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PLC controls
By FuddyDuddy, Section Diaries Posted on Sat Jul 5th, 2008 at 07:29:39 PM MST
Control

I've noticed a lot of different control systems listed on the site, but I've never seen anyone that has used a PLC (programmable logic controller) system.
I'm a retired industrial controls technician (NOT an engineer) and have a small PLC which controls the heating and cooling in my home. I have a 6' x 9' "solar" room on the south side of the house and normally can see a 50 degrees (F) difference in that area from the outside temperature, When the temperature comes up in that area at least 20 degrees above the basement, the PLC turns on a set of small (surplus) fans and draws that heat into the basement for heat. I can get anywhere from 6 to 8 hours on a sunny, but cold, day. This really helps the heating bill.
During the summer I shift a pipe cap inside the solar area to the inside from the outside and simply "tell" the system to cool the house. The fans then run when it's cooler outside, bringing cool air into the basement. From that I usually get from 8 - 12 hours of run time. This offsets my cooling bill by up to 30%. The fan in my air handler is programmed to run "fan only" when the temperature is either over or under by a preselected difference before running the heat pump. The one connected electric heating element only runs if the outside temperature is below the "efficiency" level of the heat pump.
This system has saved us quite a bit on our heating/cooling bills over the seven years it's been running, but I'm still always looking at ways to improve it's efficiency.
I am teaching one young fellow how this is done so he can do something similar to his home, but I've not seen anything on this site that indicates others might be interested in something similar.
I have a "test" project that I'm working on and it monitors both PV cell inputs and battery voltage. I can use this to control when the batteries need a charge and when the excess goes to a dump load.
I'm also playing with the idea of using this on a small wind generator and have gotten much good information from the site in building them.
Should be interesting.....
Anyone interested in something like this ??
Contact: long.shanks@comcast.net
FuddyDuddy

PLC controls | 9 comments (9 topical, 0 editorial)

Re: PLC controls (3.00 / 0) (#1)
by ve6aym on Sat Jul 5th, 2008 at 11:04:58 PM MST
(User Info)

Hi,
I really think there are a lot of us out here that are more than interested in plc control. I have all or most of the modules to program them but just cant write programming language worth a hoot.. I have the technical electronic know how but just cant get my head around the thinking needed to come up with a suitable program..
I, for one would appreciate any wisdom you can impart on getting me going..I am sure I speak for a lot out there..

Re: PLC controls (3.00 / 0) (#6)
by FuddyDuddy (long.shanks@comcast.net) on Mon Jul 7th, 2008 at 11:05:46 PM MST
(User Info)

Boy, that depends on what you want to do..... You will need some analog inputs. Read down and look for my post on the FX2N-8AD. Warning, new these units run around $690. I got two on eBay for about $75 apiece, but it took time.
FuddyDuddy

[ Parent ]

Re: PLC controls (3.00 / 0) (#2)
by bob g on Sun Jul 6th, 2008 at 02:23:04 AM MST
(User Info)

Fuddy:

i wondered how long it would be before someone bubbled to the top :)

a friend of mine got me started with the parallax bs2 stamp about 2 years ago,
and it didn't take long for me to see how useful those things can be.

then i got to studying the plc's most particularly the dl305 series (koyo/automation direct, etc) but found the ladder logic a bit more confusing for me. maybe because the programming is closed source and sometimes expensive.

anyway, i bought a pile of dl305 stuff, and began to look at the backplane, the processor module, and the I/O modules,, tried to get the schematics but no luck.

so it took a while but i reverse engineered the 16 port I/O module to see how it worked or rather how i could take control of it.

the upside is melding of the two technologies, one backplane with 5 bs2 processors all running at the same time, with a master processor keeping the peace.

anyway i digress :)

suffice it to say the project quickly became very interesting but certainly not in keeping with the KISS principles, so i tabled it for a bit.

now with rising energy costs, i am thinking it is time to pull it back out and start back in where i left off.

what plc platform do you work with or prefer?

bob g

Re: PLC controls (3.00 / 0) (#5)
by FuddyDuddy (long.shanks@comcast.net) on Mon Jul 7th, 2008 at 11:03:05 PM MST
(User Info)

I've worked with Modicon, A/B, TI, ISSC, GE, KOYO, Mitsubishi, and Keyence. Now and for about the last five years I've worked with Mitsubishi (FX1N, FX2N, A, A1S and Q series). The thing I like about the FX series is the FX2N-8AD, which is a 8 input analog unit. It can be programmed for +/-10vdc, 4-20madc, type T, J & K thermoucouples.
The TC's will give you an accuracy of 0.1 degrees and can be set foe either F or C readout. Each of the eight channels is seperatally programmed... Really neat and fast. The FX2N plc's can do 8000 steps and even at about 3500, with math and compares will still scan at about 20-25ms.
As it's been pointed out, the programming language is the spendy part. There is a MELSEC package that I've seen on eBay, but keep in mind... It's a DOS based package, not Windows.
I also like the KOYO series. They are nice little units. KOYO was the original manufacturer of the GE Series one until GE decided they could do better... Hah !!
The worst of the bunch I've worked with is the Keyence. Their logic will accept (and run) a coil right in the middle of a logic string. Makes the program hard to follow and really does some wierd stuff.
The main thing I've found for a "home" project is: Get those eight analog inputs 'cause you'll need them for temperatures, battery and PV cell voltages, mill output, etc.
FuddyDuddy
Carlton, Oregon 97111 Deep into the temperate zone, very mild here.

[ Parent ]

Re: PLC controls (3.00 / 0) (#3)
by domwild (domwild at hotmail dot com) on Sun Jul 6th, 2008 at 04:07:25 AM MST
(User Info)

Friends,

One site working with Picaxe controllers for wind mills, which are easily programmed via a BASIC-type language, is www.thebackshed.com. However, it is realized that a PLC has much more processing power than the Picaxe.

The beauty of the Picaxe is the ability to program the chip via a PC, so it does not need a separate burner. And there is no need to learn Assembler.

.

dom There is one thing money cannot buy: POVERTY!

Re: PLC controls (3.00 / 0) (#4)
by welldog on Sun Jul 6th, 2008 at 08:09:45 AM MST
(User Info)

I have some experience playing with PLC's and have parts laying around for future projects. So, Yes any discussion on PLCs is interesting. The software for programming seems to be one of the biggest costs. Ebay is a great place to get software and a PLC for cheap.
I do have some experience with Automation Direct and Koyo PLCs. They are very robust and for the cost, well worth the money.
Sounds like way to much fun.

Welldog

Re: PLC controls (3.00 / 0) (#7)
by FuddyDuddy (long.shanks@comcast.net) on Mon Jul 7th, 2008 at 11:12:43 PM MST
(User Info)

The system running my house is all Mitsubishi.
The PLC is a FX1N-40MT with a FX2N-8EYT and a FX2N-8AD. The 40MT is the main PLC and has 24 in/16 out (all 24vdc). The 8EYT is a 8 point output module (relay) so it can handle what little non-24vdc stuff I have. The 8AD is my analog input module and monitors temperatures, voltages and currents.

The system that is on my test bench now is a FX2N-48MR and is a 24 in/24 out. All inputs are 24vdc, the outputs are relays and will handle 2 amps. There are two 8AD's connected for 16 analog inputs and I have a FX2N-4DA connected also. This is a 4 point analog output. I'm using that to control a VFD with a 1hp motor on it. The VFD is a 5hp unit, so I feed it with a 120/480v 1kva transformer (single phase) and can get 480v 3 phase out.

FuddyDuddy

[ Parent ]

Re: PLC controls (3.00 / 0) (#8)
by pvale (pvale at pvale dot com) on Tue Jul 8th, 2008 at 09:05:18 PM MST
(User Info)

I've played around with the basic stamp a lot, in fact I'm using one right now in a "fox" transmitter I'm going to hide at our Hamfest July 20th. If you look around on Parallax's site under controls/industrial, you'll see something called the Stamp PLC. Last I looked, it was around $200, but it makes the Stamp do 24V input and output, and has space for a A/D convertor to get some analog input.

I have bunches of small SSR's that handle up to 240V and 10A. I've fed those things directly from a Stamp pin before to control 120V stuff. I've also got some 60V 5A DC output SSR's but they seem to have a rather high on resistance and need to control fairly large DC signals, too much loss with very low volts stuff. They may be alright at 24 or 48 volts, but seem not to work at 12V very well.

Anyone who wants to check out our ham radio club, I'm webmaster and our webiste is;

http:\www.zerobeaters.org

Re: PLC controls (3.00 / 0) (#9)
by FuddyDuddy (long.shanks@comcast.net) on Wed Sep 17th, 2008 at 10:41:59 PM MST
(User Info)

What has happened to "whole house control" ??
I don't really see anything on this site that really talks about that, except with the possibility of using LED lights, etc...
I have had, for years, a PLC (Programmable Logic Controller) that controls my heating and cooling system which includes an air handler and a heat pump. I also have a 6' x 9' by 8' high solar area for heat absorption. That area has supplied our home with about 30% of our heating requirements over the years it's been in service, which is about seven years now.
I see a lot of articles about bits and pieces, but not anything major. Where have the thinkers gone ??
I have, historically, gotten about a 50 degree F rise above ambient for the solar area system, The current re-do is with a solar "box" on the south side with which I'm hoping to get about a 75 degree F rise. I'm including a 1/3hp, 480vac, 60hz motor on a VFD to get even more use from the area.
I'm retired and more than willing to share my knowledge with others wanting to do something similar.
Are there any of you out there ? The PLC's I'm currently using are Mitsubishi, bought on eBay for a very nominal price. They are higher now, but still a good deal.
My system is a FX1N-40MT, with a FX2N-8AD analog input module and a FX1N-8EYT output module. I plan to add a FX0N-3A module for the variable speed drive. That code has been tested and works fine. The VFD is a Mitsubishi E540, fed with a 120/480vac transformer, hooked to a Baldor 1/3Hp motor rated 480vac/60Hz/3 phase.

PLC controls | 9 comments (9 topical, 0 editorial)

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