Inexpensive (Cheap) Automatic Reversing Circuits

  This page presents simple, low cost - Automatic Reversing Circuits - that use inexpensive or old DC train set power packs as power supplies and to control the top speed of the train.

  A 555 timer IC controls waiting times. Diodes and gaps in the track circuit are used to trap the train at the ends of the track.

1st Inexpensive Reversing Circuit


  The power supply circuit provides power to the track and has a 12 volt power source for the 555 timer IC that controls the waiting time at each end of the track.

  NOTE: The circuit does not know when or how fast the train is moving, therefore the timer's cycle times must also include the time for the train to travel along the track in either direction. For example it the train is to wait for 30 seconds at the end of the track, the timer will be set for: The time to travel to the end of the track + 30 seconds.

  The reversing switch on the power pack itself is only used to set the initial travel direction of the system or to 'switch ends' if the waiting times are not equal.

  The calculator at the following link can be used to determine values for resistors R1 and R2 and capacitor C1. (LM555 - Astable Oscillator Calculator)

2nd Inexpensive Reversing Circuit


  The basic track circuit provides continuous back and forth operation of the train with diodes and gaps to stop the train at each end of the track.

  Also shown is an optional LED that will show when the train has been trapped at the end of the track.

  The next diagram shows how to provide increased stopping distances for trains with head-end power. The longer stopping sections can be switched if the train is reversed.

3rd Inexpensive Reversing Circuit


  This track circuit uses diodes and gaps to provide a crude form of speed control.

4th Inexpensive Reversing Circuit


  This circuit will stop and start the train at a station located on the reversing track.

  This circuit is as simple as possible, using the bottom section of a 556 timer as a photodetector and the top section as the delay timer.

  The timing circuit takes its control and track power from the power supply circuit on this page.

  NOTE: When using this circuit, there are other things to consider, such as; train length and whether the locomotive has all wheel pickup. These can affect the placement of the gaps and phototransistors.

5th Inexpensive Reversing Circuit


  In this circuit the train only moves when S1 is pushed. After a set waiting time the train returns to its start position and then waits.

  The 555 timer in this circuit is configured as a monostable oscillator. The SPDT switch allows the circuit to be changed from normal operation to out-and-back operation. Two 555 timers are indicated but a 556 timer can also be used.

6th Inexpensive Reversing Circuit


  The Flip-Flop circuit depends on the type of switch machine motor used. An example for a slow motion type motor is shown below.

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Please Read Before Using These Circuit Ideas

  The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.

  If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

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07 September 2010