Blinking Auto-Reverse Controller

Revised 2-28-06

Please note that the photos and information below are based on a prototype of this controller.  The finished board and controller will be very similar but not identical to what is shown here.

  • The Blinking Auto-Reverse Controller (BARC) makes running trolleys and other point-to-point rail cars a simple and enjoyable experience

  • Even though the unit was initially called the "Basic" Auto-Reverse Controller  its microprocessor brain gives it a host of features in a small package

  • The only connections are to your DC power supply and to the track.  The normal cut rail and diode that such systems traditionally use must be installed at each end.

  • Note that this controller does not provide gradual acceleration or deceleration.  The power to the trolley is either on or off.  It is recommended that low speeds be used with this unit to obtain a realistic experience. 

  • Features

    • You supply DC power from your transformer to the input pins on the relay -a minimum of 7 volts is needed to operate the unit

    • A potentiometer is used to set the time that the trolley will run between reversals.  This time can range from a few seconds and over 4 minutes.

    • The train or trolley goes to one end of the track, stops where it enters the diode protected section and waits until the relay reverses the power
    • When the relay reverses the trolley goes to the other end and the process repeats
    • A set of 3 LEDs is used to show the time setting and the time remaining as the trolley runs
    • The same LEDs also show the number of "laps" or reversals that have taken place.
    • A jumper controls whether the time is always the same or is changed randomly

  • Track Preparation

    • A section of track must be cut and a diode must be installed across the cut at each end of the track

    • Both track sections need to be cut on the same rail and both diodes must be installed with the same polarity, that is the band on the diodes must point in the same direction.  Note that the drawing above is for a G scale layout.  If you work with HO the diodes must have their bands pointing in the opposite direction.

    • Click here for more information on preparing track

  • Power Connection

    • Power from your DC train transformer can be connected directly to the power terminals on the board

    • The power from your transformer goes to the blue female connector labeled "In"

    • The track is connected to the male connector labeled "Out"

    •  

  • The BARC does not control the speed of your trolley, only its direction.  If you wish to manually adjust the speed of your trolley or engine you can connect the BARC to the variable output from your power supply.  Note that the BARC will shut down and reset. if the voltage goes much below 7 volts.

  • The voltage regulator on the board can get very hot if more than 18 volts is supplied.

 
 
 
Setting Time
  • When the unit is first turned on the 3 red LEDs flash together 15 times. 
  • During this flashing you have an opportunity to change the time setting. 
  •  The potentiometer can be adjusted with a small screwdriver to make time adjustments
  • Turning the potentiometer counter clockwise decreases the time and turning it clockwise increases the time
  • The time range is from a few seconds to 255 seconds, a bit over 4 minutes.
  • In the photo below the black arrow on the potentiometer is very close to the center of its range of movement.  This would give a time very close to 127 seconds.

  • If you turn the adjustment potentiometer during the flashing the 3 LEDs will begin to flash out the time in seconds.
  • The LEDs are labeled 1, 10 and 100.  To indicate a time of 135 seconds the 100's LED would flash once, the 10's LED three times and 1's LED five times. 
  • Each time the potentiometer is moved the time will change the time and the unit will flash out the new setting.
  • If you stop adjusting the potentiometer and allow the time to be flashed out five times the time will be stored and the unit will start timing.
  • Note that time can be adjusted at any time during the BARC's operation by turning the potentiometer a bit either way.  This will put you back in the mode described above.
Random Time
  • If the jumper is installed on the two pins labeled "random" the timing changes and adds an element of randomness.
  • The random time is computed using this formula:  1/2 of the time selected is added to a random number between 1 and 1/2 of the time selected.
  • For example, if the time were set to 200 seconds the random times would be between 101 and 200 seconds.  If 120 were set the random time would be between 61 and 120 seconds.
  • Using this formula insures that your trolley will have enough time to traverse the track before it reverses since the time is never less than 1/2 of what you have selected.

 

Getting started

  • Install cut / diode equipped track at each end of the line of track

  • Connect the unit to the AC or DC output of your transformer.  This may be a constant or a variable direct current power output.

  • Connect the output of the unit to the track

  • Place a trolley, small engine or rail car on the track

  • Turn on the power

  • Adjust the time

  • After the BARC initializes your engine will begin its journey in one direction or the other

  • Once it hits an end it will delay, reverse and continue
 Time Reported During Timing
  • As the BARC operates it flashes out the time remaining until the trolley is reversed. 
  • You may notice that the flashing will frequently skip a second or two as it reports, for example, 33, 32, 31, 30, etc.  This happens when the time needed to flash out a report exceeds one second. 
Laps Completed Report
  • Each time the time count reaches zero the BARC reports the number of times the unit has reversed the trolley.  You can think of this as the number of "laps" that have been completed.
  • The report is similar to the time remaining report except that all 3 LEDs flash before and after the laps report and the report is flashed out somewhat more slowly than the time remaining report.
  • If the number of laps exceeds 999 the counter will continue to report by flashing the 100's LED correctly.  If you are on the 1345 lap, for example, the 100's LED will flash thirteen times, the 10's four times and the 1's five times.  If you let it run for a few weeks it will eventually reset to zero when it gets past 2^16 which equals 65,635!!
 
An Added Bonus!
  • If your computer is equipped with a standard 9 pin serial port you can see the progress of your BARC and see the total laps completed by your trolley.
  • Receiving reports from the BARC involves starting a terminal program, like HyperTerminal.  Set it to 2400 baud, No parity, 8 bits, and one stop bit.   It must also be set to use COM1 (or whatever com port you prefer) rather than a modem.

    The images below show how I set up my computer.  To get started on a Windows 98, 2000, ME or XP computer click Start then All Programs then Accessories then Communication then HyperTerminal.  If HyperTerminal is not there you may have to install it.  For instructions on how to do so just search Google for "Install HyperTerminal".  Here is a sample link on how to do the install from IBM's web site.

    When you first start HyperTerminal you must create a new connection.  Type a name for the new connection (I used Com3 2400) in the Name box.

    Click OK

    In the Connect To box I selected Com3 - you are more likely to be using Com1

    Click OK

    Change the next screen so that it looks like this:

    Make sure Flow Control is set to "None"

    Click OK

    Connect the 9 pin serial plug to your PC's serial port.  The cable is short and may require a serial extension cable.  Plug the 2 pin header into the board where it is labeled "serial" - make sure the white wire on the connector that goes to the board goes to the pin marked "-".

    If necessary click on Call / Call to connect to the port.  Once connected you should see information like that show below on your screen.