Why do all automation controllers seem to have a maximum of 16 relay contact closures

[Andy Frodsham]

Looking at the specifications of various cinema automation controllers and I've noted that they all seem to have a limit of 16 relay contact closure outputs accessible from the projection server. Why this magic 16? Why not 24 or 32?

How do the large flagship theatres cope with this limit?

I know that some devices are controllable via the theatre network, but lighting, masking and curtain cues still use contact closure. Theatres with complex masking and lighting systems must be up against it when it comes to the 16 contact limit.

[Steve Guttag]

The EPRAD eCNA line will go beyond 16. The eCNA-5 comes with 16 (8 low-current, 8 high-current) but one can add an additional I/O board to bump that up to 32 relay outputs (and 16 inputs).

The eCNA-10 comes, in its most basic form, with 24 relay outputs (22 low-current, 2 high-current) but there is an optional daughterboard to add an additional 8 outputs (high current) and 8 inputs. One can also add up to two eCNA-5 I/O boards, with 16 relays each. So, you could go up to 64 relays...which is an insane number for just about any cinema to need that number of dedicated relay type closures.

Where you'll run out though are unique "flags" to control them. Unless I'm mistaken, it is the status flags that fire the relays. Nothing stops one from setting several relays to a common flag. So, for house lights up, one could have 4 relays for four different dimmers or dimmer zone all fired at once.

We use probably more relays that most because we have a high number of full masking customers (and often 2-4 masking systems per screen but the most popular are 1-2 masking motors). For theatres with a grand drape and full masking, I tend to start with the eCNA10 to ensure I have the relay count for it all. Most of the masking systems (MDI) use four control lines to set up to 10-stops (stops are via single or dual-button presses, nothing more).

Most complex lighting systems, nowadays, are via DMX or other form of network control, not contact closures. Even when I've interfaced with proprietary lighting systems, with scene presets, if they have an I/O interface box, one normally can only select 4-6 "scenes." For others, they have an Ethernet interface and we are back to just selecting scenes/presets via Ethernet.

You'll have a hard time justifying to any automation company that their standard automation will need a large number of relay outputs to satisfy what amounts to less than 1% of sales. I think Eprad's approach has been a good one...if you need the extra relays, expand the unit while the off-the-shelf version(s) will satisfy 99% of the rest.

[Sean McKinnon]

I will drop a jnior at each masking motor or in each screens amp rack to control masking and lighting either DMX or contact closure.

[Carsten Kurz]

JNIORs also have bus extendable relays. I rarely see any real need for more than e.g. 8 GPOs for auditorium control. We do actually use 12 from our Sony, but most of them are actually a backup towards the audio processor (which is usually controlled through IP).

[Steve Guttag]

I can see Sean's approach of one JNIOR per masking machine though it would seem a bit kludgy unless there is an overall automation system harmonizing it all. I think Integ has dropped the external relay module (probably due to lack of sales...which should tell you what the market is for high-quantity relay systems.

As for why we use so many relays...well. There are 4-8 of them on masking machines...possibly 2 on a grand drape. Depending on the dimmer systems used, there could be another 4-12 (if they are contact closure dimmers like Kelmar, and there are three zones...it adds up). We have several customers that use magnetic door latches on the theatre doors so one will have a relay on that (high current). We, typically, arrange for the automation to control the power to the projector (and server, if separate), possibly the sound rack (to a contactor) and projector exhaust. When the theatre is done for the day, the manager (or timer) will press the end of day and the server will gracefully shutdown and after that, the projector will power down. Some projectors, like NEC go to standby but that leaves a fan running too...which wears the fan and also sucks in more dirt (to the filter). We, mostly power it the rest of the way down. The Eprad eCNA automations just make all of that much easier. If one needs or wants a high relay count automation, even if augmenting another control system (like Q-SYS), the eCNA is hard to beat and it is one of the most reliable things I've ever dealt with. Our failure rate is near zero. Their part quality is also high. If you haven't checked it out, it is worth looking at.

Note, there is another cinema automation out there, the Pennywise, that Film-Tech uses. I don't know if Film-Tech sells it as a stand alone or just as part of their complete systems. However, due to its film heritage, it too should have a decent quantity of relays. the CA21 certainly had quite a few, though all low-current relays. Since I know F-T controls 120V things, I believe there is a relay interface board that gets them suitable relays/contracts.

[Marcel Birgelen]

Maybe I'm old-school, but I really like my power relays on an old-school Modbus:

- No practical limit on the amount of inputs and outputs
- Your main bus can be up to 700m and doesn't require fancy cabling.
- You can bring your power relays close to where the action is, this saves on expensive power cabling.
- You can extend Modbus over Ethernet/IP if you want, that gives you easy access to locations you otherwise would've had a hard time reaching via the main bus.
- Stuff just works, most PLCs I've installed outlasted the building...

[Steve Guttag]

Old school is cam timers and open-contact type relays (think pinball machines back in the 50-70s).

To a degree, what Sean brought up, using a JNIOR at each masking machine is similar. One is putting the relay where the controlled device is. Then, all one is doing is getting the control information to the localized automation (via GPO, RS232 or Ethernet). Note too, if one is using Q-SYS, and the amplifiers are behind the screen (same concept but with the audio), one also now has GPIO terminals behind the screen to get the information to masking machine or via relays or via the JNIOR.

I should point out, the eCNA-5 IO board does NOT need to be located by the rest of the automation. So, one could put one of them behind the screen with the masking machines, if desired. And then, just a 5-cond cable could be run (or 2-conductor plus 2-conductor/shield (power and control, to allow for the voltage drop due to the longer run.

What a cinema automation brings to the table that even a general purpose one doesn't is that typical cinema things are already figured out and translate extremely well from theatre to theatre. Remember, an automation is more than just a collection of relays (though that is one of their outputs). It has its own programs/macros that can lighten the load to other, user interfaces. I don't find myself having to alter my eCNA configurations much because there are many things common to all theatres. Even the start up/shutdown stuff. I have, in one site, an "All On/All Off" via the Q-SYS control system. What it really does is tell one of the eCNAs to shut down, which puts it on the eCNA buss so ALL automations can act on it. Each eCNA then checks to see if an ingest is in progress and delays shutdown until finished. It only took a single instance in Q-SYS to give the user the control and a single Virtual I/O in the eCNA to then spread that to ALL eCNAs in the complex. The start up/shutdown routines were already there on each automation anyway. One gets the benefit of commonality between systems (particularly within a single chain) as well as much customization as necessary.

[Bruce Cloutier]

One of the most lengthy discussions we've ever had at INTEG was about the proper mix of I/O. The JNIOR is also used in the monitoring markets (cloud stuff) where people question the limited number of digital inputs and analog I/O input capabilities (10V and 4-20ma... not audio). You can never have the perfect thing for anyone. JNIOR1 and JNIOR2 had built-in analog which would have been great for all of the 10V reference signal lighting applications.

We do have an expansion module for adding to the relay count. Presently we offer only the Power (10A) relay module (4ROUT). Steve seems to be remembering that we have stopped offering the signal relay version of the 4ROUT. We can actually build those if anyone absolutely wanted them. I have 4 of them sitting right here by my desk.

What limits the number of expansion modules is the power supplied by the JNIOR. The coils on those power relays take some milliamps. It adds up. We also have a 16 relay limit but only when mapping the external relays into the bit sequence. The unit with a simple application can address any number of expansion modules. And, if anyone ever really needed it you can power the modules separately with a 5VDC supply and do 100 relays. I've thought to offer a small adapter with a barrel jack for that purpose.

We would consider a big JNIOR with umpteen relays of all sorts but no one ever makes the case for it.

Then what about having SPDT and DPDT relays? Latching relays might be a good way to save energy. Alas... too many choices.

But, yeah, we usually side towards the multiple JNIOR approach.

[Andy Frodsham]

As an art house venue, we have eight contact closures purely dedicated to screen masking (each covering a combination of bottom and side masking settings). We are also using two contacts for screen tabs, two more for screen light dressing and a final four for auditorium house lighting. So, all our sixteen contact closures are used-up. We certainly could do with more (two for other masking settings, a couple for alarms, and several others for other functions.

I'm interested by your last comment, Bruce. Is it possible to use more that one JNIOR off a single projection server? Presumably as Ethernet devices (ours is presently connected via the serial connection) multiples may be added?

[Pete Naples]

Andy, yes it is perfectly possible to use mutliple Jniors controlled by one server. I've a few sites which work that way.

[Randy Stankey]

I don't know how true this is but I just assumed that electronic controllers have numbers of inputs/outputs in powers of two because of the number of memory bits needed to address them.

If you wanted to have more input/output slots, you'd need more bits/bytes of memory/programming space and you'd probably end up wasting most of it. You'd also need to make the circuitry more complex as well as the firmware necessary to manage that one extra port so much that it doesn't pay off.

Eight outputs would need two bytes of memory and the states of all of them can be addressed with a two-digit hexadecimal number, ranging from "00" to "FF". Sixteen outputs could be managed with four bytes and it would take a hex number from "0000" to "FFFF" to address them. If, for instance, you had seventeen outputs, you'd need to add another byte and you'd end up wasting most of it.

I have an alarm clock on my nightstand that has a snooze button that lasts for eight minutes. I wondered why, at first, until I realized that you can count up to eight with only four bits of binary. If you wanted to make the snooze alarm last for nine minutes, you'd probably have to waste another whole byte, only one bit of which would actually get used. That would add to the cost and complexity of the device, most of which would be thrown away, just for one extra minute of snooze time.

Even today, as electronics are cheaper than they were decades ago, it's still more expensive and difficult to add more components that it's still necessary to economize.

[Bruce Cloutier]

Randy is right that the number of bits per byte comes into play. For certain relay closure commands in various protocols the 16-bit word is used to mask the selection of relays to command and another 16-bit word defines the state (open or closed) of the selected relays. As various models of the JNIOR have differing numbers of internal relays (in groups of 4) any 4ROUT external relay modules are used to pad the remaining bits (also in groups of 4). However, you can continue to add relay modules and randomly access them using the module ID. This may take a bit of software tweaking some of which may already be there. It is the 1A power supply and the limit on the current supplied to the expansion bus that ultimately limits the number of relays. Those coils eat up milliamps.

As an alternative you can use multiple JNIORs. Sometimes that is an advantage as you can locate each JNIOR where you need it to reduce the wiring requirements. You need only extend the network to each. The JNIORs can also be made to communicate with each other. So with some additional application coding multiple JNIORs could even look to be just one at the media system. Essentially one can serve as a repeater. We have some application where the JNIORs cooperate with one another to achieve some goal.

With a little programming a JNIOR could easily be optimized to manage masking in response to generalized cues.

[Sean McKinnon]

Often, I will just install a jnior at the stage/screen and use it to control the masking and curtain motors. it works very well. With the MDI K series motors (and im sure other like ADC etc...) you can paralell the push button modules with the jnior and provide push button and server cue control and if youre using q-sys or crestron touch panel or web control. I have one site where we are controlling masking multiple roll down screens and multiple stage drape machines (sound curtains, black out curtains) and chain motors that truss with loudspeakers are attached to with Q-Sys/Servers and Jniors. We had to use one of the expansion modules and edited the plug-in with JSON to get the auto id of the expansion modules and trigger them like the 1-12 relays on jnior 412. Works really well and it was small enough we could run two network cables (always a spare) and mount the Jnior and expansion modules in the stage machine vendors rack under the stage.

[Randy Stankey]

In most of the shops I have worked in, the assembly line equipment is made up of separate modules or machines that are networked together to make it all of them behave as if they were one big machine. There are network lines between them to send signals back and forth such as "READY," "WORKING," and "ERROR."
(Just examples.) As each machine in the line sends signals, the other parts of the line respond accordingly.

Most of those lines work on relay logic or PLC but I can see where it would be useful for each machine/module have its own separate networked controller.

Imagine several lines in a shop that are all networked together so that, if an error or a breakdown occurs, other machines can act as backups. Instead of just one group of machines operating as if they are one, the whole shop might be able to work that way. Further, one person can monitor a whole factory from just one or two computer screens.

Imagine that a micro-computer about the size of a pack of cigarettes could be used to convert a line that works on relay logic to a fully automated system.
I bet that a half dozen JNIOR modules (or fewer) could be used to do that.

Imagine what a dozen JNIORs could do for an average movie theater if they were all networked together.

You could practically automate the popcorn poppers!

[Dave Macaulay]

How many would you want? For a typical cinema 8 is generally enough... 3 lighting, 2 masking, 2 for audio. Now with masking rare in new builds and sound controlled via network, we often only use the 3 for lighting. We did use a lot of expansion modules for curtains and door magnets but usually needed just one 8 relay Jnior.
We have been using the 412 lately because we don't ever use 8 inputs - or 4 really, one is needed for fire alarm shutdown if that's used (always in multiplexes but rarely in small independents).
So a costlier automation with many outputs would not appeal here.