One of the biggest issues I've had with previous model railroads is getting switches / points / turnouts (whatever you call them!!) to move electrically.
The normal switch machines sold by Peco are pretty hefty and draw a fair bit of current - up to 2A. This means that you need a Capacitor Discharge Unit and some heavier electronics to make switch motion happen under computer control.
Also, these solenoid point motors are really 'snappy' in their action. Partly this is driven by the fact that the Peco points have a spring in them which holds the blades against the track in either position to ensure electrical contact and to ensure derailment does not happen. This means you need a hefty point motor to overcome the spring. Also, the motion of the point looks crappy, not like a real railroad at all.
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| The circle shows the spring in the Peco point. It has to go! |
So, you have to remove the spring. I'll show you how I did this in my next blog post.
The video below shows the snappy movement of the switch.
I'm working on a nice test layout that I made to allow for experiment. A photo appears below.
I've made this from 6mm foam core and it is mounted on 50mm wide strips of foam core that run the length of the layout. I mount the tracks on 3mm foam core to allow for under track devices like sensors etc.
What we are looking for is nice smooth motion of the blades of the point like this...
Basically, the best way to achieve this without going to a tortoise machine is to use servos motors. I get my servos from DealExtreme.com along with some nice servo extension cables. I paid about $4.50 including postage!!
The movie below shows the same point from under the bench and you can see the servo moving - this time under manual control.
Now, you can see that at the extreme ends of travel, the servo can make quite a racket so you need to tune the positions of the servos. I do this using software and this allows me to mount the servo with a certain amount of error.
Note that once you remove the spring from the point, you need to use the servo mounted spring wire to hold the blades into the frog.
You can see my simple mount in the movie above. This movie shows the normal controlled motion of the servo.
Just for completeness, I've put a few photos below of the point with the spring removed and the servo mounted underneath.
So, get yourself some servos and an Arduino and start making it happen!
More on removing the spring and the actual electronics in a future blog post.
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