# Automatic Reverse System



## THE TYCO MAN (Aug 23, 2011)

I'm one day building a layout with a straight track for a trolley line. I want it to go so far, stop, and reverse. Gets to the other end, stop, and go forward. Using DC power and the track is isolated and has it's own power.


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## T-Man (May 16, 2008)

It's been done. Here is assembly form from parts. You can buy a board that does the same thing.

I place a diode at each end. THe relay is most expensive piece. Then I used a simple timer to activate the relay.


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## DonR (Oct 18, 2012)

T-man that's an excellent system.

It can be done easier, tho not with the smoothness
of what you have.

You simply need a latching relay and two short isolated
sections at each end of the track run. The wheels of
the trolley would short between the rails at the end when
it arrives. That trips the relay which reverses polarity on
the track and the trolley goes the other way causing the
same operation at the other end. Microswitches, tripped
by the trolley could be used in place of the 2 end isolated sections.

There have been several threads on this topic. Use the SEARCH
feature in the bar across the top of the page. Enter: Reverse Trolley
and request SHOW POSTS.


Don


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## trains galore (Jul 22, 2013)

Good idea, I want to try that out
Only problem is not all my cars have metal wheels so maybe I'll go with micro switches instead. I was thinking of using a timer but given it wouldn't actually detect the train if it gets out of calibration that would be a VERY big problem!
I found some info on making a relay latch, you switch the coil with the contacts I think did it once a long time ago
Thanks!


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## DonR (Oct 18, 2012)

Yes, the isolated end sections were designed for a Trolley
and the wheels did make the connection. A micro switch
would be a better solution for both powered and non
powered cars.

I am researching the availability of latching relays. There
are a number available from various sources. 

Don


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## trains galore (Jul 22, 2013)

Hi DonR
Over here I buy my relays from altronics, I haven't ever seen a latching one but from what I worked out you simply use one set of contacts to switch the coil, found this diagram it would be perfect







Also great site here on it http://www.reuk.co.uk/Latching-Relay-Circuit.htm





Also you might have luck with RS electronics, they are expensive but you can get those unusual components


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## DonR (Oct 18, 2012)

Yes

What you depict is a one coil latching relay.

I've used those in a complex multi relay automation system
that included ability to count up to 10.

However, I have used in the past a 2 coil latching
relay. Solenoid 1 pulls the contacts left and latches
mechanically, so that loss of power does not
affect it.

Solenoid 2 pulls the contact right and latches.

There is another design. The E unit in Lionel and Marx electric
trains. A solenoid causes a drum with contacts to rotate
Wipers make contacts, thus reversing the direction of the loco.

There are also 'solid state' latching relays but I haven't had
an opportunity to use one of them.

Don


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## trains galore (Jul 22, 2013)

Ok interesting:stroke:
A relay setup that could count to ten the very early computers used relays instead of microchips, they could add numbers but filled a whole room how many relays did you need for that?
I also had no idea 2 coil relays existednever seen one.
I've started making an auto reverse with a timer kit and some other bits, putting the progress up here http://www.modeltrainforum.com/showthread.php?t=21454&page=4
Thanks!


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## rkenney (Aug 10, 2013)

Here's a 12v latching relay. First one way toggle, then the other. Note the separate momentary contacts on the upper right. From a Mercedes High beam circuit. Don't remember what year.


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## DonR (Oct 18, 2012)

Hard to see the details, camera a bit too close to the
relay.

I had not checked into them, but I have seen
several references to automotive latching relays.

Since their coils would be 12 vdc they could easily
work off power available on most layouts.

The automotive parts stores should have these at a
decent price.

Don


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## rkenney (Aug 10, 2013)

Sorry about the focus. Phones don't take good close-ups.

I fixed cars for a good many years, and this is the only latching relay I ever saw. Rather an older part so it might only be available through Mercedes, and you would be hard pressed to find an auto parts guy who could find a part based on function. All they know is application.

You might be better off going to the HVAC supplier. They have low voltage contactors that fit multiple applications and the guys seem to know how they function. Also cheaper.

Good luck.


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## trains galore (Jul 22, 2013)

Yeah the contactor is the bit in an outdoor split it's pretty much a relay that switches when the indoor unit is turned on so that the compressor/ fan start up.
I don't know what voltage they operate, but they sure can switch big currents
Might be able to get one from a recycling place or off the net, I know the installers are often the only people who can get the parts from the company itselfhwell:


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## rkenney (Aug 10, 2013)

Don't know how it is down under, but up here we have local parts suppliers and anybody can walk off the street and buy ac parts, auto parts, electrical etc. 

Years ago they used to make a big deal about only selling to people in the trade, but what they actually wanted was a tax id so they didn't have to collect and pay the retail sales tax. 

I guess that all changed to stay competitive with the internet.

AC contactors are typically 24 vac. A common door bell transformer. But they have other relays just have to poke around a bit.


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## trains galore (Jul 22, 2013)

You can buy most electrical stuff you want (plugs, sockets etc) but some specialised high voltage stuff is hard to find as the installers have an account with the companies so they they can get particular parts, generally the public can't. Trying to stop people from doing DIY stuff and don't know what they are doing. However you could probably get one second hand or on ebay 
Plus I bet you could find just about any relay here, expensive but they have some specialised parts and I think you could order online http://australia.rs-online.com/web/c/?sra=oss&r=t&searchTerm=double+coil+relay

Anyone know what this thing is?







some kind of solenoid


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## Zero Cool (Dec 4, 2013)

I work for a company that sells electrical supplies, and my guess that it's either a solenoid or a really old contactor of some sort.


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## trains galore (Jul 22, 2013)

Thanks!
My guess is it's a very old contactor as there is no mechanical linkage to the solenoid, but there are screw terminals and the little piece of wire at the end snaps back to keep the rod in a position when no force is applied.
The company is Cema- can't find anything much, apparently they do water automation, so I think it is a contactor/relay of some sort


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