Automatic stop at buffer

[ceesquared]

This is for a non dcc layout. I want to have a system for stopping a train/carrages at a buffer. I have tried using a micro switch to cut off power but that can result in a derailment. I have thought of using an IR beam interrupt to cut the power, setting up the tx is not a problem, it is the rx that I begin to run out of ideas on what I need for the circuit board. Has anybody else solved this problem? If so how, what components do you need exactly? Exit from the buffer is not a problem as it can be solved with a diode.

[peach james]

You are going to have issues with non DCC'd stock, if you run more than 1 train into the siding.  They would have to match exactly in order to get this idea to work without computer assistance...

Otherwise, I would use 3 sensors, being driven by a PIC of some sort, which pick up start speed, then apply decelleration, and the last sensor being immediately prior to the buffer stop.  The idea being that the first 2 give a speed on approach, so you can then ramp down the Voltage applied to a fairly low level, to "coast" the train to the last sensor, which then would kill the power.  Should be workable on DC, I'm not sketching it out for you. (mostly because I'm not that kind of genius, so I'd get it wrong...and try again...)

 

I would use ambient light driving CdS cells, that is what I did with bang/bang  (on/off) control on an automated layout 10+ years ago.  (using Lego RCX's as the PIC's).  Programming ran to about 10 pages of NQC, mostly to do with the 3 different bricks talking to each other.  (only 3 inputs/3 outputs on a RCX 1.0)

 

James

[melmerby]

ToF sensors (time of flight)

Use with an Arduino and mount at buffer stop facing down the track

You can set the Arduino to trigger at a given distance from the buffer

Use that to turn off power (e.g. relay) or more sophisticated to decelerate to a stop.

 

https://www.adafruit.com/product/3316

 

Edited March 3, 2020 by melmerby

[Broadway Clive]

Very simple. An Irdot from Heathcote Electronics wired to a relay that isolates the siding. (An Irdot-P can operate a solenoid to switch points)  Alternatively locomotives and multiple units can be fitted with magnets to work reed switches in place of the Irdot. I have several remote and 'hard to see' fiddle yard sidings that simply have a cut rail wired with a diode to halt the shunting locos I keep there to remove stock from arriving trains. Obviously if you are wanting to halt completely uncontrolled trains running at express speeds then you'll need to drop the speed before then - cut rails with resistors being the roughest and cheapest way, but Heathcote and others can supply modules to decelerate.

[Ouroborus]

You could do it with a photo sensor and an arduino as well.   As the wagon/carriage/loco passes over the sensor, the drop in measured light triggers an action as Keith mentions above.

[melmerby]

I mentioned ToF (Time of Flight) laser devices as I am using them to stop locos at at buffer on a DCC layout.

Although not yet installed I have tested them under working condition.

 

The VL530X module can be used for distances up to about 2m and the VL6180x up to about 200mm

You can set the trigger distance value in the Arduino sketch.

They are not affected by ambient light and will reflect off practically any surface.

They are connected by I2C to the Arduino, if you want up to 8 on one Arduino you can multiplex them with a 9548A 8 way mutiplexer. I have done that.

 

EDIT

Note these devices are really cheap.

An Arduino Nano clone & a VL6180x cost less than £5 inc post if bought from Ali Express

Edited March 9, 2020 by melmerby

[Nigelcliffe]

Also, in the Arduino theme, the acoustic range sensors in a typical Arduino starter kits are accurate enough for buffer stopping duties.   They're going to be similarly cheap. 

 

- Nigel

 

[Gordon H]

16 hours ago, Nigelcliffe said:

Also, in the Arduino theme, the acoustic range sensors in a typical Arduino starter kits are accurate enough for buffer stopping duties.  

 

If you would like to see an acoustic sensor Arduino shuttle in operation, I should have a demo on the MERG stand at Ally Pally.

It uses two HC-SRO4 ultrasonic sensors with an Arduino Uno.

[Theakerr]

7 hours ago, Gordon H said:

If you would like to see an acoustic sensor Arduino shuttle in operation, I should have a demo on the MERG stand at Ally Pally.

It uses two HC-SRO4 ultrasonic sensors with an Arduino Uno.

Are you bringing the train to an abrupt stop or a gentle slow down?

[Gordon H]

Gentle slow down, speed determined by the 'inverse' of the distance measured when within a specified range.

The track control is implemented using a second Arduino acting as a DCC command station running 'DCC++'.

[melmerby]

OP states non-DCCsystem

[Sol]

In the books by Roger Amos  Practical Electronics for Railway Modellers

Project 3 in the first Volume  &  Chapter 22 in Volume 2 have a lot for this auto stop at buffers.

 

As I don't want to get caught up in Copyright rules, I won't post the drawings but you maybe able to obtain the books from your local library or if in a model rail club, a member may have them.

[Gordon H]

20 hours ago, melmerby said:

OP states non-DCCsystem

So what?

I didn't claim my demo implementation would be directly suitable for the OP - just that you can see something akin to it at the AP show.

Nothing to stop the same principle being used with a DC system.

Indeed, the same hardware could be adapted to generate a PWM track signal instead of DCC, just needs different code.

[Theakerr]

9 hours ago, Gordon H said:

So what?

I didn't claim my demo implementation would be directly suitable for the OP - just that you can see something akin to it at the AP show.

Nothing to stop the same principle being used with a DC system.

Indeed, the same hardware could be adapted to generate a PWM track signal instead of DCC, just needs different code.

Now I would be most interested to see how you would generate a PWM signal that slows the loco down without causing it to have a complete whine out.  Easy to say.  I have put this question to MERG in another way before but basically I got nothing back.  I have tried it myself using a L298 with no sucess.

[melmerby]

2 hours ago, Theakerr said:

Now I would be most interested to see how you would generate a PWM signal that slows the loco down without causing it to have a complete whine out.  Easy to say.  I have put this question to MERG in another way before but basically I got nothing back.  I have tried it myself using a L298 with no sucess.

https://www.arduino.cc/en/tutorial/PWM

Make the frequency high enough and it should work. (it's about 500-700 Hz with Arduinos)

 

 

Edited March 13, 2020 by melmerby

[Theakerr]

18 hours ago, melmerby said:

https://www.arduino.cc/en/tutorial/PWM

Make the frequency high enough and it should work. (it's about 500-700 Hz with Arduinos)

 

 

Thks.  I had found this page but it relates only to a descriptor not a how to and it doesn't cover anything above 5V.