Glen Ogle

[gtmspyder]

Hello again, I have been a little unwell, so have not done much to Glen Ogle recently but to continue this long winded saga, I need some help from the electronics wizards on here.

The storage short sections have a reed switch laid in the track that operates a relay to change the green LED to red when the section is occupied, these are operated by small Neodium magnets glued to the bottom of each loco.

The loco's do not stop in the same place exactly enough to position the magnet over the reed switch, so it is a 50/50 chance whether the occupancy red LED is lit or not.to

Has anyone any ideas as to how I might overcome this problem.

I have tried putting more magnets under the locos, but this is still hit and miss, and there is a limited amount of room under there anyway due to clearances crossing the point switch rails.

I did wonder about a capacitor in each relay switching wire as some sort of hold on delay.

Your collective thoughts would be appreciated.

As always, many thanks to any responders.

Regards,

BrianT

[Frank]

Hi Brian,

Sorry to hear you've not been well.   Hope you are on the mend now.

If you put some sort of delay in the relay circuit ( it would probably be a bit more complicated than a capacitor but not necessarily much more complicated) then it would still only hold the red LED on for a limited period of time.

It is possible to have a system where you have two reed switches, so the LED is switched when the loco enters the section and switched back when it leaves.  This would be more complicated of course.

Do the locos drive into the sections and then out the other end or do they drive in and reverse out?

Frank

[gtmspyder]

Hello Frank, the loco's pass through the dead sections, and are held there until required, then they continue in the same direction.

A delay, whilst not absolute, would be better than the quick on/off flash that I usually get at the moment, at least it would have time to register.

Obviously, a permanent on until the loco moves would be much better, but I realise that this would require a lot more circuitry, and probably some additional circuitry from the track position, which I don't particularly want to do as I have already used all 25 wires at my disposal from the control panel to the track boards.

Regards,

BrianT.

[gallopingalice]

Whilst simple latching circuits are easily conjured in electronics, the devil lies in the detail.
To be of help, we'd need a diagram to show how things are wired now, and where the bits are relative to the connector. We'd also need to know, in detail, how the parked train is re-awakened; for example;

[gtmspyder]

Hello Richard, thank you for your kind offer.

I have just sketched out a simple drawing showing the circuitry for the storage sidings off scene.

It is simply a facility to hold two clockwise and two anticlockwise  running trains, on a parallel track configuration behind the scenes at the bottom left of the layout behind the loop of Lochearnhead station.

This is achieved by the simple expedient of cutting one of the rails twice, a little over a loco length apart, where I want the train to stop, thus isolating this short section of track from the section feed, and bringing the loco to a halt.

This situation is reversed by operating a normally open push button switch to feed power to the short section of track, long enough for the loco to pass over the track break and get onto track fed by the section feed proper and continue on it's way.



In the middle of this short section of isolated track, is positioned a reed switch, which is operated by a magnet fixed to the underside of the loco.  This micro switch is wired into the operating coil circuit of a small single pole change over relay (SPCO) in the control panel, the changeover contacts of which select a green/red LED, to indicate track unoccupied (green) or occupied (red), as the magnet activates the reed switch.

The problem I have is that as the loco passes over the reed switch onto the dead section of track, it does not necessarily stop with the magnet over the reed switch, resulting in only a quick flash of the red LED before reverting to green, leading to uncertainty as to the loco's position, because of course, should the loco overrun the rail break, it will come back onto the live section of track and continue on it's way.

I have tried additional magnets under the loco with mixed results, because I suspect the adjacent magnets are cancelling each other out, resulting in one or two quick flashes of red as before.

I thought that an inbuilt release delay on the relays (Hence my thoughts of a capacitor being charged to hold the relay for a period of time[/i].)would at least show red for a longer period of time and satisfy my need to be certain that the loco and it's train were stopped and held in position, although ideally, a permanent red showing until the push button is operated to release the loco on it's way would be the best.

I like the idea of additional reed switches in a parallel configuration covering the length of the dead section, as this is relatively easy to do, and simpler than having a latching relay with a separate release reed fitted upstream of each section to reset the latch, but I am open to further thoughts and circuitry on the subject, as long as it does not entail further wiring between the control panel and the track, as I have no wires spare in the 25 way D plug/cable I am using to interconnect the control panel and track, especially as this has to happen in seven different places around the track configuration.

So there you are folks, that's your starter for ten as Paxman would say.

Regards,

BrianT.

[gallopingalice]

Ta for your diagram. Its just as I'd imagined.
The prototype latch module will be about the size of a large postage stamp, with three transistors, 3 resistors and a diode, on it. 4 wires are attached for connection to + voltage (red), ground/0v/- (green), relay feed + from reed (orange) and the track feed of the push button output(yellow).

Questions:
1, what is the plus voltage to the relay?  (affects resistor values)
2, what current does the relay take or what is it's coil resistance.  (affects the current rating of one of the transistors, TR1)

Once I have the answers I'll knock one up and call here for delivery details.

Richard
PS. how does one include a picture/diagram

[Hugh Norwood]

Brian, is that reed switch NO or NC?
I ask because you can make a relay latching with just two resistors...
I'll try to dig out the diagram for it...

[gtmspyder]

Hello Richard and Hugh, thank you for your help.

Hugh first 'cos I know that answer off the top of my head:-  The reed relays are normally open, and as an aside, there are seven relays for seven short holding sections throughout the length of the layout . 

Hence any additional wiring between control panel and baseboards required, would need an additional, albeit smaller D plug,  to interconnect all four sections of the baseboards together, possible but a chore.

Richard, I will get back to you in answer to your questions as soon as I have put my test meter on the various parts of my existing circuitry.

The reason I cannot give a definitive answer now, is because all this circuitry is fed from my hand-held Gaugemaster control, (shown fixed to the right hand side face of the control panel in the pictures), using the controlled 12v dc for the loco's.  The 16v ac, rectified and smoothed, is used for the point motor supply, and from this, via a variable voltage control,  (shown on the opposite side of the control panel front),  to adjust the diode voltages and hence there brightness , so I am uncertain of all three of the voltage outputs with out measuring them.

Regards,

BrianT.

[Hugh Norwood]

OK here we go


it relies on the fact that a relay can hold-in on a lower current than is required to operate it. The resistor in series with the relay coil provides enough current to hold it "on" but not enough to make it pull in, so the relay is usually "off"

A brief push of the upper push switch (or your reed switch) makes enough current flow through the relay coil to cause it to operate, after which the current flowing through the resistor keeps it "on".

A brief push of the lower push switch shorts the relay coil and the relay drops out.

You need to select the resistor to match your relay and the voltage supply. Obviously you need one resistor per relay and the get warm so you need  1W resistors

(PS I should say I have 12 relays in the control box on Angst driven by this circuit)

[gallopingalice]

Nice one Hugh! I'd forgotten that property of relays.

I was concentrating more on an entirely add-on solution to an existing set up.

Richard

[gtmspyder]

Thank you Hugh, a very elegant solution, with all the wiring required inside the control panel, and apart from getting the correct one watt resistor size to put into the relay feed from the reed switch, I have only to sort out the relay dump circuit switching, and the jobs a good-un.

Does anyone know of any miniature double pole, push to make switches??? ::) ;D while I trawl the internet myself.

Once again, this sites never ending usefulness is superb.

Kind regards, to all who have offered help and solutions,

BrianT.

[gallopingalice]

Would a double pole toggle do?

[gtmspyder]

Hello again Richard.

A double pole toggle would do and I have some, bot I would rather have the push to make type, but if I can't find any, then I may use the DPCO type I have in stock, or even buy seven Double Pole sprung off toggle types, which I know are available if all else fails.

Regards,

BrianT.

[gtmspyder]

To continue with the work on the control panel, which is now I think/hope, is complete.

I took HughN's advice, and added a latching circuit to the already fitted single pole changeover relays that change the mini storage section diodes from green to red when a loco occupies the section.

Hugh's provided circuit is very simple and elegant, needing only a reduced voltage permanent feed to the relays that require latching, which, while incapable of pulling the relay on, will hold a relay latched if it is pulled on by a greater voltage, which, momentarily the reed switches provide as the loco passes above them does.

We now have the track indicator diode turned from green to red by the SPCO relay, and latched permanently on, until the circuit to the relay is momentarily broke.

The short storage section had a momentary action push to make switched feed from the track circuit feeding it, now if this had been a double pole switch, I could have used the second unused pole to break the latched relay's circuitry, thus letting the relay drop out.

Unfortunately, I could find no supplier of miniature double pole momentary push to make switches, so I have scrapped the push switches and used instead, momentary action double pole toggle switches, which now feed the short isolating sections with power to move the loco of the short dead section of track, whilst at the same time, cancelling the latch circuit to the relay, and thus resetting the red/green track diagram indicating LED back to green until the next actuation.

All this wiring I was able to carry out within the control panel itself, thus requiring no extra wires back to the layout.

It did get rather complicated within the control panel, wiring in the resistors to each of the seven fitted relays, and getting a stable controlled voltage feeding the resistor feed circuit, changing the seven mini section switches buried in among all the diode wires plus the additional wiring required, I prevailed in the end.

I found on Ebay a voltage reducer that would drop the voltage from the 20v I had available to 12v, and it even had a readout showing the voltage adjustments as I made them, all for less than

[The Sales Team]

Well, Brian - all this complicated electronics is most impressive but I'm afraid has left me way behind...!

I'll be more engaged when you start using the tea strainer, and will be interested to hear how it does.

David (Collins)

(- for it is he - logged in with his alter ego! Apologies.)