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Simon,
For the 1 atm sub I have under fabrication, I am
using an Automationdirect (http://web4.automationdirect.com/adc/Home/Home),
DirectLogic 205 series PLC (Programmable Logic Controller) with a 6" color
touch screen display which is used to interface with the controller
and for all gage displays. The PLC base has 9 modules, 1 CPU, 3 analog
input, 1 digital input, 1 RTD input, 1 analog output and two relay output
modules. The PLC is currently configured with 20 analog input channels, 12
digital input channels, 4 RTD temperatures inputs, 4 analog output channels, and
18 relay output channels. The CPU module (DL 260), which is about
the size of a bar of soap, has two RS232 ports, one of which is used to
connect to my compass/roll/pitch sensor and the other is connected to the touch
screen display. A dual axis joy stick is used for roll and pitch
analog input to the PLC and a potentiometer on the rudder pedals is
used as an analog input for yaw control. The joystick has 6 switches
that I use for blowing and flooding the MBT and VBT as well as moving the
trim weight forward or aft via a power screw driven by a hydraulic
motor. This setup gives me fly by wire capability. A laptop
PC was used to write the ladder logic, design the screens and download the
ladder logic and screens into the PLC. All is working fine on the bench and I
found the system to be quite flexible in changing inputs and outputs to the PLC
and modifying display screens.
A PLC was chosen over a hardened PC for robustness
and to minimize space. The PLC is powered from either the main battery bank (120
VDC) via a DC-DC converter (120 VDC to 24 VDC) or from an independent
emergency battery pack (24 VDC).
Cliff
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