Point Control on XPS Foam


R

regme

Well-Known Member
Hi

I have kind of stalled in my layout build. I'm not sure how to control the points, my baseboard is 50mm XPS foam glued to 3mm ply.

I was going to control the points with servos and arduino, I have modelled a linear actuator, so I could mount the servo off to the side and hide the wire under a 3D print point motor.

I have tested this on a 12mm board and it seams to work fine when the piano wire goes through the hole in the point, it kind of works when it the wire goes under the track towards the point motor.

The issue I have is how to install the linear actuator to the baseboard, from the underside of the baseboard to the top of the sleepers varies from 60 to 90mm, which maybe way to much for the piano wire to handle without bending. I have thought about using a bass tube with piano wire placed inside and soldered or glued in place to make it more rigid.

I was wondering how others may have installed point motors when using XPS foam, unfortunately I have laid the cork roadbed, which adds to the woes. I'm a bit hesitant to cut a big hole in the foam to place the whole point motor, but open to ideas.

Yes I have over engineered this.

Cheers

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How about cutting a piece of foam/wood from under the switch and mounting it on a solid fixed piece?
 
I can do that on certain turnouts, but I have one on an embankment and the hole would ruin the batter.
 
Hi I make small frame using 1/4" plywood. I put a 5V servo into the frame, and attach it to the underside of the layout. I use 1/4" plywood with 2 inches of foamboard for the layout base. I glue the assembly to the foam with caulk, then add a couple screws for mechanical support. I run a small brass tube from the underside to a point 3 or 4 ties from the slider where the points are attached. The tube is cut to extend from the top of the ties to the height of the actuator arm on the servo. Then, I make a small hole in the middle of the slider. I then bend a thin steel "piano" wire into a hook which fits into the slider hole, and bend it to drop into the brass tube. At the bottom of the tube, I bend the wire to fit into the arm of the servo. I put a "kink" in the wire- not a straight run from the tube to the actuator arm to absorb slight bending during actuation. I use an Arduino for control and to control position LED indicators.
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Hi

I going to have to think this through.

I wouldn't picking your brains on the Arduino side of things also.

Cheers
 
regme said:
Hi

I going to have to think this through.

I wouldn't picking your brains on the Arduino side of things also.

Cheers
Click to expand...
Hi I will try to post more pics. I put them somewhere in the computer, so of course, I cannot find them... I made a bunch of these at one time- mass production (heehee). But, the design is flexible- I can position it wherever, caulk in place, then add a couple screws (belt and braces thing...). Rock solid performance.
The Arduino- just need one Arduino UNO for every three switches (I drive indicator lights on the control panel, the switch relay boards (5V separate supply- NOT the Arduino 5V, not enough juice.), and a separate drive relay for the block indicators. I have the code that I wrote if you need it. Let me know. I can add comments in the code to make it more understandable. I have also used Arduino MEGAs to drive up to 8 switches, with relays, indicators, block lights, etc. It handles 50-some I/Os. See below.
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Hi
Thanks, I have been messing with a sketch I found on-line, just to get an understanding of the whole thing.

The aim is to use an UNO with a PCA9685 with a DPDT switch to throw the points and drive the LED's on the control. However finding the code for a DPDT switch is proving a bit harder to find.

The sketch I found only uses a push button, but I have one point working (well testing before I hit the layout. Still ironing out the bugs.

Cheers
 
Hello regme
The UNO or MEGA can drive a servo directly- it uses the +5V source pin, and two active pins to ground (driven in the code). The LEDs can be driven from two other active pins to ground, and the +5V with a 1.5 or 2.2kOhm series resistor on either of the LED leads. You use the push button to activate the change-of-state within the code. The UNO or MEGA is constantly watching the I/Os for any change of state, then acts on the change when you push a button. The LEDs are changed with the position of the points. I use red and green LEDs on the control panel to show the point position. The servo does not pull significant current in operation or in hold (unless there is a strong "pushback" in the linkage- which is not desirable.)
I have a bunch of the PCAs that I bought, thinking I would need them, but did not use them. The UNOs and MEGAs are more robust than I thought. I did pick up a bunch of 5V-5Amp switching power supplies for less than $5 bucks each... So, I have about 75W under the table for 5V ( and a couple of spares), and then I put in 1 and 2 Amp boost converters to get +9V for lighting effect circuits, and +10V for all of the UNOs and MEGAs, These converters were like 75 cents or something like that (ridiculously cheap). Beats buying a bunch of wall-worts!
I use a +19V DC supply that I built for powering all of the coil-type switch machines- designed it to be a capacitive-discharge type of unit- large capacitors are cheap! I drive these from push button inputs to either an UNO or a MEGA, which drive relay boards (quad or octo), powered through the 5V supplies, with the switching logic fed from the microprocessors. Sounds more complicated than it is...
I have about 10 different sketches that control switches and relays. Let me know if you are interested.
 
Hi

Thanks, definitely interested, as I'm relatively new to this Arduino thing you will have to bear with me. My layout has only 12 points, that's why I thought the PCA9685 would be the go.

Do any of your sketches use a "on-on" DTPT switch? I was hoping to recycle the ones I have from a previous layout I had.

In the previous layout I had the peco switch motors, so the DTDP switch would control the point thrown while the other side did the LED's on the control panel. I was hoping to use the same philosophy.

Cheers
 
Hi To cover 12 switches with indicator LEDs, etc., you could use 2 UNOs and 1 MEGA. An UNO only has enough pins to handle 2 switches. The MEGA can handle 8 pushbuttons, 8 switches (two relays per switch) and 16 LEDs without issues- lots of wires! You might have a few extra I/O in the MEGA. I think I understand your use of the DPDT switch. The way I programmed the whole thing, effectively I make two relays act as a DPDT, but with additional drivers for the LEDs, and the system is fail-safe in that if power fails, everything stays in place. Also, with the internally-set timing, power cannot be applied to the switch coils for more than XX milliseconds (settable in the program). I use about 100 to 150mS, some switches are stickier than others... Again, power fails, no actions.
The good thing is that Arduinos and related parts are cheap on the internet.
PS- right now we are out of state, not due back until mid-Sept, so until then, I cannot send you any files.
 
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