Tuesday, May 29, 2012

2 solution to move points with a servo

I’ve experiment Tam Valley Octopus servo Driver from his first version. This have software that just leave the user to select between some “angle” of movement” of the servo arm. I have to install  hand laid turnouts that need a strong force to maintain the points in pressure, and I want a solution that can be installed from the top of the layout, after the turnouts are already in place…
With this limitation in mind I select a solution that use the flexibility of the music wire to provide the necessary strength. 
See on this post what I’ve done at the time:

Then Duncan ( Tam Valley owner) add the Auto-Align software ( this will find automatically the end-point where the point rail are pushing the side rails)…. I’ve try also this cards, but find the trick some difficult, at least with my turnouts in N scale.
Now a new software is loaded in the last Octopus III version, where a “manual adjustment” is allowed (along with a more comfortable handy keypad! ) and this …. It’s exactly what I’m waiting!
The “auto” followed by a “manual” programming have solved all problems and ( also because a friend have critiqued, and I agree, the visual aspect of the previous mechanical solution ) I was ready to find a more “traditional” way to install the servo.
A visit to the bricolage shop and I take home the proper tool: one aluminum bar of the same dimensions of the servo!

Here you can see a video with the two solutions: https://vimeo.com/43026665

-          Aluminum “U” bar cm1,5 x 1 cm (more or less 4$ for a meter ) : |___|
(I figured it was better to have metal at the pivot point )
-          SG90 Servo with moving arm accessory
( I’ve buy a quantity from : http://stores.ebay.com/top-racing2007 ( use the search field and type SG 90 for some bulk pack at good price: $2,5-3  for >12 pcs.)
 Tam Valley also sell for SRV002   $4.95 USD)
-          Music Wire .032" (available from Tam Valley, but also from LSH or WallMart)
-          Strong foam double face tape
-          Tam Valley “Octopus III” 8xservo driver card: OCT030   $32.00 USD
-          Tam Valley Remote Aligner for Octopus III: OCT031   $12.00 USD
Note that Tam Valley have discount prices for quantity.
Fascia Controller for use with Quad/Octopus II/Octopus III:  FCB010   $2.50 USD
Remote DPDT Relay with Y Cable: DY5001   $7.00 USD

(above pictures from the Tam Valley web site)

The second solution: “a la Tortoise”:
1)      Cut a piece of 4 cm. from the Aluminum “U” bar

2) Place the servo as show inside the bar without the tape
 3) Place the moving servo arm without the screw and using the music wire put a point on the aluminum bar leaving the music wire in vertical. “Dremel”  a 1mm-1,2mm hole

4) If you’ve already installed the turnout on layout, or the turnout is in a place too difficult to work from bottom , then position the turnout with point opposite to throw bar end where you want the wire and sign the place for the wire hole just in line with the throw bar end. Drill a 3-4 mm hole from top of the plywood.
5) Now using the double tape fit the servo inside the metal bar
6) Bend the music wire to the servo arm as show.
7) Connect to Octopus and position the Center Jumper on CENTER (servo will move the arm in the middle position) . Screw the servo arm to be on line with the 1mm hole.

8) Fit a piece of tape on top of the metal support and From “downunder” ( but without touch the plywood) insert the servo more or less in position. Try to emulate the arm movement to find the best servo position. Push the servo in place.
9) With the arm always in CENTER move also turnouts point to center. As I’ve a copper plate throw bar, I’ve used one thread of electric wire turned on the music wire to make the connection to turnout throw bar and solder to it (use always some flux)
 10) Program the Octopus III and enjoy !

1 comment:

Coxy's N Scale and Railroad Blog said...

Nice job Enzo. I like the idea to use the aluminium channel to make the mounting bracket.
Steven Cox