Alternatives for point/turnout operation

[yb281]

Don't real railways use something called a 'track circuit', maybe you could use something similar. It would require the use of non insulated metal wheels.

http://en.wikipedia.org/wiki/Track_circuit

There was an article on this (or something very close) in Garden Rail 210 February 2012.

 

[bobg]

Generally I've found that ordinary micro-switches are fine outside, with a smear of silcon grease round the seams, and then kept covered, so no direct water contact.

Track circuiting would be a good way to go but for the insulated wheelsets, because the 'section' could be as long as needed to trigger the point motor. I suppose some sort of bridging for the insulated wheels would work, but that still makes life difficult for visitors, which brings us back to doctoring a wagon (or six)
.

 

[bobg]

The only small issue is finding suitable waterproof microswitches. Pulse length is not too much of a problem, use a simple 555 monostable to give a longer pulse. How about a small, very thin strip of brass fixed (from the outside) so there is a tiny gap above rail height, when the wheel passes over it pushes down on the strip and makes the circuit. You could even place a small recess in the rail top so the strip sits in it when the wheel pushes down.

I get the idea of these 555s but don't know how it works, power, postion, suspeptability to adverse conditions etc.

 

[tramcar trev]

I looked at an optical detector and would have used it except that I had a heap of reeds but the optical detector works as soon as something shades the beam.. I'll try and round up the circuit.... ahh found it:
http://www.mrollins.com/photodet.html all waterproof no moving bits to the detector...

 

[nicebutdim]

The only small issue is finding suitable waterproof microswitches. Pulse length is not too much of a problem, use a simple 555 monostable to give a longer pulse. How about a small, very thin strip of brass fixed (from the outside) so there is a tiny gap above rail height, when the wheel passes over it pushes down on the strip and makes the circuit. You could even place a small recess in the rail top so the strip sits in it when the wheel pushes down.

I get the idea of these 555s but don't know how it works, power, postion, suspeptability to adverse conditions etc.

They need a 12v supply and I place mine in the outdoor junction boxes/enclosures and attach to the nearest fence post etc. In the same enclosure you can place required relays and connections.
For convenience and price you can't beat this http://www.maplin.co.uk/555-monostable-switch-kit-220009 < Link To http://www.maplin.co.uk/5...able-switch-kit-220009 but you do need to solder up the kit.

 

[MRail]

Don't real railways use something called a 'track circuit', maybe you could use something similar. It would require the use of non insulated metal wheels.

... and clean rails/wheels of course.

 

[bobg]

The only small issue is finding suitable waterproof microswitches. Pulse length is not too much of a problem, use a simple 555 monostable to give a longer pulse. How about a small, very thin strip of brass fixed (from the outside) so there is a tiny gap above rail height, when the wheel passes over it pushes down on the strip and makes the circuit. You could even place a small recess in the rail top so the strip sits in it when the wheel pushes down.

I get the idea of these 555s but don't know how it works, power, postion, suspeptability to adverse conditions etc.

They need a 12v supply and I place mine in the outdoor junction boxes/enclosures and attach to the nearest fence post etc. In the same enclosure you can place required relays and connections.
For convenience and price you can't beat this http://www.maplin.co.uk/555-monostable-switch-kit-220009 < Link To http://www.maplin.co.uk/5...able-switch-kit-220009 but you do need to solder up the kit.

The 12v supply might be a minor problem (maybe not impossible) due to where the whole thing would be. Unfortunately Maplin's O.O.S. at present, I'm tempted to get one to play with.

 

[nygma]

Going back to the track circuit and the blade: what if you create an insulated section on one of the rail, and place a piece of copper plate on flange level. Apply voltage to the insulated section. Wheel of the passing train will short the circuit between the rail and the contact metal. Maybe you can use a piece of guard rail as contact metal placed close to the stock rail.
I am not sure if this was suggested in the earlier posts.

 

[Neil Robinson]

The 12v supply might be a minor problem (maybe not impossible) due to where the whole thing would be. Unfortunately Maplin's O.O.S. at present, I'm tempted to get one to play with.

The 555 chip itself will work from 4.5V to 16V and takes very little current so a rechargeable 9v battery would be fine just for the chip.
I assume the Maplins kit needs 12V because its relay most likely has a 12V coil.
You'd also need power to operate the point motor and for an LGB one this can approach about 1A momentarily.
I've just built a 555 timer circuit with a 12V relay, this takes about 0.01A with the relay off and 0.05A with the relay on, so I reckon any 12V battery pack that can stand 1A short term discharges would work.

 

[bobg]

Going back to the track circuit and the blade: what if you create an insulated section on one of the rail, and place a piece of copper plate on flange level. Apply voltage to the insulated section. Wheel of the passing train will short the circuit between the rail and the contact metal. Maybe you can use a piece of guard rail as contact metal placed close to the stock rail.
I am not sure if this was suggested in the earlier posts.

I think what you are suggesting is to make the wheel itself into the switch, rather than operate a microswitch. That means that wheel/rail contact must be kept good at all times. With steamers oil might be a problem.

 

[nygma]

I think what you are suggesting is to make the wheel itself into the switch, rather than operate a microswitch. That means that wheel/rail contact must be kept good at all times. With steamers oil might be a problem.

Yes, this was my suggestion. Not that I have tried before, but I would imagine that no matter how much oil you have on the wheels, it is still the rails the wheels ride on not on a film of oil. And it is only a short section of rail that has to be kept clean. Using a guard rail as contact would use the inner surface of the wheel which is usually cleaner.

 

[bobg]

I think what you are suggesting is to make the wheel itself into the switch, rather than operate a microswitch. That means that wheel/rail contact must be kept good at all times. With steamers oil might be a problem.

Yes, this was my suggestion. Not that I have tried before, but I would imagine that no matter how much oil you have on the wheels, it is still the rails the wheels ride on not on a film of oil. And it is only a short section of rail that has to be kept clean. Using a guard rail as contact would use the inner surface of the wheel which is usually cleaner.

It bears investigation, as the inner contact could be made as long as required.

 

[bobg]

Been thinking about the circuit required and realise that it needs either dual pole microswitches or relays. Just a minor complication.