Simple Signal Controller for Model Railways         Code: RK-SSS and RK-SSSP

For the junior modeller, or the modeller who wants a result with the minimum of fuss, the Simple Signal Set (SSS) uses a light sensing detector in conjunction with a time delay circuit, driving a two colour signal. When a train passes, it cuts off light to the detector, which causes the signal to go from green to red, for approximately either 12 or 25 seconds, after which the signal turns back to green.

The emphasis is on a simple implementation - modellers who want something more sophisticated should consider the module SBP4, details of which are available on this web site.

A fully constructed unit is shown at right. The terminal block nearest the viewer has connections for the signal LEDs, and for the 12 volt input. The LED outputs will drive common cathode Light Emitting Diode (LED) displays directly. Many commercially available Signal Masts will accept 3mm LEDs, or a modeller may elect to construct his/her own.

At the opposite end of the Printed Circuit Board (PCB) is the light dependent resistor which acts as the detecting element. This is designed to be inserted in a hole between the rails, and bent so that it ends up level with the tops of the sleepers.

This is a very simple system to install, yet gives a changing signal aspect in conjunction with a train passing. Its operation may be summed up as
            "Train passes - RED. Time passes - GREEN."

The unit requires approximately 35mA from a 12 volt supply.

A slightly more advanced unit is the kit RK-SSSP. The basic concept is the same, but this unit may be programmed for either 2 or 3 aspect signals, and for either common anode or common cathode signals. Once programmed, the unit remembers the selections, although it may be re- progarmmed for different selections if desired. Detection is by an infra-red LED and phototransistor, which are mounted on a separate small PCB. (See the module D2IR) The time the unit remains in each aspect after a train has passed may be selected via jumpers to be approximately 7.5, 15, 22.5 or 30 seconds.

Kit price for RK-SSS: $19-50
Kit price for RK-SSSP: $24-50

All kits available from :
Aztronics Pty Ltd       Phone 8212 6212
170 Sturt St,                     Fax 8212 4212
Adelaide, SA, 5000.                                

Click here to go to Aztronics web site

Information:         David Crosby

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Last updated 3rd February, 2017.
(C) D. Crosby, April, 2011.