Over a year without posting anything! Disgraceful - dunce's cap firmly on.
Despite the pandemic, lock-downs and other distractions, things haven't developed very much recently. The first lock-down was taken up with long summer walks and home-based IT work for a local charity. By mid-summer it was much too hot to work for long in the loft - 30degC plus some days. Then suddenly it was cold again!
Work restarted before Christmas (2020!) looking at the design of servo point motors. Having previously successfully used solenoid motors, they didn't look or sound very realistic. Small servos are (were?) inexpensive so how to make a compact but adaptable assembly to put under the layout? It needed to be cheap, easy to make with limited tools and easily repeatable - thirteen are required. Various scribblings and mock-ups were tried, eventually producing this not-very-original design.
The servo is a tight fit into the aluminum U-channel, and butts up against a short piece of balsa or similar softwood, on which the frog polarity micro-switch is mounted. My baseboard is just 3mm thick ply, so the pivot is mounted a few mm away in order to provide enough throw at the point blades. The bracket can also be mounted on its side if needed. There are screw mounting holes in the U-channel, but I found that double-sided black sticky pads normally used for affixing car number plates worked really well. A thin coat of PVA or paint on bare wood assists the grab of the pad.
The material used in this U-channel is tough and quite difficult to cut, so I also made a bracket using PVC U-channel. It isn't quite as rigid, but seems firm enough to resist side-movement from the servo. Here is one such:
The wire pivot bracket (out of focus at the back) still needs to be placed and glued onto this version.
These servos will be controlled by an Arduino and two LED/servo driver boards connected via an I2C bus. This has the advantage of few wires as mentioned in an earlier post - two data wires and two power wires in a screened cable. So happy times were spent during Christmas restrictions programming an Arduino Nano to move the servo by about 90 degrees - enough to move the point blades and reliably operate the micro-switch. The prototype mock-up works, so things a re looking hopeful.
Wiring track has also been proceeding as a background task, one board at a time. The corner board is now being worked on, with only a few droppers to fit. This is what it looks like so far:
So once the track power feeds are all soldered in, it will be time to re-assemble everything and do some test running - I can't wait!
The next few stages will include:
make more servo brackets
fit servos to baseboards
fit the control electronics
complete I2C wiring.
Watch this space!