Auto Reverse using Latching Relay

[wahiba]

Hi All

Has anyone else used a latching relay as a means of auto reversing on an end to end system? I maded this test rig in the garage using Meccano, and it works!!

http://youtu.be/h9y6AUVHI8o

Circuit is pretty straight forward:



David

 

[Madman]

Wow! An Oscar is awaiting you, for short subjects, at the next Academy Award presentation.

 

[Deleted member 1986]

David, excellent idea, and the following is meant as an observation.

I notice in the above circuit the omission of reverse biased diodes, or a flywheel diodes or fly-back diodes across the relay coil.

In the absence of such a diodes, the collapsing magnetic field in the relay can generate a very high EMF which may damage devices in the input circuit, or cause arcing across the relay switch contacts.

With the diodes in place, the energy from the collapsing magnetic field in the relay coil causes a decaying current to flow harmlessly through the diodes, which will result in a slight delaying effect in operation.

John

 

[Dtsteam]

I like that... nice to see something out of the ordinary. In the days before timer reversing circuits me and a mate used the Fleischmann latching relays for a track powered system, but I like the on-board solution.

 

[nicebutdim]

I like that too. Not to be a stick in the mud but don't forget in the larger scales the sudden change of direction will quickly strip gears in any locomotive.

 

[PhilP]

I like that too. Not to be a stick in the mud but don't forget in the larger scales the sudden change of direction will quickly strip gears in any locomotive.

I would change things a little.. but it would become more complicated! :

Make the switches reeds, operated by track magnets before the end of the track..
Add a non-polarised (largish) capacitor, and current limiting resistor to store a bit of power..
Make a delay, so power goes 'off' for a short time. - Capacitor discharge lets loco slow, rather than direct stop..
Then reverse, capacitor charges for end of next run..

Mind you, I have just re-invented the 'shuttle'!!

 

[wahiba]

Hi All

thanks for the positive replys. I agree that a delay is needed. I am thinking of a timing circuit using a 555 chip. I am no expert so will be a bit of trial and error.

Reed switches and magnets are being looked at. I have the reed switches and recently got some magnets via a purchase of some SUGRU. SUGRU is used like blue tack, but over night it sets to a hard rubber. Really works. Great for fixing leads into sockets, and fittings onto model trains. It is pretty new but I have seen it in B&Q and in Hiking shops (fixes boots as well) Search SUGRU, quite an interesting product. After SUGRU plug for no kick backs have yet to try out magnets and reed switches.

I must admit I expected electrical and mechanical problems to quickly show with the quick reversing. so far none have although I have not tried it for a while.

As for the oscar. Been at home movies for over 50 years now and nothing :'(

David