Infrastructure, cabling & design

@lessmann and @Raks So far I had a quick look at both these examples and what caught my eye was the UniPi Axon L205.

It has an impressive amount of onboard I/O (although a little light on for analog I feel?).

Digital inputs 36
Digital outputs 4
Relay outputs 28
Analog inputs 1
Analog outputs 1
RS485 serial interface 2
RS232 serial interface 1
1-Wire bus 1
Ethernet 1

Total of 70 I/O PLUS they have a range of expansions available

The software looks to be Function Block Diagram type

It also is compatible with Node-Red

And is compatible with other Open Source software but it does not list HA at this time.

All up this device looks to be fairly useful for the price of 619,00 €

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@lessmann and @Raks by comparison the Loxone Miniserver has the following onboard inputs and outputs:

LAN Connection
8x Digital Inputs 8VDC – 24VDC
4x Analog 0-10V Inputs
4x Analog 0-10V Outputs (max. 20mA)
KNX/EIB Connection
Power Supply 24VDC
Loxone Link
8x Digital Outputs 250V/5A

Total of 24 I/O
NOTE: No relay outputs onboard?

Total cost £ 485.65

They do mention :
The Miniserver lays the foundation for every installation and comes with our free software and mobile apps for convenient configuration and control.

The Miniserver can control:

Energy monitoring and management
and much more

For instance they have Dimmer Modules and Relay Modules, etc

They offer free software

They don’t seem to have any mention of compatibility to open source or HA etc but I may have missed that?

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Thanks Stephen

The Unipi definitely tops the list of bang for buck and its open source, my only worry at this stage is how to integrate it into HA.
Jan Teunis has done some work on converting the Unipi Evoke data to mqtt which looks promising and you have done some good work on integrating the xLogic Soft with the HA modbus hub. Thanks for sharing your project!

I am much better at copying someone else’s code than I am at writing my own so it’s reassuring that some of my HA pals have had a go at this. Both of these option look promising and I know Evoke is supported by Unipi but there is no mention of xLogic Soft. I really have to just get one of the PLC’s and start playing around with it so I can get familiar with it because once we start building I’ll have a million other things to figure out. The only problem is choosing which one.

As I’m an absolute PLC newbie I was hoping to pick your brain on a couple things…

I would need more I/O and relays than any single PLC offers so I was hoping to “daisy chain” two together to increase this. I know Unipi has the extension modules but they don’t offer as many AI/AO as the PLC’s do, or even Relays for that matter. Would this work or would I end up having to access the devices separately? Also what if I want an input on one device to trigger an output on another?

Secondly, RGB(red, green,blue) and SW(simple white) dimming. I assume this is where I need those AO’s 0-10v to manage a dimmer module like this Vellermann for RGB or this Anigmo for SW.

The Vellerman instruction manual has an easy to understand wiring diagram.

Regarding the Loxone, I think the mentioned DO’s in their documentation actually refers to relays. If you look at the pictures of the inside of the miniserver there are clearly 8 relays in there.

The Loxone systems biggest advantage is their “tree” topography. Instead of each device having to come back to the PLC, or miniserver in this case, there is a “tree” module which the devices can daisy chain onto. So instead of many data cables running to each different location you only have one running to the location and then they connect to each other, device to device. Great for installation of course, but you have to use one of their tree compatible devices and I worry about future proofing. What if I or the next owner doesn’t like Loxone and needs a star wired set up? But then the chances are that if you are going to rip it all out you will probably be doing a refurb and new wiring job anyway so maybe I’m over thinking this.

Also Loxone has some really nice “out of the box” devices. Their switch plates are excellent and light dimming seems to be really straight forward. Also there is a big enough forum community.

Maybe the solution is to split it up. Do the lights and switches with Loxone and all the blinds and heating etc with Unipi… There are so many options!


Conduit is great of course, but you can’t, for example, run mains power and ethernet (or other low voltage signalling) in the same conduit.

The other problem of course is that you’ll never know how you’ll use your house until you live in it. You don’t know if you’ll need a fan to circulate the hot air from the fire, so you mightn’t know that you need cabling for it. You don’t know when some new device will come out that needs to be placed somewhere you never thought of - a few years ago who thought we’d need somewhere to plug in all those Alexa things and smart speakers, not to mention motion, humidity and temp sensors all over the house.


It is a shame that home assistant isn’t in this list, given that domoticz and node red are there (among other OS projects)



From the UniPi Axon L205 website and in particular in regards “Modbus RTU protocol”

Communication interfaces

Axon controllers are by default provided with RS485 serial lines. This type of interface usually uses the Modbus RTU protocol and can be used to communicate with various devices such as Extension xS extension modules, energy meters, touchscreen HMI displays , controllers from other vendors, various sensors etc. A single bus can support dozens of devices while the bus’ length can reach up to several hundred meters.

Selected models also feature a single RS232 serial line. In the field of automation, this interface is usually used for communication with various converters, closed-in technologies or display devices such as HMI panels.

A single 1-Wire bus is also featured on selected models. This interface uses 2-3 conductors for collecting data from various 1-Wire sensors such as thermometers, humidity meters, light intensity sensors etc.). A single 1-Wire bus supports up to 15 devices, the overall length of the bus can reach up to 100 meters.

All Axon models also feature a single 1Gbit Ethernet port for network communication.

So from that I believe this device would be compatible with HA as it supports Modbus RTU. To check that it supports that over ethernet TCP though? It does not specifically state that?

It also says that the PLC supports 1-Wire bus which “should” mean that loads of (nice cheap!) 1-Wire sensors can interact directly with the PLC rather than be connected to wireless devices first like ESP’s, Wemos, Sonoff, etc. That sounds like it would be quite useful let me tell you!

The thing to check is how easy their software makes it to connect internal registers with HA.

xLogic Soft makes it quite easy as each register which can be communicated with has been clearly labelled with the necessary communication parameters required.

Same for any other platform you choose in the end…just ask yourself…does the device programming software make it easy for you to setup the HA connection you will be using quite often?

I’ll try to answer some other questions a little later ok.

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unipi has various software implementations, I looked at one of them Evok. It is free, although I couldn’t find a licence.

Anyway, point is it has an extensive rest api

It should therefore be possible to use a rest integration, or write a whole integration.

Lots of options.



With PLC’s I have been involved with that have been fitted with expansion modules the main PLC simply becomes a larger integrated device. Hence the program just has more I/O to command.

Expansions are all just allotted a slot on the machines bus (in most cases CanBus) but there are others.

So what I have managed to do with ELC series PLC’s is this:

To date I have tested the single CanBus extension up to 20m.

I have also tested inserting a first and second CanBus extension up to around 30m.

I see no reason why you ccould not have every expansion split with a CanBus extension up to 30m total length and most likely more.

And remember that the main PLC program (and importantly HA via modbus) can directly access every register on every expansion as its own integrated self.

NOTE: The cable is just standard Cat5 patch lead.

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That’s true @nickrout but in a good plan you would have several conduits for different wiring systems…just planning what you need is the key.

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@nickrout @wellsy you both right on spare-conduit in design stage. in my case i will move into a house and rewire it and then choose the right equipment and add the automation over the time. People can’t foresee all the future needs especially if you are not living there yet and a learner in that field and when the technology changing as well. But “spare-conduit” is better than nothing. There are other options like using “skirting” and “coving” as concealed trunking that you can access and run the cables later without much damage but all have some limitations.
Even I thought about putting one controller in each room above the each rooms door (inserting a box with recessed accessing panel and run the cables through the coving/skirting trunking as needed) but still have to consider the easy maintenance, cost, safety as well as the decorative look.
We can plan most of the cabling for the essential and critical devices in automation and hope there will be more advances and “no concerns” on wireless technology in coming years for the unplanned ones. :slight_smile:

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Not too sure why the CanBus is necessary, don’t the Ext’s just connect in series with the RS485 cable? Anyway I’ve had another look and it’s probably much of a muchness if I go for two PLC’s or one with three Ext’s.
Now I just have to decide between the Neuron Or Axon… not much in it costwise…

Extra conduit is a good idea but you’ll be surprised how difficult it is to pull cable through once everything is decorated. It’s frustratingly hard to get it round those corners so it really is better to pull through as much as you can before. Don’t expect that you’ll be able to do this later because it may not be possible.
In my current house which I finished building 3 years ago I was such a novice that I thought I could pull the Cat5 cable from room to room in a ring circuit just like the electricity. I only realised once it was all in that this was totally wrong and even though there was additional conduit, I only managed to get extra cable through maybe half of the boxes. Luckily I managed to fix the problem by installing 5port switches at each location and extending the network that way but it’s not pretty.

I recommend where you have cabinets or cupboards to pull a few extra data cables to your controller room. These are convenient places to put extra sensors or additional switches if you want and possible new future devices.

Regarding a controller for each room. I think having everything in one location has it’s advantages. It will be much cheaper for a start.


I did notice the Evok software and the ability to use rest api’s, although I have no experience with rest api’s at this stage. I’ll look into it. Also @Teunis has done some work to convert the commands into mqtt which looks like something I’ll be very interested in once I’m at this stage.

I was kinda hoping I could just use the HA built in modbus integration…but I suspect that might not be as simple as I had hoped

@lessmann Yes you are right on their knowledgebase it is clearly stated “Extension modules are communicating with the PLC over the RS485 serial line and albeit they are designed primarily for the use with Neuron controllers, they can be used in combination with any PLC supporting the RS485 serial line and Modbus protocol.” I must confess I had only browsed specs and costs.

That then makes the extensions able to be mounted at remote locations from the PLC.

I think if you are at the point of choosing between these…

Then you probably should be looking deeper into the software and installing it on your computer to see if you are comfortable with using that for now.

@lessmann ideally conduits would be arranged to allow a vertical straight pull from a roof space to a box in the wall or a cupboard or horizontally from room to room in wall…again from box to box. Its a bad idea pulling Cat5 around bends anywhere. Straight runs with as little tension as possible during pulling in and 200-300mm coils at direction changes is best practice.

Do you have any dimming light circuits in your set up?
I’m particularly curious about possibly using these Faradite switches which are ideally for Loxone and emailing the supplier they confirm to have only tested these on the Loxone miniserver but they are essentially just 5 DI’s. I haven’t really found a nice looking AI dimmer so was wandering if it’s possible to manage the logic at PLC level for these.
Apparently if you hold them down they keep pulsing and I was wondering can I set it that for every DI pulse the AO is increased and another button does the dimming with the same logic?
I know this is quite a specific query but dimming seems to be the most confusing for me at this stage so would be grateful to hear how you have managed it.

@lessmann Sorry no I have not had too much experience with anything but Dynalite Dimmers (Large scale buiding lighting systems via BMS System). Nothing on a personal level.

I’ll have a look and see what I can find though.

UPDATE: Hmm…not too much of a technical nature around that I can find? Did you find a manual or datasheet etc? I see someone asked about Loxone compatibility back in February.

For many applications you are going to need high inrush capable relays and I am not convinced of the quality of the UniPi xS** I/O modules’ relays.
The datasheet ( gives little information about the relays used (“Switchable Current 5A”) and has errors too (“Short time overvoltage 5A” ?!). A reputable manufacturer would list the relays’ capabilites depending on different load scenarios (cos phi, inrush capabilty…). If you want to know what I mean take a look at page 4 of this datasheet (

I never liked the idea of having multiple relays built into a device. Therefore I went for a bunch of Modbus RTU (over RS485) capable I/O modules I’ve designed and built myself and external high inrush relays (for example TE Connectivity RT33L024 + din rail socket like Finder 95.85.3). You can get the combination of relay + din rail socket for less than 8€ if you are lucky. The relays can be replaced easily by pulling them out of the socket and sticking a new one in whenever necessary.

Also, you can use whatever I/O device/arduino/plc/raspberry pi you like. If you want to change the I/O thing you can do so without having to change any of the dangerous AC wiring. This can be very useful if you are partnering with an electrician, which you may have to in some countries…

Just my 2 cents.



@mbs38 @lessmann @Raks Yes you are correct. PLC’s are for control system use only. For final operation of 240V field devices a correctly rated and most importantly replaceable relay should be used. If you always setup your system like this the inbuilt PLC relays will last as per the advice of the manufacturer…a lifetime in most cases.

My relay (and base) of choice for that is the Finder brand such as this:

This type of base is excellent as 240V is all on the top and the control is all below. Which is perfect for ensuring segregation of mixed voltages.

My choice of control voltage is always 24VDC so the relays have 24VDC coils. (The image above shows a 24VAC relay)

NOTE: For higher power devices like larger HVAC equipment Pumps etc, you may even be using this relay to switch another larger contactor.

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I find those a little clunky. They are this big because of the many contacts - which you won’t need for this application.

My base of choice is this Finder 95.85.3:

It only has the normally closed terminals on the same side as the coil terminals - which I had no application for anyway.

For Finder 95.85.3 you can get relays from multiple manufacturers.


@mbs38 Yes, nothing wrong with that base and it does use less space in your din rail.

In most cases I only use the double pole double throw (DPDT) ones…the photo I posted earlier was just the first and best photo I came across sorry.
Its the type of base which is most important for me really.

Finder is the best quality (by far) in relays and worth the extra cost…I have relays that had been in service over 5 years operating a few small pumps at least 525,000 times and they just started to fail a month or so ago requiring replacement. Happy with that!

PS: I bought a box of 10 off ebay for $120 for Finder General Purpose 2 Pole Relay…I was ecstatic with that because in the past I have paid $19 each.

Also the other thing with the base I use is occasionally I may use the second pole for switching a nuetral or for interlocking purposes so DPDT is often a necessity for my purposes.

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The 5A is a potential problem I guess, the arduino powered relays I’m currently using around my house are all 10A. Although I’m guilty of not paying too much attention to the electric values until something goes poof!

I was intending to use low voltage led’s throughout the house, 24v/12v. Would this make the Amperage less important?

Thank you for your input I find it very helpful but this certainly throws a spanner in the works for me, I was about to buy the PLC so I can get to grips with the software but I clearly need to do more research and hear about experiences like yours.

If going down the route of separate relays I would need a PLC with high DI & DO to power all those relays. Are there any you’d particularly recommend?

I have asked Unipi about the choices between a large and small PLC with less or more Extensions and their responce was that of course the separation aids in replacement and but apparently increases latency.


The Unipi relays claim to have a lifespan of 5 000 000 ( I’m assuming this refers to switches) then, on the assumption that a light is switched on/off 10 times a day then this relay would last 1300 years.