Navitron Renewable Energy and Sustainability Forum

Energy/Electricity Storage and Use/Grid Connection => Off-Grid, Batteries & Inverters => Topic started by: heatherhopper on June 17, 2015, 11:15:05 AM

Title: What PLC?
Post by: heatherhopper on June 17, 2015, 11:15:05 AM
Can anyone point me in the direction of a small industrial grade PLC that is cheapish, robust, of good quality and as near idiot friendly as possible? This would initially be for a single input proportional to Sunny Island frequency modulation (dare I mention that!), and three proportional outputs to SSR's all probably 0-10v or 4-20ma. Possible future expansion to include some Temperature inputs.
I realise lots of people would go down the Arduino route for this sort of thing but for me life is a bit too short for that - looked into it and everything is still gobbledigook to me. I really want a purpose made, off-the shelf product and think I could get away with simple ladder programming (of which I have some very basic expereince) for what will be a one-of job rather than a hobby.
I have been looking at Crouzet PLCs and the like thus far.

Title: Re: What PLC?
Post by: Tinbum on June 17, 2015, 11:37:03 AM
I've not had much experience with PLC's but have come across these in generators.


To be in that environment they must be built well.

Title: Re: What PLC?
Post by: roys on June 17, 2015, 12:21:29 PM
Used Omron and Mitsubishi Melsec F series I think, both of them years ago, but both of them fairly simple to use.  Ladder logic is the way I do it as well.

Title: Re: What PLC?
Post by: skyewright on June 17, 2015, 04:24:33 PM
Do I recall that you're in the Peak District (I could easily be wrong)?
If you are anywhere near the Hope Valley, TMS Europe are based between Bradwell & Brough. There have the sort of thing I think you need, loads of experience & expertise in process control, and are a nice bunch of people. Among other things they stock OMRON units (already mentioned by others).

Also available via the Internet, but sometimes it's nice to know a firm just down the road.  :)

Disclosure: I worked for them about 25 years ago (but not in process control [or sales!]) and am still in occasional contact (socially) with a guy who still works there. I'll be wanting some SSRs myself shortly and I was pleasantly surprised when they appeared at the top when I did a web search.

Title: Re: What PLC?
Post by: nowty on June 17, 2015, 10:03:23 PM
Hi Heatherhopper,

Sounds like you want to do what I wanted and thatís to utilise excess power from my Sunny Island offgrid system, especially when your batteries are full ?

There is a frequency controlled switch you can buy but itís a simple on / off affair so I suspect like me you have discounted that.

I use an Immersun type device to proportionally dump excess power to heat water with no risk of taking any power out of my batteries. I simply pretend that the Sunny Island is the grid with my Sunny Boy feeding it.
I use the multi function relay in the Sunny Island to switch on an adjustable time delay relay when the battery SOC is 90%+. Then the time delay relay allows a further amount of absorption charging before it switches on the Immersun type device.

The Immersun type device then ensures there is no import from the Sunny Island (i.e. export from the batteries) but dumps up to 3kw from the Sunny Boy into an immersion heater. It fools the Sunny Island into thinking there is no excess power and therefore the Sunny Island stays at 50Hz so the Sunny Boy does not throttle back with the immersun type device using near all the available excess power.

Pics below show my increase in yield using this between last year and this, its basically doubled it (note, the pics have different scales).

April 2014 - Total Yield 246 kWh's
( (

April 2015 - Total Yield 538 kWh's
( (

Title: Re: What PLC?
Post by: heatherhopper on June 18, 2015, 12:07:13 AM
Thanks for the responses.

I've added the mentioned units/makers to my possible list.

skyewright - I'm probably nearer you than the Peak District but have had a look at TMS. They seem a likely candidate to deal with (and stock Eurotherms which I am, or rather was, familiar with) - I do prefer to source from real people who are well experienced in the particular field. I will probably give them a call.

Nowty - I was very interested in your use of the Immersun when you first posted it - good to see it works.
Unfortunately I don't think I can go down that route - I need to be able to divert excess at all SOC levels. I have been using frequency protection relays to control a series of diverts for several years now and this works very well but as you say it is just crude on/off and not proportional so not ideal. I have, though, never had a GTI back off - which is the main aim for obvious reasons.
The frequency shift is the perfect trigger for me - it is very responsive and controlled (as much so as traditional DC voltage based divert systems from what I can see from recent viewing of some SI data sets). Using the frequency shift to control SSRs (burst fire I think) seems the logical route and hence the PLC requirement as the link which can also be utilised to expand the process logic loops to include various temperature/valve postion parameters.
All still in the thinking-about stage at the moment.

Title: Re: What PLC?
Post by: knighty on June 18, 2015, 12:25:36 AM
I think n Arduino might be better and easier than you think

once you get over the first hump of getting the add-ons you need, and getting it to do basic stuff like turn on and off an LED the other stuff you need is pretty easy

for instance... if you want to keep the frequency between 50 and 51hz

you can program in lots of potions like,
if frequency = 50.05 hz then do this
if frequency = 50.1 hz then do this

etc. etc.

or you could do
read frequency
then -50 from that number
then multiply answer by 100

so 50.23hz
becomes .23
and then 23

which gives you a percentage to run your dump loads, so 50.23 gives 23%, 50.56 gives 56% 51.00 gives 100%, etc. etc.

once you have that going, you can easily add in your valve controls etc,,
simple as, if this=than then power whatever on (or off)

(and these can be completely separate from the part of the program which runs the dump loads... even if they take information from each other)

but the biggest advantage is data recording... it's really really easy to get it to dump recorded valves into a file every X seconds...

which you can pull out and put into excel, to make some pretty graphs.... which also help you understand what's going on and how ell the system is working / if it needs any tweaks


Title: Re: What PLC?
Post by: heatherhopper on June 18, 2015, 11:13:37 PM
OK knighty you have me intrigued - I've ordered some Arduino stuff and if I can get past the lighting of the LED I might give it a try. If not I'm sure I'll learn a bit anyway. Certainly cheap enough for a bit of fiddling.

Title: Re: What PLC?
Post by: knighty on June 18, 2015, 11:25:58 PM
when you get it, it'll take you a little while to figure out how to connect to it, then do upload a program

but it's surprising how easy everything is....

to turn on an led is as simple as

(pin,13) on

(or something like that... I can't quite remember!)

Title: Re: What PLC?
Post by: Tinbum on June 19, 2015, 08:28:00 AM
I knew nothing about Arduino but you soon get the hang of it and it so adaptable.

Its also very cheap in comparison with other things.

Title: Re: What PLC?
Post by: Paulh_Boats on September 07, 2015, 08:22:05 PM
A very cheap and plentiful resource for learning program logic is Javascript tutorials.

There are millions all over the web. Choose the ones where you type in and see the results immediately.

You can't switch on LEDs but you can pop up a message saying "led 4 on" and later find ways of drawing white and red X letters for a string of leds.

You will learn transferable skills that lead onto hardware based program logic.