Re: Analog to Digital converters/controllers?
- From: "Paul G. Tobey [eMVP]" <p space tobey no spam AT no instrument no spam DOT com>
- Date: Tue, 3 Feb 2009 09:37:00 -0700
I'd like to be able to measure and control external devices. For example:
. Measure temperature of a room
No problem. You generally will do this with a thermocouple, although there
are other temperature-sensing devices that are more-linear for applications
which don't have to deal with very high or very low temperatures. Is there
already a sensor in the room that you want to read or do you want to
implement one?
. Detect if a 24vAC relay is energized
This is a relay that you aren't controlling? I mean, if you control the
relay, you'd know, right? Otherwise, you'd need a 24 VAC input, which is
kind of strange range. We have devices that can do it, but for one relay,
it's expensive.
. Control 24vAC relays
What is the control voltage? Most PC-based (plug-in board), control boards
will have 0-5VDC outputs, which might not drive enough current to control
your relays. You need to know the specs for those relays when you're
looking for hardware to control them. Generally, though, no problem.
. Control a linear actuator
This is a little big vague. You have the actuator? What control signals
does it use?
There are many companies who do this sort of thing. We aren't huge in
linear actuators, although we do have quadrature inputs for reading position
from such things, step #1 in controlling them. We can do the other things
with several different types of devices from plug-in boards for PCs, to
Ethernet-connected systems running RTOS, to programmable Windows CE-based,
Ethernet-connected devices which are modular. Take a look at www.edasce.com
and www.instrument.com, if you're interested.
If you want a magazine for this sort of device to see who's big in the
market, look and Test and Measurement World. I think you can find it at
your magazine shop. There will be ads in there from many folks who do that
sort of thing with various interfaces.
Generally, if you're planning to build your own Windows CE-based device, you
DO NOT want to interface to your measurement/control equipment with USB.
You need USB drivers for any equipment that you want to talk with and almost
no one has Windows CE drivers for their USB devices.
RS-232 is no problem, of course, as you're basically writing your own code
to control things anyway. Our devices have APIs for doing operations like
reading all the analog input channels on a given device or writing all of
the digital output channels, or pulsing a digital channel for a period of
time. The other guys who do this have similar methods that vary depending
on the various hardware architectures. Some offer high-level programming
environments for writing your 'program' graphically, as well as C/C++, etc.
Others may have application environments that automatically acquire data and
store it on disk or something.
Paul T.
"JohnKoz" <JohnKoz@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:45FB0C1A-C8C5-4341-BAC1-ED4348444925@xxxxxxxxxxxxxxxx
Hi,
I'd like to be able to measure and control external devices. For example:
. Measure temperature of a room
. Detect if a 24vAC relay is energized
. Control 24vAC relays
. Control a linear actuator
I'm assuming such devices communicate with standard USB or RS232
interfaces,
I'm open to either, perhaps even Ethernet. Ultimately I'd connect this to
a
CE embedded device, but I could also use it on my development workstation
for
initial experimentation.
I don't know anything about the companies or individual products in this
area. Do you have some suggestions that could get me started?
Thanks
-John
.
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