Re: [PSUBS-MAILIST] Sensor Interfacing

[Michael Wright <mwright@smallip.com>]

For interfacing sensos to a PC I would look at the Dallas/Maxim IC 
1-wire equipment.  The devices connect to the PC via serial port.

http://www.embeddeddatasystems.com/

for I/O Devices:

http://embeddeddatasystems.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=IO

One advantage of going with 1-wire is that since 100+ devices connect 
via a 1-wire plus ground network it limits the number of hull 
penetrations needed.

http://www.maxim-ic.com/1-Wire.cfm


I haven't used National Instruments Products because they were simply 
beyond the budget for what we were doing.


If you want to build your own interface I would note that having used 
the BasicX and PIC-Basic Pro (a lanuguage identical to basic stamp 2) I 
would not consider using anything based on Basic Stamp.  BasicX uses 
BXBasic, which is VB 6 with most of the stupidity removed.  The cost for 
a BX Kit is $100 and the IDE is free.

The Netmedia BasicX units were quite effective for the vehicle 
Depth-Heading systems and remote monitoring applications I used them 
for.  Though the BasicX units can multitask, their limited RAM (400 
bytes) makes it something to be careful of.  I would also note that 
their on board serial port does 0V to 5V signalling rather than true -5V 
to +5V, which is only a problem if you were connecting it to a dumb 
device (such as a Fiber-Optic transceiver) and can be solved by putting 
a maxim RS232 chip inline.

If you already program in C or have time to learn, don't pay the extra 
money for the limitations of anything programmed in any basic variant.


All that said I would also note that one of the design constraints I was 
under was that the systems had to be adaptable to work standalone (no 
PC).  Given the option of a scratch redesign with a PC, I'd use 1-wire 
sensors directly to it (well probably four seperate 1-wire networks (2 
redundant for outside the hull and 2 redundant for inside the hull).

Good Luck,

mike

Warren Greenway wrote:

> This one I know, since I am an embedded systems
> engineer. First, the direct to PC interface will be
> either one of the most expensive, or one of the most
> difficult you can tackle. Second, yes, there are 
> hundreds of options in the way of PCI boards (not AGP,
> that is graphics). Interfacing through the RS232 Port
> is what I would recommend. This is the easiest,
> cheapest
> and most flexible. To do this, you will need some
> basic
> electronics and programming skills (or you get back to
> VERY expensive). The code and hardware is very simple
> if you go with the MSP430F1121 (or related MSP430).
> This
> is the easiest series of MCUs to program. The devel
> kit is $49 from TI. They have ADCs and UARTs built in.
> You simply fire up the ADC, take a reading, fire up
> the
> UART, and transmit the reading to any RS232 device you
> want. You can also recieve and execute control
> commands.
> This may sound a little wild, but believe me you get 
> the most bang for your buck in the MCU world. Another
> simpler, and much less powerfull option would be the
> Basic Stamp or BasicX. Both of these can also provide
> a cheap interface to your PC. 
> 
> Warren.
> --- peter  mckellar <mckellar@earthlink.net> wrote:
> 
>>Hi,
>>
>>Apologies in advance for shamelessly displaying the
>>depths of my ignorance.  I have a general question
>>on interfacing sensors to PCs.
>>
>>I know that many of the control systems built by
>>contributors are custom PLCs etc.  I also know that
>>many pressure sensors, oxygen guages are mechanical
>>and avoid these problems.
>>
>>I however was hoping to use (basically)
>>off-the-shelf components hooked into a standard PC. 
>>Is this even possible?
>>
>>What I'm talking about is standard PC boards that
>>slip into a PCM, AGP etc type slot and they have a
>>wire attached to a probe that is either naked or
>>mounted somewhere in the cabin, or stuck through the
>>hull.
>>
>>Todays research has centred around sensor suppliers
>>(specifically ceramic, piezo-electric or MEM based
>>at this stage) but I can't seem to fathom how these
>>are interfaced.
>>
>>1.  Is there a standard PC board protocol/usb
>>attachable mulitplexor that allow me to buy sensors
>>and attach them either individually, daisy-chained
>>or as part of a sensor array, mixing and matching as
>>I desire?
>>
>>2.  Is there standard software (maybe html based?)
>>that comes with these like they supply for routers,
>>or for that matter, is ANY software ever supplied
>>with these devices?
>>
>>3.  do any come with an IP address that allows me to
>>plug them straight into an onboard lan
>>
>>I can see this could get really ugly :(  i can do
>>wonderful things with software, flip bits, do
>>boolean stuff, draw truth tables, but i've never
>>burnt a rom in my life and can't even solder :(
>>
>>I guess I'm wondering if I can do plug-n-play things
>>or if I should look at enrolling in an electronics
>>(hands-on) course.
>>
>>Any suggestions or comments?
>>
>>peter
> 
> 
> 
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