A few KNX questions....

soldsold

Hi,

Some KNX questions I'd like to find answers to (hopefully someone can help) are:

1. Can I use my currently installed rectangular back boxes?

2. Can I run it over Cat5 - I have been very careful not to run the Cat5 UTP near and mains current wires

3. Would I be mad to try to install and program myself? I can borrow a copy of ETS3.0f so wont have that cost. Im generally handy with PC's doing upgrades etc and have an engineering background but dont have an electrical/ PLC background.

4. If I want to install myself would it be possible to get some advice ie paying someone to give me a day's consultancy to get me started and/ or troubleshooting if there are issues?

5. Can KNX work with LED striplights and LED mains voltage downlighters (eg 3w downlighters)?

6. Is it really worth the hassle of looking for KNX certified equipment, when my local hardware store carries the usual range of thermostats, central heating pumps, etc?

7. Anyone out there who thinks KNX is a bad idea? For one there doesnt seem to be any english language forums which is where I normally start if I run into PC issues. I know that KNX is big in mainland Europe but not over here.

Maybe with FAS now running KNX certification courses, A KNX forum on boards.ie would be possible

Thanks!

Steve

maxamillius

you cant use standard back boxes,you need the circular ones specified for knx,the switches etc are to big for standard back boxes

knx is run over a 2 pair bus cable not cat 5

it will run all lighting so led's are fine to use

i personally think its a great system as it cuts the labour time hugely,but it is also very expensive,actuators are in around 400 euro and a switch will set you back 100 euro!

you would really want to know what your doing to programme it,its no hugely difficult but you still need to know what your doing!

knx

Hi Soldsold,

I have come across a good few people asking similar questions. So to answer yours one by one.

1. The majority of knx bus couplers and plates are european standard fittings and are designed for the european standard boxes which are smaller and circular. The fittings will just about fit our uk standard 1 gang boxes but they have to be perfectly flush with your finished wall. There are adapter plates available to do the job but only for 1 gang boxes.

2. It will run over cat5 but because the cross sectional area of the cat 5 is smaller than the proper bus cable you need to be sure you have a decent connection at each point. Also it is very easy to nip the cat5 when stripping with a snips and this will weaken the cable and it could snap when pushing the bus coupler back into the box.

3. The cost of doing the course and purchasing your own copy of ETS could quite easily be justified by the saving you would make on the equipment after your qualified. If you are a certified integrator you can go to the trade only suppliers and avail of trade rates. Pm me for details on some of these.

4. Entirely possible.

5. No problems with this whatsoever.

6. It's no hassle sourcing equipment. I buy all of mine from online suppliers but you have to know what your looking for and select the right device for the job. Lots of manufacturers make lots of different acutators that have lots of different features and you have to know what you are looking for. Also because of the fact that the majority of manufacturers are european there are a lot of dodgy translations. Something to bear in mind.

7.There's plenty of support available. You just have to know where to look for it. You won't find much trawling through the internet with the aid of google and many suppliers just won't talk to you unless you are certified.

Hope this helps. Pm for any other advice..

maxamillius

hi knx,just as a matter of interest do you work for yourself or do you work for a knx installer,i recently completed the course,just awaiting the advanced course now,i think i took to it pretty quickly and just wonderin were there any jobs in it,thanks

maxer

Hi,
i am an advanced KNX Certified Engineer and have designed and installed Ireland's largest commercial and residential KNX Projects over the last 7 years.

You can use cat 5, but you have to be particularly careful when the cable is run inside a distribution board. The EMC can affect the transmission of the KNX telegrams. The correct KNX bus cable is shielded, but if to much of the shield is removed, it can have the same affect, especially inside the top of a distribution board where all of the existing power cables are normally terminated. This is why we normally keep the KNX equipment and termination at the bottom.

As for the cost, If you are still interested, PM me as we buy huge amounts of KNX kit, we have some secondhand stuff in stock and can offer good discounts. I would program a complex house with lighting and heating in a matter of hours, so we would throw in that for free. We also have the adaptor plates in stock for the Irish back-boxes.

Also there are now some pretty nice open-ware graphical software interfaces like openremote that you can engineer after and we have a lot of AV interfaces to allow switching off of TVs etc with the KNX presence detectors, or controlling of volume etc from the KNX switches which can really add value to the installation.

soldsold

Thanks for the replies, I've been busy building so am hoping to decide on knx options within the next week or so, will send out a few pm's in the next day or so to see what the options are.

Thanks again,

steve

liveandnetural

hi guys would anyone like to explain a bit more about knx for us that don't anything about it maybe theres a good website??

we learn a little every day

Umiq88

Probably a little off topic but still relevant

What are the benifits of using a KNX system over a standard PLC solution i.e. Siemens, AB etc. With work I encounter and am involved in designing a lot of automated equipment. If a PLC was put into a house you could use 24V digital signals for most of the control which would cut down on the cost of expensive back boxes and KNX sensors and you could use traditional switches. It can be tailored to nearly any piece of equipment which means you don't have to buy expensive KNX sensors.

I understand you wouldn't have the benifits of a bus system but in a house for a once of wire its's not much of a concern and you also wont have the added problem of emc interferance as 24V digital signals are quite roboust.

knx

@ liveandneutral

http://www.knx.org/knx-standard/introduction/

@ psittacosis

Firstly my experience of PLCs is limited to some minor programming as an apprentice in FAS 18 years ago so I would imagine things have moved on since then.

I suppose the main advantage of knx is the fact that it is a protocol as opposed to a brandname and many different manufacturers make devices that conform to the standard. There are devices available to control pretty much any kind of electrical load and also sensors to control that load based on various environmental conditions. It was primarily used in commercial buildings but has been finding its way into the domestic market for the last number of years. The technology itself is 20 years old now.

So lets take a domestic situation where scene setting and dimming is required, control over ufh with multiple heat sources and say electric shutters or blinds need to be controlled. There is a knx actuator available for all of these tasks and all can be controlled from one push button or room controller. So there is no interfacing with other equipment and obviously no need for any other control systems. Sensors can also be programmed to have different functions based on time of day or external temp or lux levels. Scenes can be programmed to incorporate all of the elements, so for instance a presence detector inside your front door can release several different scenes based on time and brightness automatically. During the day you walk in and the heating is brought up to comfort level in the living areas and required services are switched on. At night it will do the same but will also lower the blinds and turn on a predefined welcome lighting scene. On the heating side of things, some basic logic is usually built into the actuators allowing control over multiple heat sources if necessary. Load monitoring and operating hour counters can also be built in.

Another advantage is the fact that there is no central controller. Every device has its own memory and any programming associated with that device is stored within. So in the unlikely event of one particular device failing the rest of the system functions regardless. The memory is flash memory so the bus power can be switched off for long periods of time with no consequences. You can even paramterise the behaviour of your devices in this event.

Anyway I'm sure I've said enough for now to spark some more debate...

Carlow52

knx wrote: »

@ liveandneutral

http://www.knx.org/knx-standard/introduction/

@ psittacosis

Firstly my experience of PLCs is limited to some minor programming as an apprentice in FAS 18 years ago so I would imagine things have moved on since then.

I suppose the main advantage of knx is the fact that it is a protocol as opposed to a brandname and many different manufacturers make devices that conform to the standard. There are devices available to control pretty much any kind of electrical load and also sensors to control that load based on various environmental conditions. It was primarily used in commercial buildings but has been finding its way into the domestic market for the last number of years. The technology itself is 20 years old now.

So lets take a domestic situation where scene setting and dimming is required, control over ufh with multiple heat sources and say electric shutters or blinds need to be controlled. There is a knx actuator available for all of these tasks and all can be controlled from one push button or room controller. So there is no interfacing with other equipment and obviously no need for any other control systems. Sensors can also be programmed to have different functions based on time of day or external temp or lux levels. Scenes can be programmed to incorporate all of the elements, so for instance a presence detector inside your front door can release several different scenes based on time and brightness automatically. During the day you walk in and the heating is brought up to comfort level in the living areas and required services are switched on. At night it will do the same but will also lower the blinds and turn on a predefined welcome lighting scene. On the heating side of things, some basic logic is usually built into the actuators allowing control over multiple heat sources if necessary. Load monitoring and operating hour counters can also be built in.

Another advantage is the fact that there is no central controller. Every device has its own memory and any programming associated with that device is stored within. So in the unlikely event of one particular device failing the rest of the system functions regardless. The memory is flash memory so the bus power can be switched off for long periods of time with no consequences. You can even paramterise the behaviour of your devices in this event.

Anyway I'm sure I've said enough for now to spark some more debate...

Sounds like SWMBO without the audio to me:D

knx

Carlow52 wrote: »

Sounds like SWMBO without the audio to me:D

Correct..

LynchKNX

Of course you can use standard back boxes I have used them all over Ireland with no Probs

The Sponge

Can somebody please explain to me why KNX is so expensive???

Lets take an average "640ma power supply" for example: €250

Surely there is nothing too sophisticated about this device. I would have thought that it just consisted of a transformer and a pcb board regulating the output.

An smart phone / tablet / laptop is less than twice the value and look what they can do!

If the price of all typical KNX devices were to be reduced by about 70% I image the industry would pick up, but at the moment to me it really does not make sense!

2011

The Sponge wrote: »

Surely there is nothing too sophisticated about this device. I would have thought that it just consisted of a transformer and a pcb board regulating the output.

I have never used KNX so can not claim to have any expertise on the subject. Following a quick Google I agree it does seem to be quite expensive.

However devices may not always be as they first seem. For example, take the Power Supply Unit, (PSU) This is likely to be a switched mode power supply (not a transformer) that can supply 29VDC output when the input is anything between 120 and 250VAC. It will provide a far "cleaner" supply than your average PSU within much tighter tolerances required for sophisticated components. It also has short circuit and overload protection. This is where the extra money is going.

LeBash

250 is a little expensive. Check around local and you'll pick it up little cheaper.

As far as I remember the PSU superimposes an ac waveform on a dc current. Also the reply above is correct, its not just a wirewound trafo.

Anyway, its a very reliable system, not very labour intensive and some features such as modulation of heating etc are great.

Also, you can use square boxes, not sure where that came from but I don't understand why that would be an issue. Circular boxes are about 80 cent for a quick install or 40 cent for standard and all you need is a 67mm holesaw.

2011

LeBash wrote: »

As far as I remember the PSU superimposes an ac waveform on a dc current.

Interesting, what is the purpose of this waveform/signal?

LeBash

2011 wrote: »

Interesting, what is the purpose of this waveform/signal?

I'm sure there is a reason behind it but I don't know to be honest. I was just making the point that its not a basic PSU and probably part of the reason behind the price.

Dazman1

Hi

Is the PX24500 Controller compatible with DMX512.
Has anyone use this before because one of my controllers have burnt out where the patch lead is.Any one help please.

maxer

Yes the PX24500 Controlleris a DMX driver to control the local luminaire led. and will work in any dmx lighting system.
The patch side is the DMX bus connection and should already be protected as its voltage comes from the main DMX controller (~12V) which will have bus protection in it.
I would check the connections to see if there possibly is some short and also check that the driver is not getting too hot and is ventilated.

DMX is a basic bus system (Rs485), typically used for stage/theater type lighting and commonly found in LED color change lighting applications.
The 512 refers to the amount of channels/devices you can have on a single DMX bus. For example if you have a RGB driver like the PX24500, this will use up 3 channels (one for each color). Each driver will have DMX addresses that have to be set.

You can mix and match different DMX devices together on a network and they have to be connected in a daisy-chain using cat 5 or a similar bus cable. At the start of the network you will have the actual controller and this tells all the drivers what to do as they are all addressed. Also there should always be a 120 ohm termination resistor at the first and last device on the network.

Dazman1

Could anyone recommend a decoder to use with my DMX 512