Brian
I have a PC104 card which is really just a single board Pentium PC compter
with connectors for video, keyboard, mouse, serial, IDE drive, 10/100 network,
and a Disk-on-Chip socket all on a card that is 3.5 inches square.
I run Windows98, but any Intel OS could be used. Other cards can be
connected to the main card with a 104 pin buss, so you buy add-on cards with
things like analog to digital converters, and digital I/O, even GPS and Radio
modems. I have a 30 pin Digital I/O add-on that lets me read switches and
encoders, and control relays with the addition of a driver chip. The code
to read and write the I/O lines is good old VB that uses an API that came with
the Digital I/O card. I have a 3rd PC104 card that is a DC to DC converter
that allows me to power the PC104 stack and an IDE hard
dive from an 8 to 30 volt DC supply. All stacked
together the PC104 stack is about 2 inches high. The price tag for
everything was about $600 and everything but the power supply came
from eBay. I was using this setup to run a small autonomous robotic
vehicle and I programmed and complied directly on the PC104 by linking it
to my laptop with PCAnywhere. The down side to this is of course the
startup speed should the system crash. If your only monitoring
systems then perhapse that is acceptable.
Given a choice I'd go with Cliff's setup, but since I can not afford that,
I actually prefer the OOPic solution. The code is VB style, the restart is
fast, it has both analog and digital I/O, you can expand it by adding
a second unit. The units can be networked togther, they can be networked and
intergrated to you laptop, and at $89 pluss $20 for the LCD Display, and $5
for a joystick, you sure not going to beat the price.
Best wishes
Doug Jackson
In a message dated 4/2/2005 9:34:20 PM Central Standard Time,
dr_redus@devtex.net writes:
Brain,
I am not aware of any.
Cliff
----- Original Message -----
Sent: Saturday, April 02, 2005 7:44
PM
Subject: Re: [PSUBS-MAILIST] computers
in subs
Cliff,
Do
you know if there would be any way to program a workable system using
VB , I guess you would use a lap top?
Brian
----- Original Message -----
Sent: Saturday, April 02, 2005 9:29
AM
Subject: Re: [PSUBS-MAILIST]
computers in subs
Doug,
My background is in mechanical engineering. This was my first
hands on project with a PLC. I found working with the PLC to
be straight forward. The documentation that comes with the
Automation Direct is detailed and very usable with lots of examples.
Also the tech support from Automation Direct was great. I think this
is generally true for all the PLC suppliers. Anyone that has done
any programming in C, VB or even FORTRAN (I'm dating my self) would have
no problem picking up PLC ladder logic. My starting point was to make
a list of the what I/O I wanted in my boat such as, for example, an analog
input would be a pressure transmitter for ambient water pressure or tank
pressure. A digital input channel would be something like the hatch
switch or a limit switch or a button on a joystick. An Analog output
would be like a PWM signal to a proportional pressure regulator and
digital output would be, as an example, a coil on a solenoid
valve for air to blow the main ballast tank. After you know how many
input and output channels you will need, then you can look at the PLC
modules and decide how many you need of each. This will set the
number of slots you will need in the PLC base. My suggestion would be to
have a least one open slot for future changes. After plugging in the
modules, it is a matter of programming each module. My learning
curve was greatly helped by a fellow PSUBer, Alec Smyth, who sent me a
copy of his ladder logic. By studying what Alec had done and reading
the documentation from the PLC vendor, I was able to come up to speed
without to much grief. I did find the instruction set available on
PLC's to be primitive relative to higher level languages such as C or
VB. Most sensor manufacturers offer either 0-5VDC output or 4-20mA
outputs. After discussions with an engineer that does a lot of
mobile automation work, I choose to go with 0-5VDC for my
sensors. Anyone with basic skills in electronics ( can use a
multimeter and can solder) can pick this up. As to PC104
experience, I have none. One suggestion I would make is to stick
with one PLC vendor for all the modules and the touch screen
display. This makes trouble shooting a lot easier. One other
point, if you have any sensors that require RS232 communication in ASCII,
you have make sure the CPU module you pick support receiving ASCII as some
do and some do not. One of the good suggestions I received from a
fellow psuber that had fabricated a psub was to wire up all the
instrumentations and equipment on the bench in approximately the correct
location prior to installing in the boat. This proved to
be very helpful in debugging everything and in making up the
wiring harness with disconnects. Part of my interest in building a
psub was to come up to speed on PLCs and instrumentation. This part
of my fabrication has been a lot of fun. I did not buy any specific books
on instrumentation. I did do a Google search on basic
instrumentation wiring and found quite a bit of guidance. The real
work in using a PLC as the onboard computer has nothing to do with the
PLC, it is having a good plan of how each ship system is going
to operate and interface with the overall design.
Cliff
----- Original Message -----
Sent: Saturday, April 02, 2005 9:03
AM
Subject: Re: [PSUBS-MAILIST]
computers in subs
Cliff
Yup, that is out of my budget. But I have a friend, and fellow sub
builder that wants to go all out on his control and monitoring
system including the touch screen. So what is the leaning curve
for PLC and the required electronics of sensor integration? And
what web, book, and or training resources would you recommend for
someone with beginner digital electronics abilities and good object and
structure programming skills, but no PLC?
Is automation control your field of work, or did you develop this
skill for your sub? And so do you have experience with PC104 ( www.pc104.org) and would that be a
better approach for someone with C or VB experience but no PLC?
Thanks again
Doug
In a message dated 4/2/2005 8:38:24 AM Central Standard Time,
dr_redus@devtex.net writes:
Doug,
The cost breakdown for the Automation Direct PLC system on my
boat is: PLC hardware $2183, Software $394, color touchscreen display
$745 and joystick $469 for a total of $3791. If you are patient and
know what you want, you can pick up I/O modules on Ebay at a
significant discount. As an example, an Ebay search string
Automation Direct will usually turn up a list of available PLC
modules.
Cliff
----- Original Message -----
Sent: Saturday, April 02, 2005
12:41 AM
Subject: Re: [PSUBS-MAILIST]
computers in subs
Simon,
I know it's out of my league, but out of curiosity, what is the
price tag for that setup?
Thanks --Doug J
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
----- Original Message -----
Sent: Friday, April 01,
2005 5:08 AM
Subject: [PSUBS-MAILIST]
computers in subs
NEW
TOPIC!!
Who uses onboard computers on their subs? Are you
using modified
trimix SCUBA computers, or homebrew type
stuff?
Simon,
You mean a dive computer or a normal? On a
1 atm sub a deco computer makes no sense.
If my sub is operational again; I consider
a pocket pc for instument reading ,listing checklists, gps
navigation and as video camera display/capture.
There are probably more possebilities and
it might save space.
disadvantage: not water
resistant
regards Emile
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