Valco Cincinnati VC3500, User Manual

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VC3500/VC3700 Troubleshooting Manual
Valco Cincinnati Page 16
PAL Logic
A 20V8 PAL (U9) provides all logic between input and output signals. PAL equations and
the equivalent gate logic circuit is included on Schematic 999xD151-202.
Scanner and Encoder Inputs
A 12 VDC on-board regulator provides an isolated power source for scanners, encoder, Jam
signal, and Dump Valve Control signal. Scanner 1 through Scanner 4 and Encoder signals
should have open-collector, active low outputs. These signals each have a small filter circuit
(3-terminal capacitors), then are optically-coupled to logic circuits referenced to digital
ground (symbol denoted by an open triangle). These logic signals are then transferred to 1)
the LED board to drive status indicators, and 2) the CPU board for signal processing.
The 3-terminal capacitors are provided to pass fast transients to ground without damaging
other components. Input protection diodes to ground ensure that a large negative spike will
not cause damaging currents to flow through the opto-isolators. The encoder input circuit
requires a fast response of 40 kHz, so a 6N137 device was used.
At the maximum rate of 2000 feet per minute, using a 1000 pulse encoder, and a
10 inch wheel;
(2000 ft/min) * (100 pulses/inch) * (1 min/ 60 sec) * (12 in/ft) = 40 kHz
All other opto-isolators use the slower 2630's.
Jam Output
The Jam Output signal at J6 uses an open-collector circuit to energize the coil of a 12 vdc
relay when a jam condition occurs. This signal is turned off (goes to 12 vdc) when the parent
machine speed drops below minimum speed. This circuit can drive a maximum load of
500mA. This output signal is normally connected to J1 of the Machine Interface Relay board
(151xx404) to drive relay RL1. This relay provides an immediate machine stop.
A delayed stop for special machine control is available when Jam Relay Cabinet (084xx020)
is used. Both a standard relay (for immediate stop) and a timer relay (160xx183) is installed.
Dump-Valve Control Output
The Dump-Valve Control Output signal at J8 uses an open-collector circuit to normally
energize the coil of a 12 vdc relay. When machine speed falls below minimum speed, this
signal is turned off (goes to 12 vdc) to turn off the dump valve. This circuit can drive a
maximum load of 750mA.
Valve Driver Signals
The signal to fire a valve can be sent to the Valve Driver board when one of the following
conditions occur (controlled by gates U9,10):
1. The "/PURGE" signal on connector CO1 (derived from the front panel Channel
Enable switch) must be low, or
2. The "/VAL-CH" signal on connector CO1 (derived from the front panel Channel
Enable switch) must be low AND the "/CHAN-OUT" signal on connector CO2
(from the Channel Logic IC on the CPU board) must be low.
The outputs of valve drive signals as well as Peak and Hold voltage status signals from the
Valve Driver board are also isolated to provide noise immunity for logic and analog circuits.
The ground reference used for valve driver signals is denoted by a filled-in triangle.