Andy Reichert Posted July 6, 2015 Share Posted July 6, 2015 Andy, It should be no more difficult than operating with a single motor or double solenoid drive. Gordon A Bristol As you can see, It's "done" and inexpensively manufacturable, not "should" in my case. And the two movements are in orthogonal planes, of different lengths, yet self adjusting, and require no electronics or pre-programming. Having that as a DIY project for a dozen turnouts on layout is not likely to be just an evening's work with a few hand tools. Andy Link to post Share on other sites More sharing options...
AndyID Posted July 7, 2015 Share Posted July 7, 2015 I am intrigued by the assertion that raising the servo supply return voltage actually improves noise immunity, because in principle it should make it worse due to reducing the difference between the servo input threshold levels. Perhaps it is a result of effectively swinging the input pulse below the revised servo ground? Hi Gordon, I'm referring to the SG90 and any other servos that use the same control chip. The reason elevating the ground reference works is because the noise immunity in the low state is much less than the noise immunity in the high state. I created a test rig that would reliably couple sufficient noise into the servo's input to trigger the internal monostable when the input was held low. This did not happen when it was held high. When the ground was offset I could not trigger the monostable in either state. There is a question about whether or not this amount of reverse bias could damage the chip's input. My empirical testing indicates this is not a problem, but anyone who tries this method should understand that they are violating the nominal spec. for the chip. Cheers! Andy Link to post Share on other sites More sharing options...
Gordon H Posted July 7, 2015 Share Posted July 7, 2015 This would tie up with some motor current monitoring results performed on some analogue servos that have been discussed within MERG recently, whereby it is clear that the motor current only starts after the control pulse finishes (i.e. the negative edge), which is pretty obvious when you think about it, as the servo cannot 'know' that the latest pulse is longer or shorter than the last one until it ends. Anyway, shifting the input threshold by whatever means is likely to reduce the occurrences of spurious negative edges being detected, hence apparently improving the noise immunity. Link to post Share on other sites More sharing options...
Blue Max Posted July 7, 2015 Share Posted July 7, 2015 What he said ??? Link to post Share on other sites More sharing options...
AndyID Posted July 7, 2015 Share Posted July 7, 2015 This would tie up with some motor current monitoring results performed on some analogue servos that have been discussed within MERG recently, whereby it is clear that the motor current only starts after the control pulse finishes (i.e. the negative edge), which is pretty obvious when you think about it, as the servo cannot 'know' that the latest pulse is longer or shorter than the last one until it ends. Anyway, shifting the input threshold by whatever means is likely to reduce the occurrences of spurious negative edges being detected, hence apparently improving the noise immunity. To some extent, yes. But it's a bit more complicated than that. You'll find a description of how the chip in the SG90 works here - http://www.rmweb.co.uk/community/index.php?/blog/1780/entry-15751-servo-operation/ The problem isn't the detection of spurious negative edges; the problem is the detection of spurious positive edges that launch the internal monostable. If that happens, it is virtually guaranteed to produce an undesirable servo excursion. To make matters worse, if the external controller only sends position pulses to the servo while it is changing the servo's position, and a noise event happens to trigger the monostable while the controller is not sending position pulses, the servo will not return to the correct position after the excursion. Link to post Share on other sites More sharing options...
jasp Posted July 8, 2015 Share Posted July 8, 2015 Came across this system at the Perth show last weekend: http://loolee.org/megapoints/ Appeared to be very simple to use, on-board programming, route setting etc Plenty of on-line literature. I reckon I will use when my railway is (eventually) built Jim P Link to post Share on other sites More sharing options...
Andy Reichert Posted July 8, 2015 Share Posted July 8, 2015 Came across this system at the Perth show last weekend: http://loolee.org/megapoints/ Appeared to be very simple to use, on-board programming, route setting etc Plenty of on-line literature. I reckon I will use when my railway is (eventually) built Jim P I guess that's the (relatively) expensive electronics overhead I was seeing. At 50 UKP (plus power) for 12 points, that's 4 UKP Extra per point, for running servos that only cost (their quote) 1.40 UKP each without. OTOH, things like Arduinos are half that price, as are XP and earlier old PC's. Link to post Share on other sites More sharing options...
jasp Posted July 9, 2015 Share Posted July 9, 2015 Agreed Andy but for the electronically uninitiated a great device Jim Link to post Share on other sites More sharing options...
AndyID Posted July 9, 2015 Share Posted July 9, 2015 Agreed Andy but for the electronically uninitiated a great device Jim Hi Jim, I'm sure they are well designed and manufactured to a high standard, but I'm a bit concerned that some customers are going to be disappointed if their layouts/environments happen to produce a lot electrical noise. As far as I can see, the Megapoints website makes no mention of any means to mitigate the effect noise transients might have on the servos themselves. If they had a solution to this well known problem I'm sure they would make it a product feature. Hopefully they will offer a full refund to customers who are not delighted with their product. Cheers! Andy Link to post Share on other sites More sharing options...
bigal10 Posted July 12, 2015 Share Posted July 12, 2015 I can't lay claim to this method of mounting, I got the idea from Dave Fenton, he who is MegaPoints. I do think it's the least complicated I've come across. I like my motors hidden beneath the layout, and this works very well. It is a 50 mm section of 15mm x 15mm ally U section channel, bought from B&Q (sorry folks, in the UK) in 1m lengths for £5.90 or so, (also found in Wickes for only ££5.00) Following the MegaPoints video, drill 2 mounting holes near each end, and a small hole for the fulcrum. I use 1mm piano wire as the actuator, Z-bend to go through the cut-down horn, and once you've got the end-points of the servo set, trim off the excess above the track. 1mm piano wire is quite flexible, and allows a good hold of the blade against the stock rail. I am an ECoS user and have a mix of servo controllers, ESU, GFB, and am currently trialling MegaPoints. The picture shows an E-Sky servo, but I have some TowerPro, and more recently HobbyKing, both analog and digital, all of which are just a push (tight) fit into the channel. Regards, Alan Link to post Share on other sites More sharing options...
Andy Reichert Posted July 12, 2015 Share Posted July 12, 2015 Now that is a very ingenious, simple and effective mounting/pivot solution. Andy Link to post Share on other sites More sharing options...
RMweb Premium t-b-g Posted July 12, 2015 RMweb Premium Share Posted July 12, 2015 I can't lay claim to this method of mounting, I got the idea from Dave Fenton, he who is MegaPoints. I do think it's the least complicated I've come across. I like my motors hidden beneath the layout, and this works very well. It is a 50 mm section of 15mm x 15mm ally U section channel, bought from B&Q (sorry folks, in the UK) in 1m lengths for £5.90 or so, (also found in Wickes for only ££5.00) image.jpg Following the MegaPoints video, drill 2 mounting holes near each end, and a small hole for the fulcrum. I use 1mm piano wire as the actuator, Z-bend to go through the cut-down horn, and once you've got the end-points of the servo set, trim off the excess above the track. 1mm piano wire is quite flexible, and allows a good hold of the blade against the stock rail. I am an ECoS user and have a mix of servo controllers, ESU, GFB, and am currently trialling MegaPoints. The picture shows an E-Sky servo, but I have some TowerPro, and more recently HobbyKing, both analog and digital, all of which are just a push (tight) fit into the channel. Regards, Alan That is very neat and clever and is an idea that you may well find being nicked/copied by others, including me! Link to post Share on other sites More sharing options...
Gordon H Posted July 12, 2015 Share Posted July 12, 2015 How is the servo held in the bracket? Just friction? Looks like you have cut off one of the mounting tabs. Link to post Share on other sites More sharing options...
bigal10 Posted July 13, 2015 Share Posted July 13, 2015 As I said, not my original idea, it came from Dave Fenton, the owner of MegaPoints, I met him at the Preston Model Rail show in January, 2015. I would recommend all readers to have a look at the videos on the MegaPoints website. Yes, the servo is just a push-fit into the channel, and yes, one tab is romoved. That E-Sky servo in the photo is a VERY tight fit, but the HobbyKiing white ones are just right. Regards, Alan. Link to post Share on other sites More sharing options...
lyneux Posted July 17, 2015 Share Posted July 17, 2015 I have 40 servos to mount on my fiddle yard that I cam currently building. To that end, I got fed up with fabricating brackets out of aluminium angle and have produced a small etched mounting bracket to hold the servo plus a switch to change frog polarity etc. The switch is activated at one end of travel (I find this a very reliable technique). Switches can be stacked parallel if more than one is required (just need to solder a tag to join the levers together). They are designed to take the nice and cheap Tower Pro SG-90 servos (around £1.50 each on ebay). By mounting the servo horizontally they are very unobtrusive below the baseboard (about the size of a small matchbox placed rough-side to the board). I use these along with the ESU Switch Pilot Servo which both programs and drives the servos via DCC (can also be used in non-dcc mode with switches wired into them from a panel). All in, they come in at about £11 per point for a fully DCC controlled turnout! Photo below. If you are interested in these, then please PM me as I have ordered more than I need. Guy Link to post Share on other sites More sharing options...
Andy Reichert Posted July 17, 2015 Share Posted July 17, 2015 I'm definitely of the opinion that it's the availability of inexpensive and simple mounting hardware that is the key to making servo point operators viable from both a convenience and a cost standpoint. However I'm not convinced that the overall cost equation should only work if it requires other major costs to be amortized in as well. For example DCC control of turnouts is very much a minority preference here in the US, even though our popular "operations" philosophy expects the "train crew" to throw most of them as they arrive, instead of the UK culture of having a signal box and a signal man throwing the turnouts (as pre-set routes) separately from the train drivers. Andy Link to post Share on other sites More sharing options...
lyneux Posted July 17, 2015 Share Posted July 17, 2015 I'm definitely of the opinion that it's the availability of inexpensive and simple mounting hardware that is the key to making servo point operators viable from both a convenience and a cost standpoint. Agreed... I didn't have a spare 20 hours to knock up the brackets - hence used (meagre) brain to design an etch! I put together 12 of these in an hour last week! I can fit (and wire) 4 to the board in an evening (say about 3-4 hours). The attached shows an evening's work. The brackets cost £2.50 each (including bolts). Guy Link to post Share on other sites More sharing options...
RMweb Premium Ray H Posted July 17, 2015 RMweb Premium Share Posted July 17, 2015 I am hoping to use servos to control the points on my proposed layout and the control those servos using the limited wiring afforded by DCC. My plan is to use MERG accessory decoders to control the servos through MERG Servo4 boards. The accessory decoders will be linked to the accessory bus and that in turn will be linked to an NCE mini panel that will allow me to control the servos by switches/levers. It may seem a bit of a long-winded way to do things but it means that I can wire the whole layout with the minimum of wiring across baseboard joins as I intend to mount the servos, the PCBs and all connections (other than those to rails) on the front edge of the baseboards to avoid the need to either grovel under the layout to work on the wiring or to turn the baseboards over to do so. Link to post Share on other sites More sharing options...
bigal10 Posted July 18, 2015 Share Posted July 18, 2015 Hi Guy, (and guys), My aluminium channel mount costs £0.25 per 50mm (if you get it from Wickes) I have used SwitchPilot Extension on SwitchPilot Servo2, where I had to power a dead frog, and that was only because the Peco solder had come adrift, and I didn't want to destroy the point. Admittedly, ESU's kit are not always the cheapest, but they do work very well, and allow you program and adjust the throw etc., from your control position. - And, if I was to wire the frog of each of 4 points, the total cost for 4 servo operated points using my channel and Hobby King servos, would be, SWPS2 = £25, SWPEX = £25, 4 x servo = £6, 4 x channel = £1, plus 4 bits of piano wire, and a couple or 3 hours of my time, at old-farts rate =£0, Total = £57.00 Result, a few pleasant hours in the loft, and nicely operating points. Each to their own, and it's great to see on these pages how people approach problems, and find solutions. Regards, Alan. Link to post Share on other sites More sharing options...
RMweb Premium CloggyDog Posted July 20, 2015 RMweb Premium Share Posted July 20, 2015 I haven't looked at MERG's lines lately. I didn't realize they had moved into mechanical bits and pieces. OTOH, hand crafting this to operate year in, year out, from just one servo would likely take the sort of effort and complicated set-up that I'm talking about. Andy There is an 'RTR' solution from Germany. H0fine.de have a selection of point mechanisms including a rotating lantern (as German pointwork has a rotating lantern indicator) point throw and lantern: http://www.h0fine.com/shop/product_info.php?products_id=68 lantern only: http://www.h0fine.com/shop/product_info.php?products_id=23 (there's also one with inbuilt switch and a self-contained servo version) Could be adaptable to US-type switch machines? Link to post Share on other sites More sharing options...
Gordon A Posted July 20, 2015 Share Posted July 20, 2015 I agree with Alan (Bigal 10) in that I have used the Switch Pilot Servo and am very satisfied, especially in the DCC mode. The Switch Pilot Servo is / was £26 for a four servo interface, which works at £6.50 per servo. Where a single servo interface is needed I have tried examples from Wizard Models and Heathcote Electronics. The Heathcote Electronics version is less than £10 for a single interface, allows for speed and angle of throw adjustments, but does not have a bounce facility for signals. Although the Wizard Models does have a bounce facility, it does not have the current output required to drive the larger Hi-Tec servos I use that the Heathcote Electronics version does. Gordon A Bristol Link to post Share on other sites More sharing options...
Andy Reichert Posted July 20, 2015 Share Posted July 20, 2015 There is an 'RTR' solution from Germany. H0fine.de have a selection of point mechanisms including a rotating lantern (as German pointwork has a rotating lantern indicator) point throw and lantern: http://www.h0fine.com/shop/product_info.php?products_id=68 lantern only: http://www.h0fine.com/shop/product_info.php?products_id=23 (there's also one with inbuilt switch and a self-contained servo version) Could be adaptable to US-type switch machines? Interesting. Great minds! I've already done that in a similar way, but I went for stainless steel for longevity and low cost. It's the pending Mk II version of the Mole Point motor. I went the other way and started with the powered version first. Lots of other new animation applications coming for that sort of tech I suspect Interesting site. Looks like he has his own version of my US tie plates and Bill Bedford's grab iron wire bender. Andy Link to post Share on other sites More sharing options...
Grovenor Posted July 20, 2015 Share Posted July 20, 2015 Interesting. Great minds! I've already done that in a similar way, but I went for stainless steel for longevity and low cost. It's the pending Mk II version of the Mole Point motor. I went the other way and started with the powered version first. Lots of other new animation applications coming for that sort of tech I suspect Interesting site. Looks like he has his own version of my US tie plates and Bill Bedford's grab iron wire bender. Andy Andy can find them closer to home than that! http://www.rapidotrains.com/railcrew.html Keith Link to post Share on other sites More sharing options...
RMweb Premium njee20 Posted July 20, 2015 RMweb Premium Share Posted July 20, 2015 I have one of the MegaPoints controllers, not actually installed yet, but was playing with it t'other day, and by using splitter cables it will happily throw 4 servos from a single output, so whilst the headline £50/12 turnouts seems a lot, in reality if you've got pairs of points or scissor crossings that tumbles quite quickly, frankly into SEEP territory, and vastly cheaper than any other slow-motion motors. That said I'll probably now find I get horrendous 'noise' and it'll all be ripe for the bin! Link to post Share on other sites More sharing options...
bigal10 Posted July 20, 2015 Share Posted July 20, 2015 I have recently installed a couple of IMP Digital Servo Controllers from GFB Designs. They can operate solely from the DCC bus, or DC with a switch, and each control one servo, which is handy for a remote situation, where you don't want lots of wires. They can be set to operate points, or, a new feature, semaphore signals, with bounce! And all for £12.10 ! "......no connection with the company, just a satisfied customer......" You know the drill. Regards, Alan. Link to post Share on other sites More sharing options...
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