Sensors on phone lines?

Hi,

I'm running a number of DS18B20 therms around the house and in some cases, i've utilised spare pairs on the phone extension wiring.

I'm sending 5v, GND and the data pin for the therms down the same cable as the phone extensions which only use 1 pair of wires.

It's a mixture of cat5 that I have run and normal, un-twisted phone extension cable put in by the builders.

It seems to work and I dont think there is any noise on the phone line when I listen to it....

Just wanted to check though, is there anyone with more electronic knowledge who can comment if this is a sane thing to do or whether there is a reason I shouldn't?

Thanks,

Ian

There is allways a risk of a short and I recall that phonelines can have 50 Volt or so (no expert) on them so it would kill quite some Arduino's and sensors.

If the phoneline is laid in a separate plastic tube the easiest safe thing to do imho is put an extra cable through. That is isolated better at least.

Best option is to use a dect phone so you have all your phone cables free for sensors :)

Hi,

Thanks for that.

I assume the interference from the ringer will not be destructive or dangerous but will show up in the form of not been able to get readings from those sensors while the phone is ringing?

Ill have to give it a try and see if I can make it happen.

Thanks,

Ian

I'm rather surprised it worked. ;) How many feet is the total run and what resistors did you use? How many devices?

You didn’t mention how frequently you are taking readings, but there are several ways of mitigating any potential problems. You could sense when the phone is ringing and hold off taking any readings until it stops. Or you could keep running averages and throw out “outlying” readings, etc.

At the moment it’s running a web server but i’m going to make it loop round and upload externally with a GET request every 5 mins…

Thanks,

Ian