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5 Times Around Circuit

5 Times Around Circuit

The 5 Times Around circuit was designed to automatically let an N Scale locomotive and car travel around a loop 5 times and stop for approximately a minute and then repeat the cycle.
Each time the train covers the photocell, which is mounted between the rails, the first LM556 timer section is triggered by the LM393 comparator. This timer is a negative recovery type to ensure that only one pulse is generated for each time the train passes over the cell.

The 4017B divider IC counts the number of times it receives a pulse at its number 14 pin. On the 4th. pulse the number 3 pin goes high and when the 5th. pulse is received this pin will go low and cause the second LM556 timer to trigger.

The second timer controls the length of time that the train is stopped. When triggered its output is high, the relay is turned on and the track power circuit is opened. The length of time that the train is stopped can be changed by adjusting the values of the 470K resistor and the 68uF capacitor.

The train will stop at the location of the photocell, therefore it is placed where passengers would get on the ride.

If no power is connected to the control circuit the train will run all of the time.


The circuit can operate automatically or manually depending on the setting of S2.

In the automatic mode with S2 OPEN the 5 times around cycle repeats itself continuously.

In the manual mode with S2 CLOSED the cycle stops after the train makes its fifth lap. The 5 times around cycle is then repeated each time S1 is pushed. (An easy way to get visitors involved in the action.)

The 4017B integrated circuit can be wired so that from 1 to 9 laps can be made between waiting periods. This is done by connecting any one of the divide by 1 through 9 outputs to the reset at pin number 15. Please refer to a manufacturers data sheet for more information on this device.

The control circuit is powered by a plug in type AC adapter with a filtered DC output that is large enough to operate the relay, 9 Volts at 200Ma. is OK. The N scale train is powered by an old power pack.

It should be noted that when power is applied to the circuit the 4017B will not be at a zero count and the second timer will turn on. Therefore the first cycle will be shorter than those following and the train will not run immediately.

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