Hi,
I am new to the forum, could any one please help me.

I am trying to design a very simple Track Signaling module, which has the following functionality

1) Uses IR Sensors for the detection
2) As i need to make a few of these i would like the component list to be as small as possible
3) Below is the logic


I would like the module to detect a train passing over a IR sensor, and set a LED to Red, then to wait 2 Seconds and then reset the LED to Green, and then wait for the next train.

I dont know if this is possible but any help would be realy appreciated.

Thank you in advance
Allison

 

Hi Allison,

Welcome to AAC.

I would use any one of the many IR TX/RX pairs for detecting proximity. Use a pulsed signal to avoid interference from ambient IR. Vishay and others make them. Generally, the frequency you chose for the pulse is not important, but it is better to match the TX and RX frequencies approximately.

 

Can you do simple microcontroller programming?

 

Yes.... i was considering using the Arduino Uno.... but there will be a lot of signals so if i could achieve it by using discreet components it would be better

 

Sounds like a good to learn about the heart of the UNO. Maybe a Nano or ATTiny standalone chip.

 

Are we talking about model trains or real life-sized railways?

 

Are we talking about model trains or real life-sized railways?

I am building a Model Railway Layout

 

but there will be a lot of signals so if i could achieve it by using discreet components it would be better

A lot of signals would require a lot of discrete components. I don't see why that would be better? How many is 'a lot'?
If 3 pins of a Nano could handle one IR sensor and one red/green switch, then with 12 digital pins and 6 analogue pins a Nano could cope with 6 signals.

 

Depends on how much is a lot and how far apart the sensors are located.
One solution is to run wires back to a single microcontroller at do all the control from one central controller.
8-pin MCUs are so tiny and low priced that you can create multiple autonomous controllers very easily.

 

Depends on how much is a lot and how far apart the sensors are located.
One solution is to run wires back to a single microcontroller at do all the control from one central controller.
8-pin MCUs are so tiny and low priced that you can create multiple autonomous controllers very easily.

I wouldnt know where to start with a microcontroller, I have looked at using a Arduino

Here is the layout the > < or >< indicate directions of travel

 

Nice.
Can you tell us the scale (dimensions) so that we have an idea of the size of the layout?
How many signals in total?
Are the signals independent?
How are the signals powered? What voltage?

You don't have to use MCU. A simple 555-timer circuit might be able to do the trick.

 

How many detectors do you need?
Do you need just to detect passage of a train or its direction too?

As for approaches, it seems you will need a lot of wires (at least one per sensor) or some sort of coding and a network. I am thinking of something like how a TV remote works (https://electronics.howstuffworks.com/remote-control2.htm ). The remote sends a coded signal and the detector decodes it and does what it is supposed to do. Of course, you will need a lot of detectors too.

Each detector could send a "train pass" code to the central MCU. I did a brief search for "programmable IR detectors." That is, one that can send a unique code the central control. I didn't find exactly what I was looking for in a brief search.

As an alternative, there are some very small microcontrollers (like Microchip's 10F322 series) that could be glued to an ordinary IR detector to make it "smart." It would hardly be noticed size wise.

As mentioned, it can be done with a lot of wires to a central control panel, but that would be a lot of work and wiring. If you only need, say 10, that is not such a big deal. But 30 would be a different story.

 

Nice.
Can you tell us the scale (dimensions) so that we have an idea of the size of the layout?
How many signals in total?
Are the signals independent?
How are the signals powered? What voltage?

You don't have to use MCU. A simple 555-timer circuit might be able to do the trick.

The is approx 4.8m(L) x 3.8m(W)
At present i am looking at simple independent siganls, but later i may want to link in to 'blocks'
The signals could be powered by either 12vDC or 5vDC (resistors in the actual signal LEDs)
There could be around 50 actual Signals with around 25 IR Sensors, although these arnt finalised as yet.

It is my husbands layout, i am just doing the 'Techie' bits as he isnt good with those.

 

Are the trains powered with simple DC or are they 'digital' (DCC)?
If using simple DC you could possibly send coded signals via the rails thus eliminating the wires.

 

How many detectors do you need?
Do you need just to detect passage of a train or its direction too?

As for approaches, it seems you will need a lot of wires (at least one per sensor) or some sort of coding and a network. I am thinking of something like how a TV remote works (https://electronics.howstuffworks.com/remote-control2.htm ). The remote sends a coded signal and the detector decodes it and does what it is supposed to do. Of course, you will need a lot of detectors too.

Each detector could send a "train pass" code to the central MCU. I did a brief search for "programmable IR detectors." That is, one that can send a unique code the central control. I didn't find exactly what I was looking for in a brief search.

As an alternative, there are some very small microcontrollers (like Microchip's 10F322 series) that could be glued to an ordinary IR detector to make it "smart." It would hardly be noticed size wise.

As mentioned, it can be done with a lot of wires to a central control panel, but that would be a lot of work and wiring. If you only need, say 10, that is not such a big deal. But 30 would be a different story.

Initially it will be just an idication that a train has passed a signal, but having directional indication would be great. Most of the layout is Uni-Directional, although there are some sections that are Bi-Directional.
There could be around 25 detectors but this number could change depening on the final solution used

 

Are the trains powered with simple DC or are they 'digital' (DCC)?
If using simple DC you could possibly send coded signals via the rails thus eliminating the wires.

The Signals will be ALL DC, only the track is controlled by DCC

 

At present i am looking at simple independent signals, but later i may want to link in to 'blocks'

You could start off with simple independent signals.
However, if you have bigger plans in future it would be a good idea to plan ahead.
Can you explain what you mean by 'blocks'?

 

You could start off with simple independent signals.
However, if you have bigger plans in future it would be a good idea to plan ahead.
Can you explain what you mean by 'blocks'?

A block is a section of track that is controlled by an entry and exit sensor.... when a train enters a block, the signal is set such that a following train should not enter that block until the 1st train has left the block.

 

I have to admit that I know nothing about model railways.
However, if at some point in the future you plan on having full computerized control then now is the time to plan for this.

 

Some useful reading here:

https://www.building-your-model-railroad.com/railroad-signals.html

http://www.azatrax.com/detector-installation.html