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Old 01-01-2011, 12:12 PM   #1
Richard
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Question Turnout polarity switching with ESU Servo Motor

After a lot of internet searching I am closing in on a possible solution for turnout control on my planned N-gauge layout. It will have about 12 turnouts, but I never say never so that could change.

I have an NCE Powercab starter set which has enough power to drive all the locos I will use but probably not the turnouts as well. I plan to use the Lenz LS150 Point Decoder, because it has 6 outputs and can control twin-coil and motorized switch machines. I plan to use Seep PM1 Point Motors with Built-In polarity switch and/or ESU Servo Motors. I like the latter, although there is about a £9 increase in cost per turnout, because they seem easier to fit and are more positive.

My question is, if I use the ESU Servo Motors, what would be a suitable way to achieve the polarity switching? I imagine it could be achieved with micro switches but would welcome any comments, especially on experience with the use of the above.
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Old 01-01-2011, 04:47 PM   #2
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Hi
I cant coment on ESU servos as I havent seen them or know anyone that uses them.
However if youre planning to use DCC for point operation, then have you considered using slow motion point motors? There are two the currently that have either built-in decoders or the decoder is available seperatly and both work extreamly well.
Look at the Traintronic TT300 or the DCC Concepts Cobalt motor working with a AD1 or AD4 decoder.
Examples....
Traintronic TT300
Cobalt motor and decoders
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Old 02-01-2011, 08:28 PM   #3
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I have considered the Cobalt motors but decided against them initially because of their size (approx 1.75 x 1.25 x 2.125 in) compared to that of the ESU servos (which are approx 1 x 1 x 0.5 in). These would be minimum dimensions as the mountings and movement mechanisms have to be considered for both. The ESU servos are also similar to R/C servos which I use in my other life (radio controlled model aircraft) so I know that the power to weight ratio would be more than adequate. Also, they would be slow acting, similar to the Cobalt motors although I have never seen either working.

I didn't come across the Traintronic motors in my initial research but, having now looked for them, I think they seem to be of a similar size to the Cobalt motors - I couldn't find any exact dimensions so I'm only going by illustrations.

I will bear your suggestions in mind though and thank you for your input.
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Old 08-01-2011, 12:53 PM   #4
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Question

If I use the Lenz LS150 Point Decoder I obviously need an AC power supply. The Lenz TR100 would seem to be suitable based on its spec (output 15V AC at 3 amps) but there are undoubtedly others. Would I need one such power supply for each decoder or could one supply two or even more decoders based on the assumption that at any one instant only one point will be operated (unless I get ambitions and use macros to change a number of points). Suggestions about other suitable power supplies would be most welcome and I am aware that the LS150 instructions (which I downloaded and think I understand) state that a 10 ohm resistor must be used to limit the current taken by the decoder.

As for the turnouts, I am tending towards using a servo motor as they seem quieter and more gentle on the turnout mechanism. Iím just going to have to splash the cash and get one to play with, together with a solenoid motor (probably Peco 10E). However, I have to get the decoder and power supply combination sorted out before I can do any serious playing.
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Old 08-01-2011, 06:51 PM   #5
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Hi Richard.
You should be able to use one PSU to feed all or certainly a large amount of the LS150 accessory decoders.
So long as you dont try to operate several solenoid point motors all at once.

Though slow motion and even servo motors will only draw a few milliamps each so several can be operated together if wished.
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Old 26-01-2011, 10:44 PM   #6
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I thought I'd provide an update just in case anyone else is thinking of going the same way.

I bought a SwitchPilot Servo which can operate 4 RC type servos simultaneously. I have the ESU servo mentioned previously, 2 RC servos (25 x 25 x 12 mm) which cost £5 each and a Futaba servo from my RC aircraft stock.

My NCE PowerCab allows me to set up macros to control all the servos together and also to monitor the current drain.

With one engine (Fleischmann 7000 tank) circulating the track and 4 servos all moving together the current drain is about 200 mA. At the moment I'm just using track power, the PowerCab limit being 2A.

I'm looking at the SwitchPilot Extension to do the frog polarity switching as this seems less hassle than using microswitches.
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Old 27-01-2011, 11:31 AM   #7
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Hi Thats some good current readings!

One thing to be cautions of and especially where DCC is used, is that the frog polarity change-over device doesn't operate too quickly, that is it has flipped the polarity while the actual point blades are still or partially closed and haven't fully moved over, as a short will occur at the frog!

This can be overcome by making the points so called 'DCC Friendly' (not a term I particularly like, but it seems to have become more accepted for what the conversion actually does). This is where the closure rails have insulating gaps in them and the two closure rails and their adjacent switch rails are bonded together on the pivot side of the gap, so as each closure rail is linked to its mating stock.
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Old 27-01-2011, 08:37 PM   #8
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I've read about that technique in several places but have nightmares about doing it because of the possibility of wrecking the points - particularly with N-gauge. I should try it on some old points (actually set-track points) which are not in good enough condition to use.

However, having downloaded the manual for the SwitchPilot family (which is translated in a slightly 'quaint' German style in places) and spent many hours poring over it, I think the SwitchPilot Extension, in conjuction with the SwitchPilot Servo, can achieve the same by switching a relay when the servo is commanded. CVs in the SwitchPilot Servo can control the end positions of each servo, the travel time from each position and also the delay before the relevant relay in the Extension switches. Thus, with a bit of fiddling with CV values, the polarity can be made to switch when the point blades are in mid travel.

Also, if I understand the manual correctly, the relays are DPDT, bi-stable (at least that's what the manual says) so hopefully I can use the other contacts to switch LEDs on a mimic diagram.

At £25 a pop for each unit (SwitchPilot Servo and Extension) £50 to operate a set of four points (in addition to the cost of the points) seems a bit much but long term I think it's a better bet as it saves fiddling around mounting and adjusting lots of micro-switches. Only time will tell and I only plan to have about 12 points in total - at the moment!
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Old 28-01-2011, 02:12 AM   #9
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Hi Richard,

Have you had a look at the MASTERswitches produced by DCC Concepts. I'm using them in conjuction with Seep PM1 motors to control frog polarity and provide LED connections for my control panel. http://www.dccconcepts.com/index_fil...sterswitch.htm
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Old 29-01-2011, 06:43 PM   #10
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Thank you for the link, I've had a quick look and will now download the manuals and have a more thorough read. They look very interesting and may be just what I want.

I thought I'd found most of the solutions but somehow I missed these completely.
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