BC-3500 Series - Rowe International

BC-3500 Bill and Coin Changer
Sheet 3: Output Circuits
All output circuits, except the transport transmissive/reflective LED driver circuit, are inactive when the switched +12
VDC supply is OFF. This keeps all the motors, solenoids, and coils in the machine from operating when the machine
is turned ON and OFF, or whenever the RESET line from U21 is LOW.
TRANSPORT MOTOR CONTROL
The transport motor drive comes in to U6B Pin 3. U6B buffers the signal and inverts it through U11C, applying it
to the base of Q5. the transport motor is a DC motor that runs on +12 volts. Motor speed is controlled by switching
Q5 ON and OFF based on the transport motor drive signal. The transport drive signal is not a constant DC voltage
applied to the base of Q5 but a switching signal. If the motor is running too fast, Q5 is turned OFF; if the motor is
running too slow, Q5 is turned back ON.
The transport motor direction is controlled through relay K1. When the relay is in the normal de-energized position,
as shown on the schematic, the motor will run in reverse when Q5 is turned ON. The transport motor runs in the
forward direction when relay K1 is energized. The transport motor direction comes from the processor on Sheet
1 into Pin 5 of U6. It is inverted through U7, then applied to relay K1. Diode D2 suppresses back EMF from K1’s
coil as it de-energizes. D6 and D7 do the same thing for the motor coils when the motor is turned OFF.
HOPPER MOTOR CONTROL
All three hopper motor circuits operate in the same manner, so only the left motor circuit will be discussed.
A low at U11A Pin 1 causes Pin 16 to turn OFF. No current flows through the LED half of U4, so no gate current
is provided to Q3. Without gate current, Q3 stays OFF, keeping the hopper motor OFF. When U11A Pin 1 goes
HIGH, Pin 16 switches to ground, turning ON the LED in U4. Current flows in U4 Pins 4 and 6, supplying current
to the base on Q3, turning Q3 ON. When Q3 is ON, the hopper motor will run.
WARNING:
The hopper motors run on 120 VAC and can cause severe electrical shock. Be very careful
whenever you work with these circuits.
LED DRIVE
The LED drive signal controls the intensity of the reflective-transmissive LED in the transport. The light is similar to
the transport motor in that it is not driven from a constant DC voltage, but is pulsed. If you look at the LED in the
transport, it looks like it is on constant, but it is not. It is pulsing. By changing the duty cycle of the pulse, the brightness
of the LED can be controlled.
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