| Lynx DMX SSR4 |
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 Designed by Robert Jordan (“RJ”) from DIY Light Animations, the SSR4 is designed to work in one of two modes: either as a standard SSR (that is, as a remote solid-state relay driven by four low-voltage lines) or as a stand-alone, four-channel DMX controller with solid-state relays. Merely change a jumper and the device can function in either mode.I adopted the SSR4 because of DMX’s inherent ability to daisy-chain. This means that instead of running a dedicated Cat5 cable to each SSR (think of a spoke-and-wheel arrangement; this is what I did in the 2008 distributed environment), a main cable can move from one SSR4 device to another, vastly reducing the amount of Cat5 cable necessary. This technique also cuts down on potential points of failure: if an individual DMX SSR4 doesn’t work, it can be swapped out with a properly configured substitute. In the vanilla SSR world, you're constantly worrying about whether the controller is at fault, the cable is at fault or the SSR is at fault. This was the main difference between the 2008 show subsequent shows: I eliminated all the vanilla SSRs and built a handful of new DMX SSR4s to fill in the gaps. But what is an SSR? First, let’s take the first three letters, which stand for “solid-state relay.” A relay, in this context, is an electrical switch that’s controlled by electricity. As the phrase implies, an SSR is different from a standard mechanical relay in that it uses no moving parts (as opposed to an electro-mechanical relay, where the contacts are physically moved by electromagneticism) – it uses semiconductors to switch on and off the electrical circuit. In what we do with synchronized Christmas lights, an SSR takes the signals from a computer that are meant to control a string of Christmas lights and it turns them on and off. The SSR is like a guy standing at a light switch – when the computer tells him to turn the lights on, he flips the switch; when it tells him to turn them off, he flips the switch again. That switch-flipping part is handled by what is called a TRIAC. Basically, when a small electrical signal (such as what our Christmas lighting controllers use) is sensed, the TRIAC flips the high-voltage switch, turning on the lights. When the small signal ends, the switch is flipped off. Of course, you want to be safe about this whole thing: you don’t want stray wall-current electricity travelling its way up the control circuit and frying components (not to mention the computer), so there are some safety elements built into an SSR that make it much less dangerous. First, there's a fuse – always a good idea, a fuse. (It probably should be noted here as well that I have all the lighting circuits on Ground Fault Circuit Interrupt [GFCI] devices, which are designed to lessen the likelihood that the lighting master – me – will get electrocuted.)  Further, the SSR isolates the control signals from the electricity that lights the lights with a device called an opto-isolator or optocoupler. So the high voltage of the lighting circuit is never directly in contact with the control circuit; it is isolated.Many light masters use this type of controller in conjunction with a Grinch or a 595. Each SSR is connected to the Grinch or the via a Cat5 cable and appropriate RJ45 connectors and is connected to the wall outlet with an extension cord. The SSRs sit near the lights they control and for the most part don't have extension cords attached to them, but sometimes they do (it all depends). But here at PacificaLights, we use the SSR4 with the DMX option, making it a small controller that decodes the DMX signal and then drives the SSR components directly, on the same board. Let’s take a look at what’s inside of a Lynx DMX SSR:
In 2007 and 2008, as I went about learning how to be a light master, I ran across Sean Bowf’s SSR how-to on ComputerChristmas.com, which pushed me in the direction of how I went about building my SSR enclosures. (It should be noted here that I have departed from RJ’s original design for the SSR4 enclosure and as such I use right-angle RJ45 connectors, not top-access.)Bowf uses the Carlon B232A, two-gang outlet box and merely rests the printed circuit board on the bottom of the box. Though this box is cheaper, I wanted to go with a sturdier box that would have a flat bottom surface on which I could mount stand-offs. I ultimately chose the Carlon A238 double-gang outlet box (shown to the right). The stand-offs (I use the plastic plugs that are designed to be inserted into holes in concrete and masonary in order to attach screws; the plugs are from Crown Bolt, No. 10 by one-inch “masonry light duty,” while the screws are No. Four sheet metal screws, three-quarters-inch long) allow me the opportunity to easily remove the printed circuit board should something untoward happen during the lighting season and I need to make repairs. They also give the RJ45 connectors on the board a solid feel when plugging in a Cat5 cable. The first thing I do is to cut off the nailer that juts out to the right-hand side of the Carlon box; I keep the vertical nailers, which I will use to mount the box as necessary. The Carlon A238 has a “knock-out” almost exactly where the stand-offs set the center RJ45 connector (if the printed circuit board is mounted in the center of the box). I remove the knock-out and with a multi-use rotary cutter tool (aka: Dremel), remove the little bit extra that needs to come out there and then I cut out a second hole for the other RJ45 connector. At this point, I also drill a hole for the power cord.  I got two dozen computer power cords on eBay for $20 back in the spring of 2008 and use those as SSR power cords. I cut off the female end and then cut the remainder in half, removing the outer insulation from the spare cord and using the underlying wires to connect the SSR4 to the electrical outlets.In winter 2007, the West Coast hardware chain Orchard Supply Hardware (OSH), had 15-amp, 115-volt wall outlets on sale for 35 cents each; I bought four dozen for the SSR projects. On the hot side of each outlet, the tab connecting the top outlet from the bottom outlet is cut away so that there are four separate circuits in each two-gang box. So the SSR4s and the outlets are wired together using the computer power cord wire; I tin the ends of both the SSR4 end of the wire and the outlet end of the wire to make sure no stray strands of wire accidentally cause a short. I mount the masonry plugs to the PCB with the No. Four x 3/4 machine screws. Then I apply a dab of adhesive – I’ve used both Gorilla Glue and Goop and prefer the Goop for this – to the bottom of the masonry plug. I place the PCB in the box where it lines up with the holes I cut and wiggle it around a bit. Then I pull the PCB out of the box, eyeball the spots were the plugs had sat and put a big glob of glue on those points. I then put the PCB back and make sure the plugs seat in the globs of glue. I allow it to dry overnight. After building up a Lynx DMX SSR4 and installing it in its Carlon box, I test the unit to make certain that it operates correctly. If I know where this unit is going to be used in the show, I also at this time program it with its start address, which tells it where it resides in the DMX universe. The Carlon box is then finished off with a standard ivory-colored, nylon wall plate cover. The wall plate covers are labeled with masking tape and felt-tip pen, telling me the type of channels each outlet controls and a label is affixed near the RJ45 connectors, indicating the name of the device and the DMX in and out (when working outside at night, the more labels the better). Most of these controllers are hidden outside and covered with black plastic garbage bags to be made water-resistant. Next in our block diagram of the 2009 show’s technology is the Lynx MR16. |