Proposed design of inexpensive signal driver.
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| Schematic diagram of signal driver for small layout |
Why ? Costly in cash and time, signal TTL logic circuits and detector wiring etc etc
was a major factor in choosing my design. Designing full circuits for MY layout would
have taken months. This design is a compromise. Modelling is about "Suspending Dis-belief."
And same with signalling, if my layout has twenty four twinkling signal lights and I am ask to
stop at a red which then changes to double yellow – all is good.
What ? The materials list should be obtainable from a local electrical/hobby shop.
Terminal blocks to join wires to LED lamps and contacts. Cog gears to turn the drum
(a metal can of sweet corn). Uses layout 12V DC power supply. POF - polymer optic fiber,
an inexpensive light transmission to the scale signal head. $1.00 high luminosity LED diodes
are becoming more available. A inexpensive 3V motor with gear reduction is available
from Tamiya
http://www.1999.co.jp/eng/10099038
How ? The main feature of the design, is the drum. The drum pattern revolves under
the row of contacts. Sticky cloth tape will give open circuit and bare metal section
will close the circuit. This action generates a sequence of signals. One revolution
should be approx. 30 seconds. (scale time = 5 min). The drum box will have six
terminal blocks connected to a row of contacts (see 8 tag strip in image below). A
4-aspect and 3-aspect signal each row. This can be double to provide 24 signals by
wiring two runs to each terminal hole. Arranging the location of each signal so that
the sequence is followed will provide some realism. A 60 tooth gear will be fixed to
the drum and 12 tooth gear will be driven by the low speed motor at a final two rpm.
Note that the 3aspect signal pattern on the drum does not need to have the same
start point as the 4aspect. I have only drawn it that way for clarity. Regarding the wiring
of the LEDs, you will need to insert resistor for each LED depending on its volt drop.
My diagram uses a common resistor for all but not practical.
Downsides ? The gears may be noisey. (foam box cover may help) The sticky tape
may wear off. Contacts to and from drum may get dirty.
Credit for POF idea :-
http://nscaleaddiction.blogspot.com.au/2012/01/cheap-simple-n-scale-signals-using.html
Future mini-project will be a digital option based on this mechanical design. More 1980s than 1880s.
Using cyclic 7555 CMOS timer chips...
