Hello,
I have made my own home alarm system that has a central unit and several "satellite" nodes all over the house. The communication relies on Cat5e cabling, which carry I2C, 1-Wire and power for the remote satellites.
The I2C bus is extended via a mesh of 82B96's and I've lowered the total pull-up resistance of 1-W in order to be able to communicate over aproximately 20m.
So, in each satellite, I have a few I2C and 1-w devices (mainly PCF8574's, PCF8581's and DS18B20's) and connected to it I have some sensors like PIR's and actuators like relays, buzzer or sirenes.
The pinout I've been using so far (without any problems) is the following:
RJ45 / Cat5e cabling:
1 - Green-White - GND
2 - Green - I2C SDA
3 - Orange-White - 12V
4 - Blue - I2C SCL
5 - Blue-White - GND
6 - Orange - INTERRUPT BIT (for the PCF8574's)
7 - Brown-White - 5V
8 - Brown - 1-W
If you noticed, all x-white conductors are power-related. Not sure if this would be a good design rule or not...
According to the Cat5e specifications, each conductor should be able to carry 500mA current (so enough to feed a couple of sattelites) and the number of twists per meter is different according to the colour we are talking about.
I'll now update my alarm system for "version 2" and I have the chance to change the cabling pin-out (although the current one is working fine).
Having this in mind, I'd like to ask the experts what would be the best theorethical pinout for the Cat5e cabling for carryng these signals in order to avoid as much as possible interference. Would my current pinout be the possible best, or would it be better if different (how and why?).
Let's open this discussion to the community!
Thanks in advance,
Jabss
I have made my own home alarm system that has a central unit and several "satellite" nodes all over the house. The communication relies on Cat5e cabling, which carry I2C, 1-Wire and power for the remote satellites.
The I2C bus is extended via a mesh of 82B96's and I've lowered the total pull-up resistance of 1-W in order to be able to communicate over aproximately 20m.
So, in each satellite, I have a few I2C and 1-w devices (mainly PCF8574's, PCF8581's and DS18B20's) and connected to it I have some sensors like PIR's and actuators like relays, buzzer or sirenes.
The pinout I've been using so far (without any problems) is the following:
RJ45 / Cat5e cabling:
1 - Green-White - GND
2 - Green - I2C SDA
3 - Orange-White - 12V
4 - Blue - I2C SCL
5 - Blue-White - GND
6 - Orange - INTERRUPT BIT (for the PCF8574's)
7 - Brown-White - 5V
8 - Brown - 1-W
If you noticed, all x-white conductors are power-related. Not sure if this would be a good design rule or not...
According to the Cat5e specifications, each conductor should be able to carry 500mA current (so enough to feed a couple of sattelites) and the number of twists per meter is different according to the colour we are talking about.
I'll now update my alarm system for "version 2" and I have the chance to change the cabling pin-out (although the current one is working fine).
Having this in mind, I'd like to ask the experts what would be the best theorethical pinout for the Cat5e cabling for carryng these signals in order to avoid as much as possible interference. Would my current pinout be the possible best, or would it be better if different (how and why?).
Let's open this discussion to the community!
Thanks in advance,
Jabss