Length of sensor wires

Projects General Guidance
1

Setting up a home automation system using Arduinos and have been wondering how long sensor wires should be as a maximum.

I'm planning to run the typical sensors off a number of arduino nodes reporting back to OpenHAB via MQTT (either via Ethernet - if I can find a reliable shield, or using nrf24 transceivers).

At the Arduino node, how long should the sensor cables sensibly be before they either become unreliable or introduce too much loss/resistance?

I'm looking at DHT22, barometric pressure, reed switches, PIR, smoke sensors, the usual...

Also, what kind of wire should I use? I have just wired the house up with CAT6 and have a box of that downstairs - does it make sense to use that for sensors, or would I be better off with something else?

2

It depends.

PIR sensors and reed contacts switch DC. You could transport that over 10Km or more.

High speed digital signals is another story.

Cat-6 cable is good in most cases. I use it succesfully for ~8meters of 100Khz I2C.

I guess you have to look at each sensor/data format individually.
Leo..