Automated Level Crossing Prototype

One of my background tasks for the last year or two has been building an Automated Level Crossing to go by the halt. There are various designs around, but many are very complicated and often too deep to fit under the baseboard.

This shows the gates on the current prototype – it operation, they all move so that they close either the tracks or the road:

Underneath, it’s a bit more complicated:
Each gate is mechanically connected to a servo using a pair of gear wheels. The servos have small motors that are driven by the electronics in the middle.

The end position of each gate can be independently set using the small push buttons on the electronics board. The speed of movement can also be programmed.

Originally, this used standard servo arms to connect the servos to the gates, but these didn’t move the gates to the exact position reliably.

I spent a while looking for better solutions, then looked at various designs of gear wheels on the internet, found something the right size and then printed them on the 3D printer:

They are a bit rough, but serve the purpose and seem to work well.

Now I’ve got the mechanics right, I need to find some better level crossing gates before adding it to the layout.

 

Mounting a point motor

To make the job of mounting the new points on the layout easier, I’m experimenting with a method of attaching the point motor directly to the point, allowing the whole assembly to just be dropped into a suitable hole on the layout.

The first stage is to glue some thin plastic to the point sleepers – I used a bit of case from an old 8″ floppy disk (left over from the very early days of computing…):The plastic is wider than the hole will be, so should cover any gaps. There is a small gap in the plastic to allow the control wire to move the tie bar.

On the underside, a 38mm x 50mm piece of 6mm plywood is glued to the plastic, and the point motor (Conrad) screwed to this (1.5mm hole). The screws are too long for the plywood, so the excess are trimmed:
Wires from the point frog and rails are soldered to small pins in the wood. This allows a switch inside the point motor to change the frog polarity:
Two more pins allow a connection to the point motor itself:You can just see a spring steel wire on the right, which connects the moving arm of the point motor to the tie bar on the point.

Finally, wires are attached to the pins; the red ones will go to the point motor driver, the other pair to the track power:

Update 1
I’ve used a different arrangement for the spring steel wire on subsequent points:

This uses a much thinner wire (the thin wire supplied with the motor), constrained by the short copper tube under the motor. This produces enough force to move the point, but no so much that the point could be damaged should a problem occur.

Update 2

More point motors have now been fitted, and this photo shows a neater method for the construction and wiring. This motor is fitted a 6mm plywood base on 1.5mm black plasticard, with the point glued to the other side. This should match the height of the 1/16″ cork overlay, providing a constant top surface on the layout itself. Note that the wires are taken around the opposite side of the motor to the actuator wire.

Note the thin red wires on the right that take the power to the point and frog.

Frog Juicer

The frog on the one point on the 009 (Narrow Gauge) track has never been very reliable electrically. I was going to replace the point, but it would have been a lot of work…

So after a bit of experimentation, I added a small electronic board (Frog Juicer) that automatically sets the frog part of the point to the correct state.

mfj003

It only needed one more wire adding to the layout (and unless you know where it is, you’ll never see it), and the point is now very reliable in operation.

 

New Mimic Panel

As the track layout has now changed, the existing mimic panel was out of date. It needed rebuilding anyway, so it was easier to start from scratch with a new panel. This panel also shows the state of all of the layout signals.

This uses a sandwich of 2 sheets of 3mm clear Acrylic sheet with the printed layout between them. The holes for the lights are just drilled in the rear sheet, with holes for them cut out in the paper.

1407-009 Model Railway - New Mimic Panel

The new panel fits into the same wooden frame on the windowsill that the old one used.

Train-Tech Signal Construction

There are many options available for colour light signals, however, many of the commercial solutions are let down by using LEDs that are either oversize or have unrealistic colours.

After investigating a number of solutions, I’ve found a simple method of fitting LEDs that look much more like real signals into a Train-Tech SK1 kit. The SK1 kits cost around £5, the LEDs and other bits around £1.

Train-Tech do sell kits with LEDs already fitted to a PCB, but the size and colours of these are poor. In addition, the PCB sticks a long way below the layout, making them difficult to use without modifications on all but the deepest base boards.

LEDs

After much research, I’ve found the OSRAM “TOPLED BLACK” range to be the best currently available at a sensible price. This is a surface mount LED, but the pads are large enough to solder wires directly to them. They are primarily designed to be stacked together for LED message boards.TTSIG - Image0The front dome is the right diameter for a 00 signal, and “True Green” LEDs are available, which are a much more realistic colour than standard (‘yellowish’) green LEDs.

Colour Part Number Wavelength Resistor
Red LRT64F-BADA-1 625nM 22K
Yellow LYT64F-BBDA-35-1 590nM 10K
True Green LTT64G-DAFA-29 528nM 150K

You will find similar part numbers listed; these generally refer to devices with different average light intensities.

The resistor values shown, when used with a 5V supply, give an appropriate light output for a layout, with a reasonably similar intensity for each of the different colours. The 150K resistor for the ‘True Green’ LED is not a misprint; these LEDs are VERY efficient. Use higher values for a 12V supply; lower values for a multiplexed drive.

RS Components stock these LEDs, though only sell them in multiples of 25.

Construction

Solder a couple of lengths of 0.5mm tinned copper wire together, and bend them as shown.

TTSIG - Image1

Fit the LEDs (in the correct order and polarity) into the back of the signal. A bit of glue can help to stop them flying away. A 5V power supply with a 4K7 resistor in series helps to identify the colour and polarity of each LED. Solder one arm of the wire to the negative LED pads, taking care that the ‘Y’ of the wire is in the right place for the back to fit,. Make sure it does not touch the other pad of the red LED:

TTSIG - Image2

Now solder some very thin insulated wire to each of the positive pads:

TTSIG - Image3

Ensure the signal head base can slide over the wires, and check that the signal head back still fits. Don’t glue anything at this stage, but test it works electrically. Slide a piece of heatshrink sleeving over the tinned copper wire so that the post doesn’t become ‘live’, then slide the post up to the signal head:

TTSIG - Image4

The base can then be fitted. Put a kink in the thick wire to stop the signal coming apart, and solder wires to the various connections; I stagger the connections so they won’t short:

TTSIG - Image5

Cover the connections with another piece of heatshrink sleeving, and glue the signal head back and front together.

TTSIG - Image6

The signal is now ready for fitting to the layout. The ladders and other parts are best fitted after the main signal is installed. The connections and wire underneath can be gently bent to suit.

TTSIG - Image7

Whilst this example shows a three aspect signal, the process is the same for two or four aspect signals.

Ready Made Signals

To change the LEDs on ready made Train-Tech signals, first carefully remove the existing LEDs from the PCB:

Clean the old solder from the pads, but put a fresh blob of solder on the three top (common) pads. Then tack the new LEDs onto the common pads, checking that:

  • They’re flat on the PCB.
  • They’re the right way round.
  • They’re the right colour.
  • That the cover still fits.

When you’re sure everything is OK, solder the remaining legs to the pads.

I also used this method to replace the LEDs on a SK7 Dual Head signal kit.

TTSIG - Image8

Even More Layout Lighting

I finally got a chance to get some more wood and have constructed the last of the layout lights.These have all been made using “5050 Day White” LED strips stuck on to “Scotia Mouldings”…

Applying LED Strip

LED strip on wood

A wire is soldered onto the strip, normally somewhere in the middle. This goes through the a hole in the strip and into the wall:

LED Wiring

Once attached to the wall, the wire is invisible:

Layout Lighting - Country End

Note that it’s the wall that’s wobbly, not the lighting strips!

All the layout lights together take 42W of power – it’s a LOT of light for not much electricity. The next project will be a dimmer to turn them up and down as required.

Revised Power Supply

The railway power supply arrangements have been revised. As more electrical bits were added to the railway, the original solution was running out of ‘steam’.

Revised Power Supply

The gold coloured box at the top is the main power supply for the layout. This will deliver up to 10A at 16v.

The silver unit on the left steps up the 16V to 24V to supply the point drivers; this has improved the point reliability now that the track has been ballasted.