Servo Controlled Points

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GAP
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Servo Controlled Points

Post by GAP » Sat Mar 06, 2021 2:29 am

I saw this project on Trainelectronics by Dave Bodnar http://trainelectronics.com/Servo-simpl ... /index.htm



Having one of the servo testers and some servos I decided to see if I could adapt it to my outside layout.

I have made a mock up of the controller and after a bit of experimenting in the shed with a test bed I put 2 servos out on the layout next to 1 set of LGB points and 1 set of Aristocraft points to see how they will go when I run a train through them.

If successful I will convert all my points to servo control.

I plan to put the controllers into a weatherproof enclosure and put a signal box over the top to disguise it.

My biggest worry was that the distance between the points I want to control and the controllers might be too large and the signal would degrade.

I made a 12 Ft long test cable and successfully changed a set of points over that distance.

As I have 2 signal boxes I will split the 12 sets of points I have into groups of 2 (6 controllers in each signal box).

The control switches will be weatherproof ones and mounted in enclosures with a lid.

Edit;

As the servo tester has outputs to control 3 servos at the same time, I have come up with the idea of using a second servo to move a semaphore signal so I can see which way the points are set at a glance.

I tested the idea on my bench set up and the second servo moved in time with the point driver.


Pictures of my test set up.
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Re: Servo Controlled Points

Post by philipy » Sat Mar 06, 2021 8:26 am

Looking good, well done.
It's very satisfying when you get it to do what you want, isn't it?

Rik has written comprehensively about his installation on Peckforton, and Greg and Tom have written about theirs. I detailed my own points and signals operations on these two threads.
https://gardenrails.org/forum/viewtopic ... 0&start=30
https://gardenrails.org/forum/viewtopic ... os#p138211

Maybe some ideas for you in some of those.
Philip

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Re: Servo Controlled Points

Post by GAP » Sat Mar 06, 2021 8:06 pm

That looks real good in the video.

I was considering running control rods similar to what is in the video but thought it may be a bit much to stretch them up to 12 Feet long.

Out of curiosity and because they may come back into play what did you use for the control rods?
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Re: Servo Controlled Points

Post by philipy » Sat Mar 06, 2021 8:56 pm

GAP wrote: Sat Mar 06, 2021 8:06 pm That looks real good in the video.

I was considering running control rods similar to what is in the video but thought it may be a bit much to stretch them up to 12 Feet long.

Out of curiosity and because they may come back into play what did you use for the control rods?
I used 2mm( I think) brass rod. Its OK over my relatively short runs, but I agree, at 12ft you'd certainly have expansion & contraction problems, especially in your summers. Plus, even if you could fit enough compensators to deal with that, I think you'd find that cumulative friction resistance and slop in the joints would be a problem.
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Re: Servo Controlled Points

Post by GAP » Sat Mar 06, 2021 9:22 pm

philipy wrote: Sat Mar 06, 2021 8:56 pm
GAP wrote: Sat Mar 06, 2021 8:06 pm That looks real good in the video.

I was considering running control rods similar to what is in the video but thought it may be a bit much to stretch them up to 12 Feet long.

Out of curiosity and because they may come back into play what did you use for the control rods?
I used 2mm( I think) brass rod. Its OK over my relatively short runs, but I agree, at 12ft you'd certainly have expansion & contraction problems, especially in your summers. Plus, even if you could fit enough compensators to deal with that, I think you'd find that cumulative friction resistance and slop in the joints would be a problem.
I thought the long length would be a problem, I am more comfortable with electrical wiring than mechanical methods so wiring it will be (maybe)
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Re: Servo Controlled Points

Post by gregh » Sun Mar 07, 2021 8:13 am

That looks like a nice easy solution. Hobbyking used to have cheaper little testers but it seems they are only selling the ones you tried.
I'd suggest only using the larger servos and not the little blue ones outside. I have used 2 of the bigger, normal ones outside for >15 years just housed in styrene covers. But I used the little blue ones for my signals, in small styrene enclosures, and they lasted only a few years.
Keep us up to date with your progress.
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Re: Servo Controlled Points

Post by philipy » Sun Mar 07, 2021 8:48 am

You could do a kind of half and half. Position your servos in a shed, ballast bin, pile of sleepers or whatever, a short distance from the point , working it with rodding from there and dummy rodding running back to the signal box.

This shows one of my servos under a dummy pile of old sleepers ( you'll have to excuse the winter lodgers of wood lice and small slugs!)
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It's one of the small blue ones that Greg mentiond and has been outside for 2 winters so far. I think it is still working but hasn't been tested since last autumn!

There should be a dummy manual point lever just in front of the sleepers, but that seems to have gone off on a winter holiday somewhere. :lol:
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Re: Servo Controlled Points

Post by Jimmyb » Sun Mar 07, 2021 1:56 pm

Graham, I do like this idea, I currently have T.E. but when I do away with track power (hopefully this year) I will need an alternative for my points :)

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Re: Servo Controlled Points

Post by Phil.P » Sun Mar 07, 2021 4:37 pm

However you drive the servos, you will need power, as well as control..

Tenmille do a point-rodding system..

In the real-world, coubter-weights are used, along with wire-cable for long runs.


All food for thought?

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Re: Servo Controlled Points

Post by GAP » Sun Mar 07, 2021 8:14 pm

Power will not be a problem, I am planning a 12V & a 5V bus around the layout with the voltage supplied by a 12V Sealed Lead Acid battery trickle charged by a solar panel. The 5V comes from one of these Buck Converters https://www.ebay.com.au/itm/281296554356

I am looking at these servos because of the metal gears which may make them a bit more robust. https://www.ebay.com.au/i/224143282848?ul_noapp=true

I am now planning to have the controller in a weatherproof enclosure with the servo mounted under the roadbed with the switches mounted on one panel.
The only thing going into and out of the enclosure will be the power feed and the switch wires, I can use multi wire sheathed cable so only 1 hole in the enclosure.

The next consideration will be condensation so waterproofing the servos may be a better option along with ventilation.
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Re: Servo Controlled Points

Post by gregh » Mon Mar 08, 2021 6:46 am

Don't forget that if you direct couple the servo to the points, you won't be able to operate them by hand. No just walking up and flipping them across - you'll have to walk back to the control panel.
I solved it with my picaxe servo control system by having a neutral (or rest) position for the servo, and a slotted drive connection to the points. It would be interesting to see if you could add another resistor and switch to the servo tester circuit to achieve the same idea.
Greg from downunder.
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Re: Servo Controlled Points

Post by GAP » Mon Mar 08, 2021 8:19 am

gregh wrote: Mon Mar 08, 2021 6:46 am Don't forget that if you direct couple the servo to the points, you won't be able to operate them by hand. No just walking up and flipping them across - you'll have to walk back to the control panel.
I solved it with my picaxe servo control system by having a neutral (or rest) position for the servo, and a slotted drive connection to the points. It would be interesting to see if you could add another resistor and switch to the servo tester circuit to achieve the same idea.
I know that I will not have manual control once this is done, it is a sacrifice I am prepared to make at this stage.

That is why I am adding signals to show which way the points are set. They will be just simple semaphore ones like you had at "Black Wall".

As for another switch, the ones I am using are double throw single pole so there is a spare pole already, but now I have this idea in my head that I can think about.

This is a block diagram of what I am doing; the solar panel and battery are here so I can start installing/mounting them while I wait for the other bits to arrive (controllers buck converter servos etc)
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Re: Servo Controlled Points

Post by GAP » Mon Mar 08, 2021 10:10 am

gregh wrote: Mon Mar 08, 2021 6:46 am Don't forget that if you direct couple the servo to the points, you won't be able to operate them by hand. No just walking up and flipping them across - you'll have to walk back to the control panel.
I solved it with my picaxe servo control system by having a neutral (or rest) position for the servo, and a slotted drive connection to the points. It would be interesting to see if you could add another resistor and switch to the servo tester circuit to achieve the same idea.
Can I get some more details about the "slotted drive" because I have been thinking that the servo tester has three functions 1. Manual, 2. Neutral and 3. Auto via a push button switch.

If I could take that switch out to the panel then I might be able to have manual control, the down side would be having to pass through the Auto function.

To bypass that I would have to find where that function comes from and disable/disconnect it. There is a micro-controller on the board so maybe there is a dedicated pin for the auto function.

Time to fire up the CRO maybe?

Now that is food for thoughts that will keep me awake.
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Re: Servo Controlled Points

Post by gregh » Mon Mar 08, 2021 10:14 pm

I finally found my post from 3 yrs ago.... here's the link. Watch my video linked in it.
https://gardenrails.org/viewtopic.php?f ... ol#p136033

Even 3 years ago I was thinking of using Dave Bodnar's tester too - and I'd completely forgotten it.
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Re: Servo Controlled Points

Post by gregh » Tue Mar 09, 2021 8:57 am

I've had a few more thoughts from my post above.
If you set the pot on the board to mid position, it can be the neutral position where the servo sits unless it is moving the points.
Then the additional resistor and switch connected to 0V shown by Bodnar, would become the position where the points move to in one direction. Then add another resistor and switch connected from the wiper but to +5V. When that switch is closed, it will move the points in the opposite direction.

I haven't tried it but it should be simple for you to try. I'd try 4.7k resistors to start.

In practice the resistors would probably need to be pre-set pots so you can adjust how far the point blades are moved.
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Re: Servo Controlled Points

Post by GAP » Tue Mar 09, 2021 8:03 pm

gregh wrote: Tue Mar 09, 2021 8:57 am I've had a few more thoughts from my post above.
If you set the pot on the board to mid position, it can be the neutral position where the servo sits unless it is moving the points.
Then the additional resistor and switch connected to 0V shown by Bodnar, would become the position where the points move to in one direction. Then add another resistor and switch connected from the wiper but to +5V. When that switch is closed, it will move the points in the opposite direction.

I haven't tried it but it should be simple for you to try. I'd try 4.7k resistors to start.

In practice the resistors would probably need to be pre-set pots so you can adjust how far the point blades are moved.
I already tried that setup but the servo didn't move when switched to the 5V. The pot is used to set one extreme of the servo and when the resistor is switched in moves it to the other extreme depending on the resistor value.

My main issue with manual movement is that 5 out of the 8 sets of points I have do not have over centre springs, I could make them using a safety pin the same as I saw on the S&T.
The main reason I am doing this is because my manual LGB points do not move when I throw the lever, so I have to tap the blades to get them to move into place. I have tried all sorts of lubricants from light oil thru to graphite to free them up but had no luck.

I have even toyed with using throws like Rik did but they make and break a microswitch instead of having a main panel, I would just have to go to the point to throw it the same as I do now and that is still an option but if I did that I may as well just use straight rods.
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Re: Servo Controlled Points

Post by gregh » Wed Mar 10, 2021 5:02 am

GAP wrote: Tue Mar 09, 2021 8:03 pm I already tried that setup but the servo didn't move when switched to the 5V. The pot is used to set one extreme of the servo and when the resistor is switched in moves it to the other extreme depending on the resistor value.
Rats! Thought that would work. I still don't understand why not.
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Re: Servo Controlled Points

Post by GAP » Wed Mar 10, 2021 6:23 am

I did find another funny; the small servos (HTX 900) I have move in the opposite direction to the large ones (HK15288A) I have, when connected to the tester.
No idea what is happening there.
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Re: Servo Controlled Points

Post by GAP » Fri Mar 12, 2021 6:39 am

This is a photo of my test rig with a mock up of how I plan to fit the servos, I have had good a suggestion about reinforcing the throw bar with a piece of brass or styrene to add strength.

I have gone with waterproof servos so I can mount them through the roadbed.

The micro servo on the right is for a signal, as it moves at the same time as the points servo I can add a semaphore to show which way the blades are set, I could even use it to open/close a micro switch to turn on and off a signal light. It would most likely go under the roadbed in a weatherproof enclosure.
Points servo fitting trial mock up.JPG
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Re: Servo Controlled Points

Post by philipy » Fri Mar 12, 2021 7:24 am

GAP wrote: Fri Mar 12, 2021 6:39 am ...as it moves at the same time as the points servo I can add a semaphore to show which way the blades are set, I could even use it to open/close a micro switch to turn on and off a signal light. It would most likely go under the roadbed in a weatherproof enclosure.
That is essentially what I did with my bracket signal indicating which way my three way junction is set.
Philip

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