topsy11 Posted January 7, 2015 Share Posted January 7, 2015 Hello. I've read through the topics on the hidden fiddle yards that have recently popped up and have decided I'd like to go down the route of adding a reed switch to each line which will show me which line is occupied and which is free as my fiddle yard will be hidden from view. 1.Are reed switches like L.E.D's in that they need wiring up a specific way? 2. Do they need resistors at all? 3. Can they be run off 12v DC? I'm going to have 6 lines which when occupied will change an L.E.D to red and when empty will show it as green. I'll probably keep the detection system separate from the point motor switching and indication although I'll wire the L.E.D's in to the same control panel. Thanks for any help. Mark Link to post Share on other sites More sharing options...
Theakerr Posted January 7, 2015 Share Posted January 7, 2015 No, no and Yes. Link to post Share on other sites More sharing options...
cpman46 Posted January 7, 2015 Share Posted January 7, 2015 a Reed Switch is a magnetically operated normally open (sometimes normally closed) single pole device. I assume you are going to operate it with a magnet attached to your locomotive for example. Your problem will be that the switch will only stay made whilst the magnet is in close proximity to it. As soon as the magnet moves away from the reed switch it will revert to its unenergised state. You would need to ensure that the train magnet stayed over the switch i.e. you will need to stop your train fairly precisely. This would also have a bearing on where you placed the reed switch in each road of the fiddle yard. A better system might be to have 2 reed switches triggering a bi-stable circuit to control the LED. One would be at the beginning of each road and the other just before the end of each road. A train passing over the first switch would trigger the bi-stable and light the LED. When the train leaves the road and passes over the second switch triggers the bi-stable back to its original state and switches off the LED. Although the reed switch does not need a resistor any LEDs driven by it will certainly need a resistor to limit the current through the LED. 1kOhm 0.25W is a good starting point depending on how bright you want the LED to be. Lower values will increase the brightness but I would not go much below 470 ohms running from a 12V supply. Personally I would use a single LED of a different colour to any route indicating LEDs you have on your panel. LED lit indicates track occupied, unlit track clear. Hopes this helps. Link to post Share on other sites More sharing options...
RMweb Premium Ray H Posted January 7, 2015 RMweb Premium Share Posted January 7, 2015 Mark In simplistic terms you'd connect the power supply to one side of the reed switch, the LED and its series resistor to the other and thence to the other terminal of the power supply, observing the correct polarity for the LED. A quick check of a certain Internet auction site suggests that a simple on-off version micro switch could be as much as 90% cheaper than the changeover version that you would need if you want to switch from one colour LED to another without throwing in a number of other components. You also need to remember that the reed switch will only operate when there's a magnet in close proximity. This means that you may not be able to detect whether a siding is completely clear unless you have magnets on every item of stock and probably more than one reed switch in a siding. Edited to add that Mike beat me to it. Link to post Share on other sites More sharing options...
DCB Posted January 8, 2015 Share Posted January 8, 2015 The concept is flawed. I had the same plan for operating my loft layout, The reed switch only closes momentarily as a magnet passes over it. To make a LED stay on or two LEDs change over you need a system of latching relays so the LED lights as the train passes over the first energise to make reed switch and goes off a it passes the second energise to break ( change over ) reed switch which causes the the relay to drop out and the LED to go out or the two LEDs change over.l A related problem is what how do you trigger the reed switch with? I was using magnets under brake vans to show when trains were clear of the points and in a loop with a second magnet at the far end of the loop to cancel the indications. The problem with this is some ring field magnets in power bogies also trigger reed switches. You probably need push buttons in parallel with the reed switches to set the indications when you switch the system on for an operating session. You are probably better off with Infra re, the Irdot system or similar. My planned system was also intended to change which controller controlled which section, as the train moved around the layout, I had the whole thing schemed out but the complexity and cost was horrendous. Link to post Share on other sites More sharing options...
RMweb Premium ColinK Posted January 8, 2015 RMweb Premium Share Posted January 8, 2015 Hi, I agree with last last point made by DavidCBroad, and suggest you look at the ITDOT system by Heathcote Electronics. I used it successfully on a hidden siding. I suspect it might cost a bit more than the reed switch solution, but you don't need to put magnets on your stock and it is electrically separate from track power. I've no connection with Heathcote, other than a happy customer. Link to post Share on other sites More sharing options...
Crosland Posted January 8, 2015 Share Posted January 8, 2015 You can get latching reed switches that will stay closed once operated but then you need another magnet of the opposite polarity to open it again. You can make your own latching reed switch by biassing it with a fixed magnet that is strong enough to hold once operated but too weak to operate without the additional magnet on a loco. Whether you would want to bother is another question... Andrew Link to post Share on other sites More sharing options...
topsy11 Posted January 8, 2015 Author Share Posted January 8, 2015 Thanks guys, I'll probably go for a couple of those IR detectors they seem a better alternative that reed switches and messing about with magnets!! Cheers Mark Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.