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  • Topic: Servo controlled turnouts/points

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    • March 19, 2021 8:19 PM EDT
      • Candlewood Valley, Connecticut
         
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      My 4 Channel relay module arrived today. For $7 it didn't make sense to solder up a bunch of relays.  This board has 4 SPDT 12V relays that can be triggered via optocoupler with either a high or low logic signal.

       

      RailPro lamp outputs are a switched ground, therefore function as a logic low signal. I daisy chain the input of two channels for one turnout. One channel triggers the servo movement, replacing the SPST switch in the Bodnar circuit. The other channel will be for position feedback to RailPro [If I am successful at using their turnout program] and also supplies power to the position indicator LED. For simplicity, and since I have them in-stock, I am using common Anode RGB LEDs for the position indication.

       

      In the photo, the relay module is at the top, above the servo with an LED connected directly to the module.  Not shown is a RailPro LM-3S-G which is temporarily being used to trigger the relay. The RailProc HC-2-SUN is at left. The second to last button on the bottom row controls the turnout. One photo for each position, Straight with Green LED indication and Curve with Red LED indication...

       

      I've also done some fail-safe testing.  The default power-on position of the Servo Tester is for the straight route.  If I throw the turnout to the curve position, then power down the system, it will stay put so long as power is gone, but returns to the default straight route on power-up.

       

      The last piece of the puzzle is the RailPro AM-1 accessory module, which I hope will be here soon.

       

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    • March 21, 2021 6:12 PM EDT
      • Candlewood Valley, Connecticut
         
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      As an exercise to learn a bit more about my upgraded version of Visio (I skipped 22 years of updates), I tried my hand at drawing what is working so far...

       

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    • March 21, 2021 10:14 PM EDT
      • Bundaberg, Queensland Australia
         
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      Jon Radder said:

      As an exercise to learn a bit more about my upgraded version of Visio (I skipped 22 years of updates), I tried my hand at drawing what is working so far...

       

       

      Looks good.

      Could you used a DPST relay instead of a 2 x SPST relays with 1 pole switching the trimpot and the other switching the LED?

      Only using 1 relay board input for 2 devices.

    • March 21, 2021 11:20 PM EDT
      • Candlewood Valley, Connecticut
         
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      GAP said:
      Looks good.

      Could you used a DPST relay instead of a 2 x SPST relays with 1 pole switching the trimpot and the other switching the LED?

      Only using 1 relay board input for 2 devices.

       

      Yes, I absolutely could.  I am only doing 2 turnouts in close proximity. Relay boards with 4 SPDT relays were dirt cheap, 2 DPDT relay boards were three times the price!  So, it was a financial decision!

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    • March 23, 2021 5:05 PM EDT
      • Bundaberg, Queensland Australia
         
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      Jon Radder said:
      GAP said:
      Looks good.

      Could you used a DPST relay instead of a 2 x SPST relays with 1 pole switching the trimpot and the other switching the LED?

      Only using 1 relay board input for 2 devices.

       

      Yes, I absolutely could.  I am only doing 2 turnouts in close proximity. Relay boards with 4 SPDT relays were dirt cheap, 2 DPDT relay boards were three times the price!  So, it was a financial decision!

      Ah  a man after my own heart when it comes to spending money I am very thrifty (wife calls me cheapskate)

    • April 10, 2021 6:17 PM EDT
      • Bundaberg, Queensland Australia
         
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      I installed one servo tester, wired it up to the 5V the bus and mounted a switch to the control panel.
      Next I installed a servo next to a point and connected it to the tester.
      Following that I connected the servo horn to the point throwbar via a control rod with a clevis pin at one end, on the other end of the control rod at the horn I put a "Linkage Stopper" (these are used by the model aircraft people quite extensively).
      The stopper has a grub screw adjustment so when I set the servo travel extremities using the 2 pots I could make fine adjustments to relieve any residual tension being applied to the control rod.
      As the point I started with was on a crossover, I attached another servo to the other point and connected it to one of the tester outputs (there are 3) and now both points change at the same time controlled from the one control panel switch.
      Now that I have it all working I will proceed with installing the rest of the servos to my points (12 of them).

      The servos I am using are waterproof and are mounted under the baseboard.
      I ran my irrigation sprays that are under the baseboard and no sign of any part being wet.
      We also had 4 days of heavy rain and no water got under the baseboard everything was dry.
      I am going to put a smear of silicone grease around the servo shaft to increase water repellence around its entry point.

      I am using double walled heatshrink with a glue inside to keep moisture out of wiring joints.

      Picture of the control rod showing the clevis pin and the linkage stopper.

      Merged_document (1).jpg

    • April 11, 2021 8:53 AM EDT
      • Candlewood Valley, Connecticut
         
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      Looking good!  My project has stalled in the breadboard stage.  Weather got better and my attention turned to finishing repairs on my RV so we can go camping soon.  I did order a RailPro AM-1 accessory module from Don Sweet that will be here early next month.  I'll keep the breadboard setup while I work out the interface.

       

      I do like your linkage ideas. Much better that trying the bend brass to exactly the right length! I bought a bunch of clevises and other push rod parts when my local Hobbytown closed up, so I should have everything in-stock to follow your lead.

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    • April 14, 2021 4:55 PM EDT
      • Bundaberg, Queensland Australia
         
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      I have published a page on my blog which shows the whole install of the servo controlled points, it contains links to the original article and the components used.

      https://ringbalin-light-railway.blogspot.com/p/servo-controlled-points.html

       

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    • April 15, 2021 9:05 PM EDT
      • Candlewood Valley, Connecticut
         
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      GAP - In your blog post you mention that some of the testers worked differently. Did they all come in the same order from the same source?

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    • April 16, 2021 1:22 AM EDT
      • Bundaberg, Queensland Australia
         
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      Jon Radder said:

      GAP - In your blog post you mention that some of the testers worked differently. Did they all come in the same order from the same source?

      Yes they did;  the only way to physically tell the difference was by the colour of the circuit board, the other way was at power up with a servo connected it moved the servo to the travel extremities before settling at the point where the control knob set the position.

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    • April 21, 2021 4:20 AM EDT
      • Bundaberg, Queensland Australia
         
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      Just to add to my last post;

      By using the linkage stoppers and loose connection of the clevis pins the full extremity travel can be overcome, the servo just moves to the limits and then settles at the default point because the linkage allows it to travel over centre without applying excess pressure on the throwbar.

      Hope that makes sense.

    • April 21, 2021 5:26 PM EDT
      • Candlewood Valley, Connecticut
         
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      GAP said:

      Hope that makes sense.

      It does, but that sounds like you would need to do that every time the system is powered up. I know you are using a solar charged battery, but there is always a chance that battery will go flat.  In my case, I'm using a power supply powered by house voltage and our power drops out fairly often. That's why part of my design criteria was for the points to return to main-line route on power-up, even if the diverging route was selected when the power dropped out.

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    • April 22, 2021 2:02 AM EDT
      • Bundaberg, Queensland Australia
         
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      Jon Radder said:
      GAP said:

      Hope that makes sense.

      It does, but that sounds like you would need to do that every time the system is powered up. I know you are using a solar charged battery, but there is always a chance that battery will go flat.  In my case, I'm using a power supply powered by house voltage and our power drops out fairly often. That's why part of my design criteria was for the points to return to main-line route on power-up, even if the diverging route was selected when the power dropped out.

      Jon,

      The tester goes through a self test at power up as part of its programming (I can't change that), if it is powered only once then there is no self test ever again.

      While it is performing the self test the linkage stoppers and the sideways travel of the clevis in the throwbar slot allow it to go through the motion without damaging the throwbar or the control rod.

      If power is removed then once it is re applied the tester would go through the self test regime, the stoppers etc allow this to happen safely.

      I am not using that type of tester on my layout so it is not an issue for me at this point in time.

      I am just pointing out that it may happen depending on what is delivered and I may have to face the issue if I increase the number of testers in the future and end up with the self test version.

      My default is also for mainline route.

      This post was edited by GAP at April 22, 2021 7:16 PM EDT
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