I don’t have much knowledge of signalling, and had no signals on my layout, but a friend mentioned it would be nice to operate semaphore signals with a servo motor and ADD THE BOUNCE FUNCTION. (I’m assuming Lower quadrant types.) So I took it as a challenge.
I found this video on youtube illustrating the movement and bounce from clear to stop…
https://www.youtube.com/watch?feature=player_detailpage&v=V31E8pmml3Q#t=40
From the video I examined every frame and determined the following timing for the bouncing from clear to Stop:
Initially ‘clear’ at 50deg down.
Takes 0.56 sec to rise to horizontal
Then bounces down 18 degrees in 0.40 sec (0.98sec)
Stays there for 0.08sec, then (1.06s)
Rises to horizontal in 0.48sec (1.52s)
Bounces back down 6 degrees in 0.18s (1.76)
Waits 0.08s, (1.84s)
then bounces back up to horizontal in 0.32sec (2.16s) and stops.
From this I deduced that the movement from clear to stop operates as if the arm is ‘falling’ due to gravity – ie a constant force is applied. This means the arm starts off slow and accelerates.
From other videos, I deduced that when going from stop to clear, the arm seems to move with a constant speed.
So I set out to write a Picaxe (08M2) program to give constant force going to stop, with 2 bounces, and constant speed going to clear, with one bounce. The program provides the servo pulses to operate three signals.
I made three signals from styrene, with a micro servos to provide the movement. (only two are servo operated at present – the 3rd is operated by a piece of fishing line attached to the turnout!)
A micro servo provides the movement. The Picaxe and associated power supply is in a small plastic container and the whole box is inside a ‘signal hut’, as shown here:
My signals are mainly to let me see the position of turnouts from a distance, but can be thought of as ‘starters’. So they are not true prototype, but good enough for me.
The Picaxe program has two inputs from the two turnout positions (reed switches and magnets) and can operate the three servos. (signal ‘F’ is still operated by fishing line)
So here’s a video showing the operation of the signals ( including my small railcar with Picaxe RC and sound – but that’s another Picaxe story!)
