Step 4 : SSR-2009D Construction
I used the free ExpressPCB software to design the circuit board and www.expresspcb.com to etch them. After uploading the PCB data file and ordering via credit card, I received 8 boards for only $113 within 4 days. The boards were beautifully done, tinned and pre-drilled. I would use their service again in a heartbeat -- it is much easier and less hassle than etching your own.
While only four basic components are necessary to make a functional SSR circuit, the diagnostic LEDs make it easier to troubleshoot when lights don’t go on: if a channel’s LED doesn’t light, there’s a connection problem between the controller and the SSR while if the LED lights but the string doesn’t, then the problem is either with the light string itself or A/C power. Any inexpensive LEDs will suffice when you also use the R3 resistors (750 to 1K ohm work fine). The 6-pin IC sockets are nice but you can also solder the optocouplers directly to the board instead. The RJ45 connector is convenient if you plan to connect the SSR to your controller using Cat-3 or Cat-5 wire and a Cat-5 patch panel, but is otherwise unnecessary. RJ45 pins 2, 4, 6, and 8 are used for the +5v signal to the four channels; a standard Cat-5 cable using the common T568B wiring scheme means that pins 2-4-6-8 are solid orange, blue, green and brown respectively so it’s easy to wire. The T568A scheme means the same pins are solid green, blue, orange and brown instead. The SSR also connects pins 1-3-5-7 which are in turn connected to the controller’s ground. You can use commercial Cat-5 cables without modification if you wish.
An extra +5v connection point is added on the board for each of the channels if you are squeamish about soldering in the closeness of the RJ45 pins or don’t plan to use an RJ45 connector at all. Terminal blocks for the outputs are unnecessary if you plan to wire 110VAC directly to the SSR and the four 110v outputs. I snip the plugs off the light strings and use inexpensive wire nuts to connect the strings to the SSR OUT leads. Because a typical light string’s plug has a fuse built into it, I use one of them for the 110vac IN connection to the board to protect against shorts. Since a typical 100-light string uses about 1/3 amp, the 8-amp triacs can easily accommodate up to 3 strings each (about 1amp per triac) and about 4 amps per 4-channel SSR when all lights are on. Theoretically, a standard household 20-amp circuit could handle up to five 4-channel SSRs at once for a total capacity of 60 light strings all lit simultaneously. Theoretically. I’ve never tested 60 on one circuit in actual practice.
