Appendix C - Theory Of Operation; Theory Of Operation - Graco PGM Instructions - Parts Manual

Appendix C - Theory of Operation

Theory of Operation

Input and Output Signals
Terminology
For the purpose of this document a digital signal is said
to be SET when voltage is present (or above the mini-
mum threshold). A signal is said to be RESET when the
signal voltage is not present (below minimum threshold).
Devices are referred to as SET when they are in their
energized or active state.
Digital Inputs
Dispense Start - This is the Dispense Signal. The PGM
unit will attempt to dispense at either the commanded
flow rate while this signal is SET, dependent on mode.
Control On - This input is reset when the E-stop button
is pressed.
Job Complete - This input can be used to signal a job
end.
NOTE: The dispenser ready signal is an important sig-
nal for the automation to monitor. When the dispenser
ready output is not on, the LT may not be responding to
requests from the automation. This could create the sit-
uation where the automation is running production, but
the PGM is not dispensing any material.
Dispense Valve Solenoid - This signal will be set to
energize the dispense valve solenoid at the beginning of
a dispense cycle.
3A5185B
Fault Present - This bit is RESET under the following
conditions:
• No Faults (alarms or warnings) are active.
In Cycle - In Cycle signal is set at the beginning of a dis-
pense cycle. It is reset at the end of the dispense cycle.
The dispense cycle can end in two ways, depending on
how the Job End mode is set:
• If the Job End mode is set to remote, dispense cycle
ends when the job complete signal is received from
the automation I/O.
• If the Job End mode is set to Display, dispense cycle
ends when the Job End delay timer expires. See
Appendix A - User Interface Display on page 82.
Analog Input
Flow Command - The flow command signal input rep-
resents flow requests. The voltage must be between 0
and 10 volts DC. The 0-10 volt signal is interpreted as a
relative 0-100% flow command signal. The system must
be in Remote Mode for this input to be used.
See the Accessory Parts on page 74.
Appendix C - Theory of Operation
101