# Mechanical auto reverse?



## santafealltheway (Nov 27, 2012)

Google hasn't been very helpful... I've tried searching but i cant find anything but DCC which i don't have the $$$ for.

i DO have a drawer full of switches and relays...

I had to give up my space for a layout, and I'm moving to a wall mounted run, and I'd like to know how to mechanically auto reverse... i just don't get how it works....

any input would be greatly appreciated.

I just have standard 2 rail HO track and non-dcc engines.

Thanks!

really im just trying not to spend 50 bucks to make it go back and forth, im sure i can do it with what ive got...


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## DonR (Oct 18, 2012)

Hey Santa Fe

My layout is all Santa Fe by default...my first locos had that road name
and it stuck...basically the setting is in a Southwestern valley.

But as to your auto reversing.

Not sure what you want to do. Can you explain more
precisely how your idea would play out?

Auto reversing can be done easily with relays but they will require some sort of
'sensing' the presence of the train at the points where you want to reverse.
There are a number of ways to do that. But likely from what you say
you have on hand what you'll need.

It's simple on DC. The relay reverses track polarity and train goes
back where it came from then again trips a sensor; track polarity
again reverses to send train to starting point over and over again. 

There is a thread here on the Forum where a poster wanted to do this
with a trolley. Some posts on that thread may be of help to you.

Give us more info and let's see if you can get 'er done.

Don


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## santafealltheway (Nov 27, 2012)

*details*

so i just have a straight run across my wall, about a 50 foot line.

i just want it to go back and forth, and while it would be nice to have a delay at each end, it's not really important.

I was thinking using a micro switch at each end to trip a relay? or something?

It's just bachmann ez-track and the cheap santa fe engine with some cars.

i just dont wanna shell out 50 bucks for the chip and sensors at caboose hobbies.

my main issue is that i dont really understand electricity...

so any ideas are appreciated..


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## gunrunnerjohn (Nov 10, 2010)

If you can't build simple circuits, the $50 is looking like the attractive option.


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## DonR (Oct 18, 2012)

It can be done easily.

You need a micro switch tripped by loco or end car at each end of your track.

You would need a latching relay with double pole, double throw contacts DPDT.

There are different designs for latching relays so the actual connections
would depend on how it operates.

The track is connected to the center tabs of the relay contacts.
Power pack supply is connected to the tabs at one end. 
Then wire Left tab from power pack to Right tab other end of contacrts.
Wire Right tab from power pack to Left tab at other end. This forms an X. 

Thus:

The train is reversed when it hits microswitch triggering relay. The relay operates and reverses polarity on the track. The train goes the other way until it hits microswitch
on other end and again triggers relay and train returns...and so on endlessly thru the night.

It's that simple.

You say you have a bunch of relays. Are any latching? By latching I mean when
the coil is triggered the moving part changes the contacts and MAINTAINS that contact
even after coil is de-energized.

Normal relays change contacts ONLY while coil is engergized.

Don


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## santafealltheway (Nov 27, 2012)

excellent... i just didnt know if it was possible..but i was sure there was a non computerized way of doing things. a "Latching DPDT" relay you say. alright. and i just wire the double throw up to the rails in opposite polarity?


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## DonR (Oct 18, 2012)

santafealltheway;. and i just wire the double throw up to the rails in opposite polarity?[/QUOTE said:


> Not sure what you mean...but:
> 
> The track lead is connected to the CENTER tabs on the relay. Both Power Pack
> feeds to one end...and the inverse of the power pack feeds to the other...the
> ...


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## santafealltheway (Nov 27, 2012)

Thats pretty much what i meant. any idea where i could find one around town? i dislike online shopping.

I dont know is that something an autoparts store might have?


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## DonR (Oct 18, 2012)

Maybe one of the Forum guys has a latching relay laying
idle in a parts drawer...ANYONE?

I doubt that Radio Shack would stock a latching relay but it's worth
asking. The ones I've used had 2 coils, but I've seen others that
used a ratchet type mechanical arrangement triggered by a solenoid.

If you have an electric distributor nearby they could check their stock
or perhaps order one for you. Your power pack accessory terminals
put out around 14 or 16 volts AC best I can recall. You'd need to
get a relay with coils that work at that voltage. Since the pulse is
momentary it wouldn't matter whether it's designed for DC or AC.

What relays do you have in that 'drawer"? You might have one. If
not perhaps I can describe how to make such a circuit out of
what you have...Check the number and type of contacts on
each relay...single pole
double throw, double throw double pole, or hopefully, relays with
multiple contacts. I can work with those for you.

Don't forget, you'll also need 2 momentary microswitches (normally open) one
for each end of the track.

Don


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## T-Man (May 16, 2008)

How long does it take to travel fifty feet? I use a simple timer with diodes at each end. I just figured out how to increase the time. The original was 1 minute with return time of 30 seconds. A short track would have stops in relation to the time traveled.

This shows the first two threads

Just to build one with Radio Shack prices is half the price of your LHS.


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## DonR (Oct 18, 2012)

t-MAN

Another idea always good.

Interesting system. I like the idea of the
car staying still for a short period. That
can also be accomplished by resistors that
decrease resistance over a time period (different
times are available).

It may be more complicated than
Santa Fe wants to attempt.

But several choices is a good thing.

Don


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## T-Man (May 16, 2008)

I played with speed reduction to track sections. You need high wattage resistors to be specific. I/2 watt just heat up to much. I used 1n4001 diodes next and the 1 amp rating was also hot. SO you are looking at 3 to 5 amp diodes . Each one reducing the voltage by .7 volts. You need a lot of them to have some kind of step increase. I stopped at 1 amp in my testing.


Dallee does make a unit that has a brake and slow start but it has to be a large piece of track. There is no specifics on how to set it up so a lot of testing is needed.

If you keep the speed slow you will not notice the sudden start.


The reverse circuit is a common request. It is one reason why I decided to show how to do it. There is plenty of information and options. I would like to see him do a mechanical method.

In theory a diode would stop the train. A micro switch would activate a relay to reverse the power.
The problem is the delay. How? If you go with a timer that is what my board does. I use the my loosely the ideas was drawn up by others. He could use a button too, rent a kid to push the button when the engine reaches the end.

Mechanical would be cool. there are block wiring circuits that may help. Just google toy train revue.

In a way the electrical board is simpler.


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## santafealltheway (Nov 27, 2012)

*ha!*

okay thanks guys, got it figured out, found a latcher in the pile after testing about 60 of em haha.

hooked up my teeny switches and off she goes!


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## DonR (Oct 18, 2012)

You got it working...FANTASTIC. :appl:

Can you send us a pic or Video?

Don


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## santafealltheway (Nov 27, 2012)

it'll be a while, my camera is on the fritz


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