RMweb Premium dale159 Posted June 5, 2014 RMweb Premium Share Posted June 5, 2014 Hello everyone, I have built two Scissor crossings for use on my layout using 4 modified Peco points and a small diamond crossing. However I am a little unsure as to how to wire them up for use on the layout, I would like if possible to automate the operation so that all I need to do is operate the point motor switches. The letters A-H represent the various crossings and the numbers 1-4 represent the points. A mimic of what the polarities will need to do with each route set, the blue in the top diagram represents a dead section With reference to the top picture I have made the crossing so that the triangle between points A,B&E is fed as one piece and likewise with points C,D&F I would like the crossing to be capable of the following Change the polarity of ABE when either point 1 or 2 is reversed, but not both Change the polarity of CDF when either point 3 or 4 is reversed, but not both G&H will only be energised when the points are reversed as no trains will pass over with both straight routes set Use the reversal of 1 or 3 to energise G and the reversal of 2 or 4 to energise H, hence the requirement for only one crossover to be set at once rather than both together as this would cause a short at G&H. A friend also suggested interlocking it so that reversing one crossover would prevent the other being reversed without first returning to the straight ahead route. I was intending to use Seep PM1 motors with built in switches, I could also use additional motors in parallel with those on the points if more switches are required, so long as my CDU is up to throwing that many simultaneously, or other motors if they would be more suitable. I had mentioned in my layout thread about using 2 separate DC controllers for the two loops but having the scissor might make that difficult, as well as being able to go DCC. Any assistance with that would be greatly appreciated. Many Thanks Dale Link to post Share on other sites More sharing options...
chaz Posted June 6, 2014 Share Posted June 6, 2014 You could use a 3 position rotary switch, this would make the interlocking easy - the switch would be assigned straight ahead, crossover 1/4, crossover 2/3 - so not possible to set both crossovers at the same time. Use one pole to switch the point motors. You could use the internal switches of the point motors to switch the point crossings. If you choose a muti-pole rotary the extra pole(s) could be used to switch the crossings of the diamond. I do realise there's some detail to work out to do it this way but it does offer a neat way of operating your scissors. By the way - forget your blue dead sections - they can be left on. Chaz Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted June 8, 2014 Author RMweb Premium Share Posted June 8, 2014 You could use a 3 position rotary switch, this would make the interlocking easy - the switch would be assigned straight ahead, crossover 1/4, crossover 2/3 - so not possible to set both crossovers at the same time. Use one pole to switch the point motors. You could use the internal switches of the point motors to switch the point crossings. If you choose a muti-pole rotary the extra pole(s) could be used to switch the crossings of the diamond. I do realise there's some detail to work out to do it this way but it does offer a neat way of operating your scissors. By the way - forget your blue dead sections - they can be left on. Chaz Chaz, I wouldn't be able to use the rotary switch with Seep motors as like the Peco motors they require a momentary toggle or push to make switch, for that to work I would have to use a tortoise motor or similar which I'm not sure I have enough room under the board for. Also the crossings at G & H vary in polarity depending which crossover is in use which is was provoked the though to leave them dead if both were set straight ahead. Dale Link to post Share on other sites More sharing options...
RMweb Premium Siberian Snooper Posted June 8, 2014 RMweb Premium Share Posted June 8, 2014 Chaz, I wouldn't be able to use the rotary switch with Seep motors as like the Peco motors they require a momentary toggle or push to make switch, for that to work I would have to use a tortoise motor or similar which I'm not sure I have enough room under the board for. Dale You could use the rotary switch with a momentary switch in the feed, that way you could set the route up and then push the button to make it happen, a CDU would also help. SS edit to add CDU Link to post Share on other sites More sharing options...
DCB Posted June 8, 2014 Share Posted June 8, 2014 You could use the rotary switch with a momentary switch in the feed, that way you could set the route up and then push the button to make it happen, a CDU would also help. SS edit to add CDU I use a rotary switch to set the route and a (big meaty) Push Button to energise, if you use a three way four pole ther should be a spare pole to run your minic panel routing lights. Scissors are quite rare in prototype practice, some were used for loco release in terminal roads, (Oban) but more usually they are part way along a platform to allow portions of trains to be joined, Exeter Central, Snow Hill etc Scissors between up and down running lines is very much a model, especially fiddle yard, thing. Neat cutting work on the points., I did much the same with Code 100 a few years ago Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted June 8, 2014 Author RMweb Premium Share Posted June 8, 2014 My preferred method would be to have 3 push to make switches, one for each crossover and a centre one for normal linked to all 4 points. Looking at reversing the polarities of E & F for crossing over I am investigating using a double-poll-double-throw (DPDT) relay of some sort. Like this, I should be able to wire both motors into a single relay, so this would be fired by the switches from points 1 & 3 leaving 2 & 4 to take care of feeding G & H Dale, Link to post Share on other sites More sharing options...
chaz Posted June 8, 2014 Share Posted June 8, 2014 Chaz, I wouldn't be able to use the rotary switch with Seep motors as like the Peco motors they require a momentary toggle or push to make switch, for that to work I would have to use a tortoise motor or similar which I'm not sure I have enough room under the board for. Also the crossings at G & H vary in polarity depending which crossover is in use which is was provoked the though to leave them dead if both were set straight ahead. Dale Yes, you're quite right. One solution is the big* push button as mentioned by other posters - there are electronic solutions but these involve more complexity. A pity that you don't have room for Tortoises - these are an elegant solution and have several advantages, although they are expensive. *big - can handle high currents - I found Peco point motors fully capable of destroying one amp transistors when I was using these to switch routes. Had to resort to 2N3055 power transistors that will handle 5A. Link to post Share on other sites More sharing options...
Grovenor Posted June 8, 2014 Share Posted June 8, 2014 Scissors are quite rare in prototype practice, Not really, they went out of favour for a few years, and used to be common when layouts generally were more complex, but as a fairly recent example the Fenchurch St terminal approach consists of 5 scissors. Keith Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted June 8, 2014 Author RMweb Premium Share Posted June 8, 2014 I think I've sorted the polarity feeding with a couple of relays, Hope this is easy enough to understand. I can sort out the switch interlocking afterwards, feeding the correct polarity to each part was the biggest headache! Dale Link to post Share on other sites More sharing options...
micknich2003 Posted June 8, 2014 Share Posted June 8, 2014 Years ago, I had a similar problem, attached the track layout and the circuit diagram. I used minature relays to change the crossing polarity, the relays only being energized with the points reverse. Link to post Share on other sites More sharing options...
micknich2003 Posted June 9, 2014 Share Posted June 9, 2014 After yesterday's posting of the wiring diagram, I remembered, I still have the actual hardware. A couple of pictures attached, may be of interest to a few of you, it has lain gathering dust for over twenty years, possibly, I should blow off the cobwebs. Until this afternoon when I again looked at it, I didn't realise how much wire it had consumed. Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted June 9, 2014 Author RMweb Premium Share Posted June 9, 2014 Looks fantastic. I have been testing mine with a few trains if you see my layout thread. Dale Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted February 25, 2015 Author RMweb Premium Share Posted February 25, 2015 Evening, Thought I'd revive this topic rather than starting a new one. It is sort of to do with my scissors. I have now wired up most of my control panel but I'm a little stuck with how to get the LEDs for the scissors to work as I would like them. I am using points detection boards for my LEDs - described from post 149 in my layout thread - http://www.rmweb.co.uk/community/index.php?/topic/73981-dale159s-unnamed-layout-first-test-train-approaching/page-6 Here is what I've got so far, basically I'm looking for a way of suppressing the 4 straight ahead LEDs together as one when either of the two crossings are set but without setting both as this is prevented by interlocking on the panel due to the way the real scissors on the layout are wired As I've said in the layout thread I think the answer may lie in the use of transistors but I'm not sure quite how. Any ideas greatly appreciated Dale Link to post Share on other sites More sharing options...
Memphis32 Posted March 9, 2015 Share Posted March 9, 2015 Are the current limiting resistors fitted seperately, built in to the detector or leds? Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted March 9, 2015 Author RMweb Premium Share Posted March 9, 2015 Are the current limiting resistors fitted seperately, built in to the detector or leds? The detector boards were supplied with LEDs and resistors but I have used 12v LEDs bought from Rapid Electronics so no resistors required. Dale Link to post Share on other sites More sharing options...
Memphis32 Posted March 9, 2015 Share Posted March 9, 2015 Ahh. That scuppers my original plan then. I'll have a think tomorrow, once I have some paper to hand! Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted March 9, 2015 Author RMweb Premium Share Posted March 9, 2015 Ahh. That scuppers my original plan then. I'll have a think tomorrow, once I have some paper to hand! I thought maybe a set of 4 diodes 2 from each motor under the control panel, one from each going to each input on the detector board, although that has gone on the back burner while I deal with some of the other electrical issues I've got currently. Dale Link to post Share on other sites More sharing options...
RMweb Premium Clive Mortimore Posted March 10, 2015 RMweb Premium Share Posted March 10, 2015 Hi Dale With a scissors crossover you need to ensure all crossings are isolated, looking at your modified Peco point you will need to replace the metal fishplates with isolating plastic ones. Treat each point as a facing point so will need to be isolated from the one it is facing and have its own feed from the toe of the point. The crossings are already isolated. The wiring of the crossovers becomes easier when this is done. Common crossings C and H are wired to point motor number 3, likewise D and G are wired to point motor number 4. The "k" crossings E and F are always opposite poles to each other just treat these as a very short section of track and they require their own sectional power feed. Point motors number 1 and 4 are wired up so they work in tandem. Point motors 2 and 3 are wired up together. There are many ways to prevent both 1+4 and 2+3 being operated so they both form crossovers this will cause a short and would be a potential crash of trains. I find a clout round the back of the head of any operator who attempts this to be the cheapest and most effective means. Point crossings wired for straight running. When point motors 1 and 4 are reversed to form a facing crossover. When point motors 2 and 3 are reversed to form a trailing crossover. Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted March 10, 2015 Author RMweb Premium Share Posted March 10, 2015 Hi Clive, The scissor crossings on the layout are all wired in and working nicely - see my layout thread bottom of page 4. It is now a case of working out how to display what the scissors are doing in LEDs on the control panel once I've sorted my other electrical problems. Dale Link to post Share on other sites More sharing options...
Memphis32 Posted March 11, 2015 Share Posted March 11, 2015 Could you use seperate LEDs and resistors? It will make it much easier, and use a fraction of the components! Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted March 11, 2015 Author RMweb Premium Share Posted March 11, 2015 Could you use seperate LEDs and resistors? It will make it much easier, and use a fraction of the components! Well the good news is I've now solved the majority of the points problems but unfortunately not the scissors, could I use resistors with the existing 12v LEDS? Link to post Share on other sites More sharing options...
bike2steam Posted March 12, 2015 Share Posted March 12, 2015 Impressive, but looks like hard work, glad I took the easy way out, and used Shinohara scissor crossings, only draw-back being loco wheel back-to-backs have to be spot on. Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted March 12, 2015 Author RMweb Premium Share Posted March 12, 2015 Impressive, but looks like hard work, glad I took the easy way out, and used Shinohara scissor crossings, only draw-back being loco wheel back-to-backs have to be spot on. These can be a bit temperamental as well, especially with lighter vehicles. Heljan locos have performed best so far probably due to the sheer weight of them they just plough right through! Dale Link to post Share on other sites More sharing options...
RMweb Premium dale159 Posted March 12, 2015 Author RMweb Premium Share Posted March 12, 2015 A quick video I've just uploaded to YouTube Dale Link to post Share on other sites More sharing options...
BlackRat Posted March 12, 2015 Share Posted March 12, 2015 "This video is private" Link to post Share on other sites More sharing options...
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