWrite(Relay2, LOW); // make sure Realy2 is off } enum SWITCHSTATES { ST_OFF1, ST_OFF2, ST_STRAIGHT, ST_TURN, }; SWITCHSTATES switchState=ST_OFF1; // Set initial state to ST_OFF1 void loop(){ int buttonRead=analogRead(button); delay(200); if (buttonRead > 500) { // if button pressed then switch(switchState) // process the button press { case ST_OFF1: // if current state is ST_OFF1 then set the swtich to straight switchstraight(); //sets up changes to ST_STRAIGHT break; case ST_OFF2: // if current state is ST_OFF2 then set the switch to turn switchturn(); // sets up changes to ST_TURN break; } } } void switchturn(){ digitalWrite(6, HIGH); //activates relay 1 delay(200); digitalWrite(6,LOW); //turns off relay 1 switchState=ST_OFF2; //chages to ST_OFF2 } void switchstraight(){ digitalWrite(7, HIGH); // activates relay 2 delay(200); digitalWrite(7,LOW); //turns off relay 2 switchState=ST_OFF1; //chages to ST_OFF1 }

Hi anyone can answer me, if it possble to add Position LED on this project... thanks!

hi, just uploaded your sketch , to arduino and relay board nothing else connected am getting this error message . Any ideas? - regards Robert Arduino: 1.8.13 (Mac OS X), Board: "Arduino Uno" Sketch uses 1238 bytes (3%) of program storage space. Maximum is 32256 bytes. Global variables use 11 bytes (0%) of dynamic memory, leaving 2037 bytes for local variables. Maximum is 2048 bytes. Problem uploading to board. See www.arduino.cc/en/Guide/Troubleshooting#upload for suggestions. avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00 avrdude: stk500_recv(): programmer is not responding avrdude: stk500_getsync() attempt 2 of 10: not in sync: resp=0x00 This report would have more information with "Show verbose output during compilation" option enabled in File -> Preferences.

Maybe I'm missing something, why go to this effort and expense to do what a simple switch can do? I suppose it is part of a larger scheme.