TURNOUT CONTROLS
TC-1, TC-2
211 RocBaar Dr., Romeoville, IL 60446
(815) 886-9010 FAX: (815) 886-9076
Electronics for Model Railroads
GENERAL DESCRIPTION: The CIRCUITRON TC-1 and TC-2 Turnout Controls provide automatic
activation of any dual-coil type switch machine when used in conjunction with any CIRCUITRON
Detection Circuit. Both units provide short, high-current pulses to the switch machine, protecting the
coils from burnout. The TC-1 has two control terminals and may be used to control both directions
of a turnout. In this way, the output from one Detection Circuit may be used to throw a turnout one
way, and the output of another Detection Circuit may be used to throw the turnout back. The TC-2
is CIRCUITRON’s Turnout Direction Alternator and it has only a single control terminal. When the
control terminal is connected to a Detection Circuit, the switch machine will be thrown one way the
first time a train is detected, and then the switch machine will be thrown the opposite way the next
time a train is detected. In this way, trains can be made to travel alternate routes around a layout,
automatically. Both the TC-1 and TC-2 require a 12 - 18 volt AC or DC input for proper operation.
The outputs on the TC-1 and TC-2 can activate one or two switch machine coils at the same time
depending upon the style of switch machine and the input voltage of the circuits.
CIRCUIT DESIGN: Both the TC-1 and TC-2 have capacitor discharge type outputs for high-current
snap-action of switch machines controlled by them. The capacitor is charged by a 200 ohm resistor
which will limit current to the switch machine should a circuit failure occur. The TC-1 contains two
identical one-shot multivibrator circuits that produce an output pulse of fixed length when the
corresponding control terminal is grounded. This output pulse drives a power darlington transistor
connected common emitter which connects the coil of the switch machine(s) to ground for the
duration of the pulse. The capacitor discharges rapidly through the switch machine coil and then
recharges in 2-3 seconds to await the next cycle. The TC-2 outputs are the same as the TC-1’s, but
the TC-2 also contains a toggle flip-flop circuit that changes states each time the input is activated.
There is additional conditioning incorporated in the circuit in the input section that is used to clean up
any oscillations that might be present from the output of the Detection Circuit that might create false
triggering of the circuit.
INSTRUCTIONS: Please refer to the diagrams for labeling and Opto-Sensor locations. The TC-1 or TC-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.
1) Mount the circuit board in a convenient location near the switch machine to be controlled. A
section of CIRCUITRON’s PCMT makes this a simple task, or the mounting pads may be drilled
out at the corners of the board and the circuit mounted with screws.
2) Connect a 20 gauge or heavier wire to the common terminal on the switch machine (see specific
instructions packed with your switch machine) and run it to the terminal on the circuit board
labeled [OUT].
3) Connect a 20 gauge or heavier wire to one of the remaining terminals on the switch machine and
run it to the terminal labeled [1] on the circuit board.
4) Connect a 20 gauge or heavier wire to the remaining terminal on the switch machine and run it to
the terminal labeled [2] on the circuit board.
5) Connect the Control Terminals ([C1] & [C2] on the TC-1, [C] on the TC-2) to the output(s) of any
CIRCUITRON Detection Circuit using light gauge wire. The DT-4 is ideal for this application. The
Opto-Sensor supplied with the Detection Unit should be located at the point where it is desired to
have the switch machine activated. In this way, the switchpoints will be thrown when the first
piece of rolling stock passes over the Opto-Sensor.
6) Connect a source of 12-18 volts AC or DC to the INPUT Terminals. CAUTION: See Notes Below
7) Manual pushbuttons may be connected as shown in the diagrams below.
