GENERAL DESCRIPTION: The CIRCUITRON AR-2 is a sophisticated, integrated circuit design, automatic
polarity reverser for use on point to point layouts in any scale. The AR-2 provides 5 amp reversing capacity and
also incorporates an adjustable time delay circuit that will stop a train at each reversing point for a set period of
time before reversing the direction. This time delay is adjustable from 0 to over 1 minute. In addition, a terminal
is provided for external activation of the time delay circuitry without reversing direction. This terminal can be
connected to a panel pushbutton or to the output of one of CIRCUITRON’s detection units to permit stop and
delays at any point. If a DT-4 Rolling Stock Detector is used in conjunction with the AR-2, up to 4 intermediate
stopping points can be established between the reversing points. The AR-2 utilizes Opto-Sensors mounted in the
track to detect the train. There are no modifications to rolling stock necessary, and the AR-2 will detect un-
powered as well as powered rolling stock. The AR-2 requires a 12-18 volt AC or DC power supply for proper
operation.
WARNING
MANY MODERN POWER PACKS HAVE ACCESSORY TERMINAL VOLTAGES THAT EXCEED 18 VOLTS, ESPECIALLY WITHOUT
ANY LOAD. INADDITION, THE VOLTAGE LISTED ON THE POWER PACK LABEL IS OFTEN-TIMES MISLEADING. WESUGGEST
THAT YOU MEASURE THE POWER PACK OUTPUT WITH AQUALITY VOLTMETER BEFORE CONNECTING THE AR-2.
EXCEEDING 18 VOLTS ON THE SUPPLY TERMINALS TO THE AR-2 WILL LIKELY CAUSE DAMAGE TO THE CIRCUIT OR
RELAYS. THIS WILL VOID YOUR WARRANTY.
INSTRUCTIONS: Please refer to the diagrams for labeling and Opto-Sensor locations. The AR-2 can be
connected with .110" solderless connectors or by soldering leads directly to the terminals on the printed circuit
board. If soldering, use a small pencil-type iron and electronics-grade rosin core 60/40 solder (available at Radio
Shack). Use only as much heat as necessary to obtain a good joint and do not wiggle the terminal until the
solder has cooled completely. A section of CIRCUITRON’S PCMT can be used for simple, snap-in mounting of
the circuit board or you may drill holes in the mounting pads in the corners of the board and mount the AR-2 with
screws and standoffs.
1) Mount the AR-2 in a convenient location.
2) Install the 2 Opto-Sensors at the points you wish to have the train reverse direction following the
instructions packed with them.
3) Connect one lead from each of the Opto-Sensors together with light gauge (22-24) wire and run it to the
[SD] terminal on the circuit board.
4) Run individual wires from the remaining leads of Opto-Sensor 1 and 2 to the [S1] and [S2] terminals on the
circuit board.
5) If it is desired to have more than one reversing point per side, such as on a siding, additional Opto-Sensors
can be connected in series up to a total of three per side. See Figure 2.
6) Connect wires from the [OUT] terminals to the track as shown.
7) Connect the [IN] terminals to the variable DC output (TRACK POWER) of a throttle or power pack.
8) If manual reversing capability is desired, connect pushbuttons between [S1] and [-] and [S2] and [-] as
shown in Figure 2.
9) Connect the [+] and [-] supply terminals to a 12-18 volt AC or DC power source. If you have both
available, use DC. SEE WARNING ABOVE BEFORE MAKING THIS CONNECTION.
10) If manual delay activation is desired, connect a pushbutton or other momentary switch between the
[DELAY] terminal and the [-] supply terminal. If automatic stop and delay action is desired, connect the
[DELAY] terminal to the [OUT] terminal of a CIRCUITRON detection unit such as the DT-4.
ADJUSTMENTS: Be certain that the room lighting is at the level it will be at during the operation of the layout.
1) Rotate the Delay Adjustment [PD] completely counter-clockwise. This will eliminate the delay section of
the circuitry.
Automatic Reverse Circuit
with Adjustable Time Delay
AR-2 rev. B
211 RocBaar Dr., Romeoville, IL 60446
(815) 886-9010 FAX: (815) 886-9076
Electronics for Model Railroads
NOTE: If you already have a regulated 12 volt DC power supply (such as the CIRCUITRON PS-2) installed, and wish
to use it with your Revision B AR-2, it will be necessary to bypass the voltage regulation portion of the circuit. This is
done by connecting a short jumper wire between the bypass terminal labelled [BP] and the Sensor Drive terminal
labelled [SD].
CAUTION: Do not make this connection unless you are absolutely certain that your power supply is REGULATED at 12
volts DC output. The accessory terminal outputs of most all power packs are NOT regulated. Failure to heed this
warning will almost certainly result in destruction of components on the AR-2 which will VOID your warranty.
