Post 9 from my old blog (from ~2011)
This now happened quite a while ago now but as luck would have it, barely a week after I made my last post on using muscle wire for turnout actuators my last bit of wire broke :-( It was a bit of a shame really, as the test rig had operated for months without any problems.
What happened was that I built an actuator based on the crank system as described in a previous post on servos and at Tamalpais Valley Railroad, but instead of using a servo to move the crank I reused my last bit of muscle wire to pull on one side of the crank and a spring on the other side to pull the crank back. I used a small piece of styrene with 3 holes in it to connect the muscle wire, the crank and the spring:
This setup worked well for about 6 weeks. As with the initial test, I actuated the wire by flipping the load switch on my power supply half a dozen times each morning and then left the switch on for the rest of the day, so that the muscle wire was under load most of the time. The turnout worked flawlessly until one morning I noticed there was no current flowing through the wire (my power supply has a current meter). Turning over my test rig I saw that the muscle wire was broken. (Read more)
Post 8 from my old blog (from ~2011)
Well I know I haven’t posted much in a while, but rest assured there have been exciting developments going on over here on a number of fronts.
The first thing is, I am gradually becoming convinced that I may have ‘cracked’ the holy grail of finding a cheap turnout actuator for my layout. My last couple of posts have looked at using servos, and they show a lot of promise, however I have been experimenting with something better - muscle wire.
Now, truth to tell, I have thought of using muscle wire - Nitinol wire - for a long while now. I bought a wire sample kit and book nearly 10 years ago and have off and on (mainly off) tried to actuate turnouts using various mechanisms. I have a small drawer of ‘experiments’ gone wrong as you can see here: (Read more)
Post 7 from my old blog (from ~2011)
I’ve been working on low cost ways to control turnouts. I bought some servos (AU$7 for 4) on eBay and tried to operate my hand made turnout with one of them. Here is a picture of the initial setup:
Servos need about 5 volts plus a pulsed control signal to work. I’ll eventually use a microprocessor to generate the pulse, but for now I’m using 555 timers. The circuit on the breadboard contains two 555 timers. The first timer generates a continuous pulse 50 times per second. This pulse triggers the second timer which then produces a pulse between 1 and 2 ms, depending on the knob. (Read more)