Step 26 : RJ45 Interface


Clarification: This design will work just fine with Cat5e or Cat5. But the color scheme demonstrated below is for Cat5 NOT Cat5e. Just make sure you follow the NUMBERS if you are doing Cat5e. The colors are only correct for CAT5.

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For this design:
Pair 1 = RS485 B is Blue(4), RS485 A is Blue-white(5)
Pair 2 = Orange(6) and Orange-White(3) are spares. (ZC in the future?) I have placed traces on the board such that a solder ball could be added to make these additional power and ground if needed. They probably will not be necessary given the low DC power consumption of the board. But you could solder them to make this board 100% RJ45 pin-out compatible with other co-op boards. In the easily modified case, Pin 3 becomes VCC, Pin 6 becomes ground. Even without this solder ball this board should still work in series with other Renard boards, it would just remove one of the power supply pins from the picture downstream from this board if you didn’t make the change. In short: these could be used for anything you like. Look for via’s labeled “3” and “6” near both RJ45 connectors.
Pair 3 = Green-white(1) and green(2) for ground (intuitive)
Pair 4 = Brown(8) and Brown-white(7) for >9 VDC < 15VDC (Input to 5V regulator). The reason the <15VDC rule is imposed is due to the use of the ESD protection MOV device listed in the parts list. If you use this MOV it has a maximum continuous operating voltage of 18VDC, thus I suggest never going over 15VDC continuously applied via the RS45 interface.

Step 27 : ESD

The parts list assumes you will install RS485 chips that have electro static discharge protection (ESD). However, if you choose RS485 parts that do not have ESD protection, or you wish to install your own ESD devices for any other reason, this section will explain how to do so.

ESD2, ESD3
One option in this design is to install surface mount electro static discharge protection to protect the interfaces called “PESD” (Polymer ESD). On the bottom side of the board, near the A/B pins of both the input and output RS485, and underneath the RJ45 connectors, there are surface mount regions labeled ESD1 through ESD4.

Please note the “+” or “-“ which indicate the VCC and VSS sides of the region respectively. Some ESD components may have a + and – side (polarized). In each RS485 ESD region you may choose to install an ESD device for RS485-A and ESD device for RS485-B. The A and B signals should go through one ESD device to GND. In the picture above, the surface mount components would be mounted vertically.

ESD1, ESD4
Even if you use RS485 parts that have ESD protection features, the 12VDC power rail will still be unprotected. There are ESD pads below the RJ45 connectors. They can optionally be loaded with a MOV (Metal Oxide Varistor), between the 12VDC rail, and the GND rail. This will protect the 12V power rail from ESD.

It should be noted that the sole purpose of this ESD protection is to protect the interfaces of the controller, that is, the RJ45 connections only. These ESD countermeasures assume that the ESD pulse is originating from the RJ45 connector. If you have a static charge on your finger, and touch the controller, you may still cause damage. Every time you open up your controller box, and you need to touch something (First make sure the AC power is disconnected) you should momentarily touch your finger to TP1, the test pin that goes to ground to discharge yourself.

Step 28 : Future Design Compliance

The following is a list of the minimum requirements desired in order to be compliant with the other boards that have been made, and therefore increase the value to all developers:
1. Output pin numbering of channels should be 1 to 8 linearly, no mixing up the numbers
2. It would be optimal if designs would take both RS232 and RS485 as input.
3. Debug features, LEDs, switches, etc
4. Work closely with Phil and others to insure your implementation of the pins on the RJ45 port will work with other designs.

Step 29 : Future Design Desires

1) Add status LEDs (for the PIC, not for each channel).
2) Lamp test switch.
3) Add external clock (for higher baud rates).
4) On-board programming capabilities. There are two possibilities here - add hardware from one of the el-cheapo designs so that you could start with a blank PIC, or use the code-Flash design which starts initially with a pre-programmed PIC).
5) Change to RS485 interface (requires some sort of controller to connect the PC to the dimmers).
6) DMX compatibility (full compatibility requires RS485 interface, different connectors, and some way explicit method of assigning an address to each PIC chip, and some non-trivial firmware changes). Again, this requires some sort of controller between the PC and the dimmers.

7) Bi-directional communications (the hardware part of this should be added when incorporating the RS485 interface), to enable adding some of the more advanced software features.

Step 30 : Additional Resources

The main place to find support specifically for PIC based Christmas light controllers
http://picdimmer.17.forumer.com

The preferred software used with this setup
http://vixenlights.com/

Another good resource for how-to’s and information related to Christmas light controllers
http://computerchristmas.com/