Servo Control of Points

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John Bateson
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Servo Control of Points

Postby John Bateson » Sun Jan 06, 2013 3:19 pm

It's about time I replaced the point motors on my layout.
I've been looking at Tortoise (imports from the USofA) seem to come out at about £9.00 each for a batch of 12. Under £100 may avoid any customs duty ...
These would fit my existing wiring quite easily.
However, I suspect that Servos are the way to go and since the Tower Pro Micro Servo (seen on Highland Miscellany) at £2.31 each appeals to the miser in me, perhaps they would be a good buy. And they seem small enough so that they would fit into a constricted area.
But what else do I need - I have enough bits to go fully DCC now and make use of presents received some years ago.
John
Slaving away still on GCR stuff ...
Avoiding the soaps ...
http://www.greatcentralmodels.co.uk

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Sun Jan 06, 2013 5:06 pm

John, When you say "Fully DCC" what do you really mean?
Do you want to operate the points from a DCC hand controller?
I find that a very cumbersome process.
if you want to operate from a frame or panel then there is not much point in doing it via DCC, you have to find some module to put the switch/lever info into the DCC system and then decoders to take it out again. It only seems worthwhile to me if you want to involve a computer and have an on-screen panel.
If not very careful all of this can quickly erode the cost benefit of the servos.
Regards
Keith

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John Bateson
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Re: Servo Control of Points

Postby John Bateson » Sun Jan 06, 2013 7:18 pm

Keith,
I agree that operating points from a hand controller would be cumbersome. I want to differentiate driving from signalling.

I think I can drive the signalling from within JMRI using a laptop. I just don't have the full knowledge that would make that something easy to do.
Drivers will drive and obey using their own hand controllers! This will be an NCE system with the SB5 booster.

There are 4 power districts and the geography of these is variable - switched by the signallers defining the route. There should normally be only one locomotive on any one route anyway.

IMG_0022.JPG
The route logic - relay driven rated all at 2 amp
I also have a 35 way rack which it would be nice to add in later.

IMG_0020.JPG
And the society lever frame

IMG_0021.JPG
The routes - 4 main with a headshunt
Slaving away still on GCR stuff ...
Avoiding the soaps ...
http://www.greatcentralmodels.co.uk

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Sun Jan 06, 2013 7:50 pm

I am running points and signals from JMRI but using CBUS rather than DCC. CBUS has the facility for feedback as needed and can cope with external panels/leverframes as well as the PC so worth a look. Its easy enough to use DCC accessory decoders to work the servos via DCC from JMRI but a bit trickier to get much beyond that with the DCC alone.
How are you aiming to do the frog switching? If using relays for that then a spare contact can be used for the servo4.
If you are planning microswitches in the mechanics then CBUS can eliminate the servo4 and run the servos directly as we have a board that will run 8 servos.
Lots of options here to look at.
Keith

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steamraiser
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Re: Servo Control of Points

Postby steamraiser » Mon Jan 07, 2013 11:45 am

I have used an ESU Switch Pilot (ESU 51802) to drive servos on Newbridge Sidings using DCC.
The unit can drive up to 4 servos either from a DC or DCC sourse. No seperate decoders are required for DCC operation.
I consider that a cost of £26.00 for a DCC interface between my DCC controller and 4 R/C servos a good deal.
The ESU unit allows you to adjust the travel / throw of the servo and the speed.

Gordon A
Bristol

Alan Turner
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Re: Servo Control of Points

Postby Alan Turner » Mon Jan 07, 2013 1:29 pm

As an alternative to the MERG Servo4 or the CBUS CANSERVO have a look at the SERVO1 from MERG. It provides a mounting for the servo and has an output to switch a relay for crossing polarity control.

It can be controlled from CBUS or with a simple switch.

Regards

Alan

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Mon Jan 07, 2013 3:30 pm

John,
Just a thought as its not mentioned, most of your points are crossovers, its simple to drive both ends from one servo which helps cut down on the electronics. All mine are done that way except for a couple where the two ends are on different boards.
Regards
Keith

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Mark Tatlow
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Re: Servo Control of Points

Postby Mark Tatlow » Mon Jan 07, 2013 8:56 pm

John,

Sorry I have been slow in replying.

You need two things to complete your set up and use of servos. A means of connecting the servo to the turnout (for signals you will see that i have made this an extension of the signal base) and a means of controlling the servo.

There are several proprietary mounts:
CD3D do one (http://cd3d.co.uk/2012/10/07/the-new-mu ... trol-wire/),
MSE do one (http://www.wizardmodels.co.uk/FrameSetS ... M=wizabout)
and MERG do one for their members - I can not post the link but it is rather cheaper but requires you to do more assembly.

As an alternative, you can make these:
029compress2.JPG
029compress2.JPG (37.92 KiB) Viewed 8635 times

All of these have microswitches to control crossing polarity.

I have presently not used servos for turnout control but probably will for my next venture. I think I will be with Keith in that straight control via DCC is a bore and it does not really work with a mechanically interlooked frame which is also on the agenda. I will either stay with the simple servo control operated by microswitches on the lever frame or I will go down CBUS also operated from microswitches on the frame. CBUS is a bit of electronics that picks up a signal from an activator (in this case a microswitch) and codes that as a message which it sends down a pair of wires. There is then another bit of electronics that decodes that message and decides to send it to another device (in this case the servo) to tell it to do something. It reduces interconnection wiring, but not the local wiring at the servo or lever frame

If you want plain servo controllers (ie without CBUS); then you have the choice of at least the following:

- MSE (http://www.wizardmodels.co.uk/FrameSetS ... M=wizabout)
- The Bouncer (http://www.copnor.enta.net/FS/The%20Bou ... Manual.pdf) - I am not absolutely certain this is still in production?
- Borg Rail (http://www.borg-rail.co.uk/)
- MERG (http://merg.org.uk/index.php - but members only for purchases)

Hope this helps.
Mark Tatlow

sebring115
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Re: Servo Control of Points

Postby sebring115 » Fri Jan 13, 2017 11:15 pm

Just looking at using servos to control points and also frog polarity. Anyone heard of these http://www.blocksignalling.co.uk/index. ... controller or have any recommendations

Cheers

Mark

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Sat Jan 14, 2017 11:00 am

Depends whether you just want to buy ready made or you can assemble printed circuit boards, with good instructions and support.
For the price of one of their Servo controllers you can join MERG. buy a servo controller kit, and have change. By the time you need a second controller you are way ahead.
Regards

junctionmad
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Re: Servo Control of Points

Postby junctionmad » Sun Jan 15, 2017 12:16 am

John Bateson wrote:Keith,
I agree that operating points from a hand controller would be cumbersome. I want to differentiate driving from signalling.

I think I can drive the signalling from within JMRI using a laptop. I just don't have the full knowledge that would make that something easy to do.
Drivers will drive and obey using their own hand controllers! This will be an NCE system with the SB5 booster.

There are 4 power districts and the geography of these is variable - switched by the signallers defining the route. There should normally be only one locomotive on any one route anyway.

IMG_0022.JPGI also have a 35 way rack which it would be nice to add in later.

IMG_0020.JPG
IMG_0021.JPG



nice lever frame, i need a 62 lever version !!

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Sun Jan 15, 2017 10:52 am

John Bateson in 2013 wrote:There are 4 power districts and the geography of these is variable - switched by the signallers defining the route.

Reread this thread since it has been re-activated, picked up this which I must have passed over the first time.
But this does seem to be bringing a DC technique through into DCC and thus creating complexity for no benefit. Did you actually do this and why?
Regards

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John Bateson
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Re: Servo Control of Points

Postby John Bateson » Sun Jan 15, 2017 11:33 am

Did you actually do this and why?

Yes.
I am one of the Luddites who believes that connecting all the lines in parallel is wrong headed and potentially dangerous, it means that one short stops everything. It also needs proper power capability - hence a booster - expensive. Doing this sort of thing makes it impossible for a simple controller to take over the whole layout, a booster is needed. And my pension fund started to cringe.

And if you add up all the options for switching frogs it was only marginally less complex than the base design. I cringe when thinking about leaving this to a switch under a point motor, so I insist on the switch being back in the control box. It also meant I could properly connect suitable SWG wire! Too many people under resource the cabling. Which is why all my track cable is/was 16/.07.
My days of soldering underneath a baseboard are long past.

Back in my work days I was involved in a team in building a a pre-processor thingy for scientific work, very clever stuff but nobody did the power and cabling specs for the lot (too boring it was) - but it was a rated 5Kw worth in a single 6' cabinet. So who made himself unpopular and then got stuck with the cabling and ventilation design! Since then I have been even more keen about cabling for worst case scenarios. Probably also due to my RAF engineering days.

While I still have the baseboards concerned, working in the attic is now very difficult so it has all been abandoned. Still waiting for the design muse to strike for the new hobby room in the garden.

Felling especially grumpy :cry: today as well.
And don't get me started on 'stubs' for DCC... :evil:

John
Slaving away still on GCR stuff ...
Avoiding the soaps ...
http://www.greatcentralmodels.co.uk

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stephenfreeman
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Re: Servo Control of Points

Postby stephenfreeman » Tue Jan 17, 2017 8:39 am

Personally I don't like using a DCC hand held controller for doing anything other than controlling locos. So good old analogue switches work for me but so does using DCC with JMRI's Panelpro.

The only reason for using multiple Boosters is IMHO where the size of the layout warrants it. You can still split up the layout into different power districts which can be switched in or out with, yes a switch, or if you prefer by a circuit breaker such as that made by Tam Valley, so not all of a layout need be affected by a short.

Tam Valley also do a useful gadget called a Hex Frog Juicer, which will do all the switching of crossing polarity for you automatically for up to 24 vees (cost currently £71.00 from Coastal DCC)
Stephen Freeman
Bespoke Finescale Trackwork and Semaphore Signals 7mm to 4mm scales
https://www.tracknsignals.co.uk

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Colin Parks
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Re: Servo Control of Points

Postby Colin Parks » Tue Jan 17, 2017 11:18 pm

Re.Hex frog juicers, this a control component that I have researched recently.

The deal breaker for me, and unless I have misunderstood the data sheet available online, is that using a frog juicer to control a crossover without a section of plain tack in between the turnouts is not possible. From the diagram, it is evident that if a large loco, steam or diesel/electric passes across two crossings as it traverses a crossover, the juicer would be unable decide which polarity to change to. This could cause the system to stall. See page two here:

http://www.tamvalleydepot.com/images/He ... 1_5_2p.pdf

The solution would be near impossible to implement on a crossover with a British standard 6ft way. (My Templot design has the crossings at approx 110mm centres on a B8 crossover.) Tandems and double slips would also be similarly problematic and in any case, the solution proposed by the Tam Valley manual requires unprototypical joints and extra sections between crossings in such a situation.

I would really liked to hear that I am wrong in thinking this to be the case, as I really would have preferred to have used a frog juicer on my so-called test track, to avoid all those micro switches!

Colin

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Martin Wynne
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Re: Servo Control of Points

Postby Martin Wynne » Wed Jan 18, 2017 12:15 am

Colin Parks wrote:to avoid all those micro switches!

Hi Colin,

Installing and maintaining adjustment of micro switches will drive you mad. They are the invention of the devil.

The answer is and always has been relays. Small "sugar-cube" changeover relays are inexpensive nowadays. They can be banged in place anywhere convenient under the baseboard with a hot glue gun in seconds. And once there and wired up for crossing polarity switching they are truly "fit and forget" for the life of the layout.

To switch them you can slave them with a diode across a Tortoise motor, or if using mechanical control a simple reliable on-off switch is easily made using a brass screw and bit of springy wire. Much easier than making a changeover switch, and contact quality won't affect loco running.

regards,

Martin.
40 years developing Templot. And counting ...

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Jol Wilkinson
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Re: Servo Control of Points

Postby Jol Wilkinson » Wed Jan 18, 2017 8:43 am

Martin,

correctly fitted and set up, micro switches can be very reliable. That's why they are used in industrial applications.

If using to servos as point motors how are you going to control relays? Some sort of switch will be required. It may be possible to take a feed from the control panel switch to the servo controller to activate the relay. If not, then I suggest micro switches are the best under baseboard solution.

Tortoise and Cobalt point motors include switching, so while they seem expensive initially the convenience they provide may be considered worthwhile.

Jol

sebring115
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Re: Servo Control of Points

Postby sebring115 » Wed Jan 18, 2017 10:24 am

Finally ordered one of these as I dont get enough modelling time let alone to get into Merg electronics.

http://www.blocksignalling.co.uk/index. ... controller

Good thing is, the board has wiring for relays to control the frogs.

Cheers

Mark

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Wed Jan 18, 2017 10:34 am

If using to servos as point motors how are you going to control relays?

The siple way is to use the lever/switch to operate the relay and use one contact set on the relay for the crossing switching and the other contact set to control the servo driver.
Regards

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Colin Parks
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Re: Servo Control of Points

Postby Colin Parks » Wed Jan 18, 2017 11:14 am

It sounds like a micro switch uses the least amount of wiring and can be local to the crossing which it controls. The notion of relays sounds appealing, but seems to add another layer of complexity if they themselves need switches.

I am still thinking about Frog Juicers, more wishful than anything else as it would be a simple fix. The track formation I am working on at present contains two crossovers including one tandem turnout and there will be three crossovers if I ever get that far. One other concern with these juicers is that it would appear that there is a potential for a loco to be driven over a wrongly set turnout in the trailing direction -or am I misunderstanding something about the circuitry?

Colin

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Martin Wynne
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Re: Servo Control of Points

Postby Martin Wynne » Wed Jan 18, 2017 11:46 am

grovenor-2685 wrote:The simple way is to use the lever/switch to operate the relay and use one contact set on the relay for the crossing switching and the other contact set to control the servo driver.

Hi Keith,

That requires a double-pole relay which tends to be a bit more expensive. How are servos controlled? If it is a simple 5V on-off you could use the same line switched from the layout ground. If you need a pull-up resistor, the relay could be exactly that. Relays are readily available for 5V. Put a quench diode across it if using it as a resistor.

These are 12V. £1.49+vat post free: http://uk.rs-online.com/web/p/non-latch ... s/7933777/

How much is a frog juicer?

For more discussion on this subject see: viewtopic.php?p=34886#p34886

Having to adjust a micro-switch underneath a baseboard is a cruel punishment in contravention of the Geneva convention. Image

regards,

Martin.
40 years developing Templot. And counting ...

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Wed Jan 18, 2017 12:19 pm

Martin Wynne wrote:Hi Keith,

That requires a double-pole relay which tends to be a bit more expensive.

but not significantly so, the relays I use are less than £1 each although you do need to add a bit of stripboard to mount them on
How are servos controlled?
Normally with a servo control board that will need a simple on/of contact to trigger it. Some people do hack the servos by removing the electronics so it is just a geared motor, but then you lose the speed and position control given by the electronics.
If it is a simple 5V on-off you could use the same line switched from the layout ground. If you need a pull-up resistor, the relay could be exactly that. Relays are readily available for 5V. Put a quench diode across it if using it as a resistor.
its not a 5V on/off so this is irrelevant complication.
How much is a frog juicer?
A lot more than a £1 relay :)

Having to adjust a micro-switch underneath a baseboard is a cruel punishment in contravention of the Geneva convention. Image

I do use microswitches where I have manual point operation, and they are under the board, but all adjustment is done with the board turned upside down.
regards,

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Jol Wilkinson
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Re: Servo Control of Points

Postby Jol Wilkinson » Wed Jan 18, 2017 3:24 pm

Martin Wynne wrote:
Having to adjust a micro-switch underneath a baseboard is a cruel punishment in contravention of the Geneva convention.



Probably less so than setting up one of those servo controllers that has it's switches, pushbuttons, control LEDs, etc. mounted on it, rather than the excellent MERG remote control box system.

And if the adjustment for the micro switch is correctly designed, it should be easy to adjust. But if properly designed it shouldn't need regular adjustment anyway.

I've only once had to adjust one of the micro switches on the original bit of London Road (built over thirty years ago) since I bought it. However, don't ask me about my experience with servo systems.

Jol

Lindsay G
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Re: Servo Control of Points

Postby Lindsay G » Wed Jan 18, 2017 7:44 pm

Might an L293D be an alternative to the relay for changing points polarity? Via an Arduino, I've been playing with them as a means of reversing polarity on a turntable - but not to the stage of using them in anger.

Lindsay

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grovenor-2685
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Re: Servo Control of Points

Postby grovenor-2685 » Wed Jan 18, 2017 8:43 pm

Perhaps, but then it costs twice as much as a relay and you will need a few more parts to go with it.
Sometimes simplicity is best.
Regards


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