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Turnout Operating Units

Heavy Duty TOU

The original version of my TOU connected by wire to the leverframe. The mounting of the microswitch is not characteristic here due to available space.

A more modern version under test using a relay. This one is for a double slip showing 4 individually adjustable strips of pcb each with a .8 mm tube. The end of the tubes are visible here. The relays have been replaced by a Tortoise motor being stronger and more reliable.

A more recent version of my TOU connected to a Tortoise.

Shows how to fix Tortoises when the depth of baseboard is less than the height of the Tortoise. The body is polystyrene thus some strips of white ps hold excellent giving additional options for screwing them in canted position.

A direct drive TOU mechanism using a servo with microswitch (or a stack of them) either 3D printed on the filament printer or milled version. The latter are quicker to produce thus have preference. The trick here is that the servo runs from full left to full right position driving the mechanism over an eccenter. The stroke of the ecccenter being adjusted with the central screw between zero to max ~3 mm. Thus there is only mechanical positioning with adjusting the stroke on installing but not any electronic. The servo simply runs over its full swing. However these cheap SG90 servos are actually a disaster as they are capable of doing full turns when the minimum pulse time is set too short. They don't seem to have any mechanical end stop. They function for the time being but beware and choose better ones.

This (unsharp) photo shows the full plastic version driven by servo on the extension of Splitveld. Here not only the prongs can be adjusted individually by an M1.4 in a long hole but also the switch has its own screw for in situ adjustment. Originally I intended to drive these TOU's over a mechanical connection from the lever frame thus these didn't have any inbuilt drive options but were left with overlong ends. However the space below the center board didn't allow for 5 sets of my mechanical solution of lever controlled rods with spring loaded torsion drive over the module ends thus these items were converted to servo drive. These seperate boards with a servo push (or pull in one case) the actual TOU mechanism. The spring in the microswitch enables the travel backwards. Thus in case of havoc I can remove the servo and operate by hand over friction after inserting a small wedge (e.g. insert a piece of wrapped up paper tape as wedge).

The control of the servos is by an Arduino UNO board linked to a PCA9685 board driving the servos. In order to drive this the leverframe was equiped with a series of microswitches that connect by cable over secure screwable GX plugs to the Arduino board. This PCA9685 board allows to drive 16 servos or other pwm controlled items. The servos have their own indepent 5V power supply as this turns out to be the only reliable way to control them from the Arduino board. Other microcontroller boards are equally well suited because connection is by I2C. Thus remote connection over wifi by ESP8266 is for instance an alternative option.

The Model Lever Version

This shows the top view of the lever in unpainted condition, with 2 rods connected to a tongue each. The rods are soldered to a tiny piece of pcb. One of these rods is connected to the lever. The pin is connected to a below baseboard microswitch.

Blown-up side view. This is a N-gauge / fiNe scale compatible point that is why the gaps are very large.The crossing gap is filled so that the fiNe-scale wheels don't drop in the overwide gap when in fiNe scale use.

Here you see the crossing. Only right hand side is N-gauge with a adjustable point gap by a movable check gauge.

copyright: Henk Oversloot
date: 15 mei 2003
updated: 12 Feb 2020