Servo Driver Kit

The servo motor kit as constructed and ready to use.
A servo mounted for use switching a point or turnout. This view is from underneath the layout and upside down!

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Code Description Price A$
SD020 Servo Motor Driver Kit - "Temporarily Out Of Stock $6.00
SD021 Connector for Servo Driver $0.50

The servo motor driver kit enables a standard model aeroplane servo motor to be used for precisely controlling the movement of signals and turnouts. It is self locking and is of particular advantage for fragile signals and pointwork.

Instructions for constructing the kit, wiring diagrams and servo mounting photos for points/turnouts are available for download as Acrobat (pdf) files. You will need an Acrobat reader to open them - if you do not have one please click here.

  • 1. Instructions for Servo Driver construction - pdf file (81kB) - download.

  • 2. Wiring diagrams - pdf file (208kB) - download.

  • 3. Servo mounting photos - pdf (149kB) - download.

Supplementary Instructions and Notes

Noise can be introduced into the servo driver by the power supply, bad earthing (don't connect the earth of the servo power supply to any other earth on your layout), long wires from the board to the switch, the switch itself, badly made or cheap servos, etc. Noise can even be introduced by touching the wires to the switch (it will possibly vibrate and move to some extent).

If you are having stability issues (ie: the servo vibrates and moves erratically) you can try shortening or re-routing the wires (particularly to the switch if possible); changing the servo to a different brand; using shielded cable on the switch wires; use a separate power supply (if you are not doing so already); or use a pair of SPST throw momentary on switches to move the point to the left and right. The latter is an effective solution and has some advantages. What these will do is when pressed is move the servo to one of the set positions and then disconnect the power. This has some advantages as no power will be used when the servo is in either position (which is most of the time). Note that for model railway purposes the servo is effectively locked when no power is applied to it. Clearly in this scenario noise will not be able to interfere with the servo once it is set in either position. To set the servo extremes you will need to keep each one of the switches depressed in turn while adjusting the pots.

SPST momentary on switches are available from Jaycar (SP-0710 Red or SP-0711 Black at $1.45 each for 10+ quantities).