Screw terminals vs plug-in on key modules

Hi All,


I upgraded one of my 5034Ns to a Neo-8 last week and whilst in the process of swapping the wiring over must have made and broken the contact to the Neo several times... (No, I definitely didn't short circuit it at all.)

The end result was the bus became rather upset, the Toolkit couldn't open the network, and I needed to de-power the whole shebang before I could talk to it again and program my new Neo.

(Returning the 5034N didn't resolve the problem, proving my new Neo was OK, rebooting the PC didn't help, and after I'd de/re-powered the bus it came up 100% straight away).


The thought that occurred to me at that point was why is Clipsal still putting screw terminals on the rear of input units?

I have a Pro dimmer and a 2-ch relay which both use a plug-on "green thingy" which would be ideal for the rear of input units, and would greatly speed the upgrade of key units like I was undertaking.

It has screw terminals for us to daisy-chain plenty of pink Cat5, and the plug-in nature of that terminal block would have to speed pre-cabling/installations and maintenance.

Another bonus of moving to these green things is if you're replacing units in the field like I was, those green blocks would also permit you to change a unit out without disturbing (unscrewing / re-screwing) the existing bus wiring.

And they probably fit the same 5.08mm PCB spacing!


(Disclosure: I have *no* interest in the manufacture or sale of green terminal block thingies).




Greig.

 

One of the often debated topics here at CIS is terminal blocks. Some products use RJ's, some use plug-in connectors and others use screw terminals. Just about every connector type possible has been considered, with cost usually being a big deciding factor as well as creating uniformity across different product families.

On the whole I'm very suprised that a series of intermittent connections made your network not work properly as C-Bus is highly tolerant of this sort of thing. I suspect that the causes could have been multiple units trying to generate the clock or a power supply somewhere that went into a funny mode. If it's an older installation and you've got 5100PS power supplies there then they are the likely culprit.

 

I also used to hate the screw terminals, but have subsequently found that they offer the most reliable method of connection for the switches.

The problem is that the switch needs to be crammed into a wall cavity, and in that process the cables inevitably move around. A plug-in like the green thing simply adds yet ANOTHER connection and possibility of fault.

Remember, you still have to screw down the cables into the green thing anyway. And I would HATE to have to terminate RJ45's at each switch position, because there's inevitably 2 or 3 looped Cat5's (how on earth could you cope with that with RJ45's?)

I'd say the screw terminals are best for size too - Green thing would add depth, and multiple RJ45's would increase the terminal footprint considerably.

 

Newman, you might have ID'd my problem - ours was a 1999 installation, so there's an old 5100PS here providing power supply redundancy in conjunction with the newer DIN rail dimmer. (I'm hoping to add another DIN dimmer in the next couple of months, so will retire the old PS at the same time).

As for connectors, I'm a big fan of consistency. I can see the benefits of using RJ45 sockets and short "patch leads" in a switchboard full of output units, but equally some kind of screw contact on the input units that are located throughout the installation.


JohnC, I agree with your concerns about connection depth. Clearly RJ45s are dead in the water in this domain, but I still contend there's a place for the green things. They would add little additional depth to an already fairly shallow mounting requirement.

(No-one will seriously suggest that any C-Bus installation is going to require more depth than a single gang switch wired with 1.5mm2 cable, let alone something more real-world like a 4-gang plate populated with 2 mechs & dimmers!)

Granted, I agree that there might be a risk of the green plug thingy becoming dislodged if/when the unit is stuffed in the wall (or cables are tugged nearby) but that could be overcome with a cable clamp arrangement or other locking means.

If there's a vote on it, I'll be campaigning for the green things!

(Remember, they're in use already on selected C-Bus devices!!)




Greig.

 

Which devices?

 

Hi Josh,

> Which devices?

The Pro series dimmer (DIMPR4 - 5A/ch) and the 2-channel relay (5102RVF) both use push-on connectors for the C-Bus.

OK, they're different styles, but the point is they're both using that same type of connecting technology.

There may be others in the C-Bus family with similar connectors on them which I haven't encountered. These two just happen to be two of the 18 devices sitting on my network here at home.



Greig.

 

LOL - I wasted hours hard-wiring single and 2 channel relays in our lighting showroom (we have maybe 50-60 in total). The balance of the system is DIN devices, and all these units are then chucked "loose" into suspended ceiling display boxes about 3.5m above the floor and hard-wired to various/numerous light fittings.

The hassle of course is that you have to make a separate Cat5 loom for the hard-wired units - I did it by hacking up 3-way RJ45 leads assemblies and then cutting one RJ45 off to wire it to the white 1/2 ch relays, a real PITA ! And all that stuff had to be done with the relays on the bench, then hauled up 3.5m for connection to the DIN devices and mains up in the ceiling box.

Then one day a connector on a relay FELL OFF ! That's when I dicovered the undocumented green plug thingy. Unfortunately, I had finished the installation - it was literally the last one I had to wire

What makes it sadder is that I was actively involved in the overall design of the 1/2 channel relays (admittedly back in the late 1990's) and I knew about, yet completely forgot about the green connector. Pita that CIS forgot to document some of these "features" in the instruction leaflets to remind me

JC

 

John,


Dare I ask for your thoughts on the AC connectors used on the 1 and 2-ch relays?? (Were you involved in that part of the design too??)




Greig.

 

Hi greig

I was mainly involved in the (white) casing design and original product brief to CIS Engineering on "what was required". It came about in (I think) about 1995 whilst I was working for Pierlite, and we had the need for a small, very cheap device to fit INSIDE a luminaire...

The original idea of Cbus was that instead of this crazy (current) system of centralised C-bus devices (in a switchboard) then have 1 load cable running out to every load in the building, Cbus was conceived to have the switching remotely (right next to the load).

In concept - the (unswitched) mains wiring looped around the building, tapped off to various load centres or luminaires which had almost "individual control" (small relays and dimmers). In "parallel" ran the Cat5 which also connected to all the switches. So, instead of requiring MORE cable, the original sales pitch for Cbus was to SAVE cable and labour to install all the switch wires.

There are a huge number of other advantages in this approach, especially in Commercial environments (which is what Cbus was originally designed for) - individual control of luminaires provided ultimate flexibility, using daylight and occupancy sensors to control the lights in each part of an office, and a master on/off at the front door. And since the Cbus device was AT the luminaire, there was no "load-side" cabling required. At the time, the cost savings in labour and cables would pay for the Cbus system!

Consider that the 2ch was probably only $80 trade at the time, and the 1ch maybe $50-60, so you could do a (large) project of individually controlled luminaires for (say) $30 per point, or $40 for individual dimming - and an added saving from the (zero) labour and no cabling for the switch wires. That was a bargain

You may not know that all the old (Cbus1) devices were mounted in small white surface mount enclosures (exactly like a 5104AM) and only had a small number of output channels. That was because there was no need for 8 or 12ch outputs, as that would require extra cabling out to all the (remote) loads.

The 1ch relay was the ultimate progression of that idea. It was designed to mount inside a fluorescent (office) luminaire. The cross-section and shape of the enclosure was exactly the same as a Clipsal electronic ballast that was manufactured at the time, and most other brands of ballasts too. The unit was designed to be as cheap as possible - no led's etc - stripped to the minimum, and all we needed was a relay and a way of doing 0-10V analogue dimming (of the electronic ballast).

The 2ch was designed to lower the cost even further when dimming wasn't required. It was designed for what's termed a "master/slave" luminaire arrangement where the (unswitched) power came in to one luminaire, thru the relay, then the spare channel was connected to a flex and socket for connection to an adjacent luminaire. This almost halved the cost of the C bus, yet retained individual control of every luminaire in an office!

That's the history - and why the devices are so "odd" - they were never intended as a "stand-alone" device, but rather to terminate 1.0mm cables inside a luminaire body. However, they are a very handy and cheap way of adding those few extra relay channels you often need in a DINrail installation, due to the far higher cost of the new Cbus2 devices.

Cheers, John

PS : After Cbus was released and started making an impact on the existing players, some opposition control companies really started pushing DIN mounted devices and used that as a strong "sales feature" against Clipsal, using all manner of arguments because of the Cbus approach making the system so much more affordable. Since Cbus was considered somewhat of the underdog at the time, they eventually bowed to that sales pressure and developed DIN rail mount devices with lots of channels - the old Cbus1 was replaced by C bus2 that we all know and love

Those sales pressures in the early-days are also the reason for silly products like the L5504RVF with 20A per channel, magnetic latching and manual over-ride handles. These features weren't really "required" by the market nor by Cbus, but rather that Clipsal needed a product to counter the sales pitches made by opposition companies (in that case, for the Sydney Olympic stadium against Thorn's "Watt4"). The opposition products were so unreliable that they *needed* to have the manual over-ride so you could switch on the lights when the control system comms (inevitably) failed !

I remember clearly a meeting where we were sitting around working out how to win that Stadium contract. We had a copy of the opposition's sales pritch and were working through it point by point to create a countering pitch. One point was that they used was that Magnetically Latched relay with manual over-ride, so that in the even of a comms failure you could still operate the lights - and my response was simply to say "Watt4" (get it? )

SHEESH - that was an long answer to a simple question !

 

John,


Many thanks for the fascinating insight into the history of the 'product'!



Greig.