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BwiggleS
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| Posted: November 10 2009 at 11:52 | IP Logged
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Just wondering if anyone here has implemented a modbus serial communications link to a serial device. I am going to purchase one of these
http://www.temcocontrols.com/product.php?ProductID=101&Categ oryID=22&PHPSESSID=0a9bd779246eb6f2adf41e28bee031a0
And I could bash and smash my way through it but if anyone has worked on a modbus serial interface already it would save time and probably work better than what I would create.
My plan is to install some temperature sensors around the house and this IO board is a pretty cheap option instead of using the EZIO analog input (plus the EZIO boards have a lot of negative comments).
Thoughts or comments?
Thanks,
Brad.
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BeachBum
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| Posted: November 10 2009 at 12:11 | IP Logged
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Did you check this out?
http://www.power-home.com/forum/forum_posts.asp?TID=1401&KW= sensor
__________________
Pete - X10 Oldie
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BwiggleS
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| Posted: November 10 2009 at 16:45 | IP Logged
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I saw that post but what I am looking for is a generic interface for modbus. The modules I am looking at work with any analog sensor (temp, pressure, humidity, moisture, etc) and they also make analog output, discrete input and discrete output modules. I come from the industrial automation world and I prefer the end devices to be a little more robust (i.e. RTD and temp transmitter).
For the modbus interface I need to calculate the CRC which will probably be a pita. I was hoping someone else had tried using it.
Brad.
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hotcoffee76
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| Posted: December 04 2009 at 23:36 | IP Logged
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Hi,
I am planning a temperature sensor network and would be interested in hearing any progress you guys make. I have a large, old house and want to monitor the various rooms to identify and prioritize window replacements, radiator maintenance, etc. The house is new to me, and there are lots of things to work on so this information will be very helpful.
My main challenge is getting the various readings to my PC. Once there, I'm fine with writing whatever software I need to process, store, manage, the readings. I am looking at how to get readings received by Powerhome into whatever software I build, but that's another topic.
So, for the sensors, I can use a hybrid approach since I can combine the readings and analyze in my own tools.
I have cat5 running to almost every room, so that is an option to use, but I am not sure I want to tie in sensors at every termination. Plus, there are many other uses for this. My alarm and phone have already tied up 2 pairs, and I want to leave some options open. As for additional wires, its an old house and it is not easy to get wires to many places. So, I am interested in wireless solutions.
I have seen an example of an X10/Arduino solution to send X10 commands with temperature readings, so that is one thing to explore. This will cost more per unit, but I don't really need a sensor in each room all the time for my purposes. I can rotate them around until I buy/build enough for the whole house.
So, if you guys have any thoughts on alternatives, approaches, etc. I would like to hear them.
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BwiggleS
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| Posted: January 10 2010 at 10:58 | IP Logged
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I have been ultra busy, didn't see the new posts.
Modbus is an industrial serial protocol used extensively in the oil and gas industry for talking to devices. www.modbus.org
It is very well defined, does not have any command confirmation unless you build it into your code. There is an RS-232 and RS-485 versions, so with RS-485 you can have up to 255 devices on one pair of wires (with limitations on distance of course, but in a house probably never going to be an issue). RS-485 is a daisy chain protocol, so the wires have to go to a device, then to the next and so on. If you have a cat 5 then you will probably need 2 pairs to each device, then in your networking closet you will need to daisy chain them together. Also, you are not limited to the type of device, you can have 5 devices at one location, all different types and can use just the 2 pair to talk to them. I can do up a sketch if you like.
I have found quite a few reasonably priced RS-485 modbus I/O the problem for me is I have not had any time to play with the PH scripting and really don't know much about it. Plus for windows apps the only thing I have done is played with VB6 a little. This side of it will be a challenge for me.
Keep in mind X10 can be flaky, insteon may be better, but these are still power wiring or wireless devices. To have them work over cat5 will require some kind of 1-wire or RS-485 solution.
Brad.
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PowerHome Messageboard : PowerHome Programming
Topic: Anyone used Modbus?
