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Re: [PSUBS-MAILIST] Integration of instruments:
mike
this is a just comm interface, nmea protocols which are based on rs
232 or rs 422 twisted pair comm are just the industry agreed adress and
value number using fixed ascii values . you can config any lap top to talk
to these devices. the basic protocol is one master and all slaves. Lets
look at the type of integration required in a psub.
instrumentation integration for a psub
instrument protocol value
depth of water nmea ascii
heading nema ascii
gps nmea ascii
depth none 4-20 ma/0-10 volt
tank presssure none 4-20 ma/0-10 volt
o2/co2 sensors none 4-20 ma/0-10 volt
battery voltage none 0-10 volt with dividers
digital i/o none voltage based
input/output
why all the different comm types/ sensor interfaces?
most sensors that only give a single value will be a 4-20ma or voltage
output, while sensors that give more than one value worth of info will have
some type of serial ascii interface. however there are also serial comm to
current or voltage converters especially for depth and heading sensors.gps
has to much info to allow for conversion to single value data types.
integrated consystem costs can be as low as several hundered dollars to
as hgih as 10's of thousands of dollars depending on the bells and whistles.
primary points for system design
1. decide the typeof hmi wanted/human machine interface
lcd screen
lights and buttons
monitor with or without touch screen
2. type of system control wanted
auto depth control
auto heading control
alarm types/ low pressures/ low voltage/flooding
drive system interface
3.type of controller wanted
plc/ programable logic controller
pc based control
pic/micro controller
single function controller
pic this type of controller used is normal based upon the amount of
data needed. Most pics only have four analog chanels but they can be up
graded to more this type of controller is what is used in most of the
electronics what we see today. and is often refered to as embeded contoller.
plc/programable logic controller
these controller are the standard for industrial con systems due to the
large quanity of equipment and options available for them. normally you pick
a manufacture and they will provide all of the equipment /interfaces and
software for the system, you just have to write the control logic. While
pc's are used for the hmi they never controll the process. pc's are
considered to be to unreliable for process control.
pc based control
dont do it/ use a pc for data capture only.
cost consideration vrs skill level
pic's relativly cheap about 100.00 but will require custom circuits to
be designed and the ablity to program the controller using one of several
languages. normally little to non manufacture support.
plc's start at several hundred and go up, a basic system with a basic
hmi can cost several thousand dollars. but allows for multiple type of
sensors without making custom circuits, and the software is normally easier
to write, and most manufastures have great customer support. i prefere allen
bradley for this type of control.
pc's. there are several types of data aqusistion devices and software
for pc,s available on the market today . Ranging from several hundred
dollars to several thousand dollars. as i said before do not use these
systems for control only data storage.
single function controller/ pid controller
as the name says they will control only one funtion/ sometimes two but
that is just two singles in the same case, and do not require software
programing just the tuning and setpoint input. they would be great for an
auto depth control and or heading. and they cost about 500.00$
sorry to get so long winded
rick m
----- Original Message -----
From: "Michael Holt" <mholt@ohiohills.com>
To: "Personal Submersibles List" <personal_submersibles@psubs.org>
Sent: Sunday, December 11, 2005 10:19 AM
Subject: [PSUBS-MAILIST] Integration of instruments:
http://www.worldwidewiley.com/2boat.shtml
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