Do More

This small circuit can be used to control model railway turnouts operated by AC voltages. A logic level in the range of 5–12 V can be used as the control signal. The coils of the turnout are switched using triacs. Changes in the logic level of the input signal are passed on by the buffer stage built around T1 and T2. The buffer stage is included to boost the current available at the gates of the triacs. If the input goes high, this positive change is passed through via C1. That causes a positive current to flow through D2 (D2 is reverse biased) to the gate of T3. That triac switches on, and power is applied to the turnout coil. Circuit diagram: Model Railway Turnout Control Circuit Diagram This situation persists until C1 is fully charged. No more current flows after that, so the triac does not receive any gate current and switches off. If the input is set low, a negative current flows briefly via C1. It can flow through D2, but not through D1. T4 is switched on now, and the other turn...

Short circuits in the tracks, points or wiring are almost inevitable when building or operating a model railway. Although transformers for model systems must be protected against short circuits by built-in bimetallic switches, the response time of such switches is so long that is not possible to immediately localise a short that occurs while the trains are running, for example. Furthermore, bimetallic protection switches do not always work properly when the voltage applied to the track circuit is relatively low. Circuit diagram : Model Railway Short-Circuit Beeper Circuit Diagram The rapid-acting acoustic short-circuit detector described here eliminates these problems. However, it requires its own power source, which is implemented here in the form of a GoldCap storage capacitor with a capacity of 0.1 to 1 F. A commonly available reed switch (filled with an inert gas) is used for the current sensor, but in this case it is actuated by a solenoid instead of a permanent magnet. An ad...