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Distance to sensor

Posted: Tue Sep 03, 2013 8:48 am
by The Doc
I know the distance can be important but I wonder about the detail

I'll have an arduino connected to a temperature sensor by about 20 metres of two core cable. Will that work as is or do I need to do something to overcome problems ?

Re: Distance to sensor

Posted: Tue Sep 03, 2013 9:08 am
by andrew
Which temperature sensor are you using?

Re: Distance to sensor

Posted: Thu Sep 05, 2013 8:50 am
by The Doc
It's all a learning experience at present. I want to produce a controller for a solar pool heater. I have an old sensor on the roof which would be my preferred option. I planned to connect through an analogue input and observe resistance so as to set boundaries in the program. If that didn't work I thought I'd just try a thermistor from Jaycar with some weatherproofing ?

Re: Distance to sensor

Posted: Thu Sep 05, 2013 11:16 pm
by andrew
The Doc wrote:It's all a learning experience at present. I want to produce a controller for a solar pool heater. I have an old sensor on the roof which would be my preferred option. I planned to connect through an analogue input and observe resistance so as to set boundaries in the program. If that didn't work I thought I'd just try a thermistor from Jaycar with some weatherproofing ?
The old sensor sounds fine, as you understand the resistances involved (and it still works!). Otherwise there's literally scores of options - wired, digital, wireless etc.

Re: Distance to sensor

Posted: Fri Sep 06, 2013 4:10 am
by hamster
I did something like that with a guy at work. We used digital sensors on a multi-drop setup.

http://dx.com/p/ds18b20-waterproof-digi ... ver-204290

We had about 10m of UTP out to the sensors.

It was controlling the pump for a solar pool heater. We had
- Ambient air temperature sensor
- Pool outlet sensor
- Pool inlet sensor
- Ambient light sensor.

Logic was a little like - is it bright enough? is it warm enough? Is the pool cool? If so, turn the pump on for 30 seconds.

Is the water coming back into the pool warmer than the outlet temp? If so keep the the pump running, if not wait for 30 minutes and try again

Turn the pump off when the pool is too hot, or inlet water is not warmer than the outlet.

We also had some logic to prevent the pump from cycling on and off too rapidly.