gohastings.com Hastings Entertainment Cable Box DAVC-4 Manual De Usuario

Page 12 of 17

 

A single set point controls two open collector circuits. Though not the mechanical relays, the two circuits 

called Alarm 1 (P > SP) and Alarm 2 (P < SP) allow physical monitoring of the state of the vacuum with 
respect to the set point. 

Alarm 1 (P > SP), pin #1 (gray), is active when the red LED is ‘ON’ indicating that the pressure is 
above the set point. 

Alarm 2 (P < SP), Pin #2 (brown), is active when the green LED is ‘ON’ indicating that the pressure is 
below the set point.  

The open-collector circuits need to be supplied with their own power and current limiting resistance by the 

end user. The load, controlled by the Open-Collector circuits, must not require voltages higher than those 
specified for the DAVC (12 – 30 VDC) AND must not exceed 500 mAmps of continuous current. See the 
section on Pressure Alarms Pin Out for wiring instructions.  

The alarm set point may be set in one of two ways: 

One, by the measuring the Voltage signal between Analog Signal Common, Pin #6 (violet) and 
Setpoint Level, Pin #5 (white) and setting the voltage using the SP potentiometer until the voltage 
corresponds to the pressure indicated on one of the Pressure Vs. Voltage charts above. 

Two, by using the A2 command to send the set point voltage to the A/D converter in conjunction with 
a P1 command to enable streaming while the pot is set to the desired trigger pressure.  Remember to 
disable streaming by issuing a P0 command and reset the signal source of the A/D converter by 
issuing an A0 command. 

While the SP potentiometer is enabled using the PE command, the value of the set point is read every 

thirty seconds and compared to its previous setting. If the setting has changed, the new setting will be 
stored to non-volatile memory. If the SP potentiometer is disabled using the PD command, then no 
tweaking of the SP potentiometer will have any affect.  

In either Enabled (PE) or Disabled (PD) cases, using the S1=#.## command will re-write a new set point. 

Only if the Potentiometer is Enabled using the PE command, will adjustment of the potentiometer affect a 
previous set point. 

See the section on Serial Communications Pin Out for wiring instructions.  RS-232 communication may be 

established with baud rates of 9600 or 19200 only. The communication parameters of the DAVC are fixed 
at 8 data bits, 1 stop bit, no parity and no handshaking. The command set can be found in the table below.  
Communication with the serial interface of the Digital AVC is via an ASCII data string. The command 
message consists only of a command string and the terminator.  If all components of the ASCII data string 
are valid the command will be accepted and executed.  

In the following examples of syntax codes, the special characters are explained: 

The first characters in each row of the format column represent a command string, either upper or lower 
case command characters accepted. All characters must follow each other in the string with no spaces 
or other characters. 

The characters within wavy brackets { } contain choices for the appropriate command.  

The characters within the symbols < > are the common abbreviations for the one digit ASCII control 
codes which they represent, (e.g.  <CR> represents carriage return). 

All command strings must be followed by the terminator character (carriage return <CR>, also known as 
ENTER).  

When a lower case character is present in an example it represents an option.